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1.
Hoffmann, David.
High harmonic generation using multicolour fields.
Degree: PhD, 2011, Imperial College London
URL: https://doi.org/10.25560/9149 
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543355
► This thesis describes the phenomenon of high harmonic generation from atoms irradiated by intense, ultrashort laser pulses. Particular attention is paid to the benefits achieved…
(more)
▼ This thesis describes the phenomenon of high harmonic generation from atoms irradiated by intense, ultrashort laser pulses. Particular attention is paid to the benefits achieved by using multicolour driving fields. A theoretical description of few-cycle laser pulses is presented, together with their interaction with free-electrons and the role they play in various nonlinear optical processes. A number of numerical models are presented to simulate high harmonic generation from atomic systems. These are used to analyse and explain the temporal structure of the emitted high-frequency dipole radiation. Propagation of the macroscopic harmonic response through a gaseous volume is modelled and the role of phase-matching explained in detail. We consider focussing geometry in optimising the yield of particular harmonics, together with the effects of free-electrons within the interaction region. We discuss means by which multicolour fields may overcome some of the constraints of single-colour high harmonic generation. Using two delayed pulses of the same frequency and parallel polarisation we demonstrate significant cut-off extension without increasing total ionisation throughout the pulse, crucial for maintaining harmonic yield close to the saturation limit. We also explain the significant yield enhancements observed in recent experiments using two parallel colours of incommensurate frequency. Finally, we describe the use of a second, perpendicularly polarised colour in trajectory selection, allowing for a temporal filtering of harmonic emission. Using an ω + 1.5ω frequency ratio also allows for a reduction in the periodicity of emitted attosecond pulse trains, permitting the production of isolated attosecond pulses with longer driving fields. Furthermore, by controlling the relative phase between the two colours, the ellipticity of these attosecond pulses may also be controlled.
Subjects/Keywords: 535
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APA (6th Edition):
Hoffmann, D. (2011). High harmonic generation using multicolour fields. (Doctoral Dissertation). Imperial College London. Retrieved from https://doi.org/10.25560/9149 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543355
Chicago Manual of Style (16th Edition):
Hoffmann, David. “High harmonic generation using multicolour fields.” 2011. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
https://doi.org/10.25560/9149 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543355.
MLA Handbook (7th Edition):
Hoffmann, David. “High harmonic generation using multicolour fields.” 2011. Web. 04 Mar 2021.
Vancouver:
Hoffmann D. High harmonic generation using multicolour fields. [Internet] [Doctoral dissertation]. Imperial College London; 2011. [cited 2021 Mar 04].
Available from: https://doi.org/10.25560/9149 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543355.
Council of Science Editors:
Hoffmann D. High harmonic generation using multicolour fields. [Doctoral Dissertation]. Imperial College London; 2011. Available from: https://doi.org/10.25560/9149 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.543355
2.
Wee, Wei Hsiung.
The physics of negative refraction and transformation optics.
Degree: PhD, 2011, Imperial College London
URL: https://doi.org/10.25560/8996
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540647
► Whilst optics is one of the oldest field in science, there are still aspects of electromagnetism that we are only beginning to uncover. For instance,…
(more)
▼ Whilst optics is one of the oldest field in science, there are still aspects of electromagnetism that we are only beginning to uncover. For instance, it was demonstrated that materials with simultaneously negative permittivity and permeability exhibit certain exotic behavior; where familiar physical phenomena, such as refraction, are reversed. As such, these materials came to be known as negative refractive index materials (NRIM) and their collective properties as negative refraction. One of the most important and remarkable property of NRIM is perfect lensing - the ability to transport both supra and sub-wavelength optical information from one surface (object plane) to another (image plane), forming images with unprecedented resolution, beyond the diffraction limit. Perfect lensing itself is a consequence of deeper symmetries in electromagnetism, encapsulated in the language of transformation optics - with which we have both a descriptive tool to unify diverse electromagnetic configuarations, as well as a prescriptive tool to design media which bends light at will. While, such transformation medium and NRIM have been demonstrably realised using metamaterials, several challenges remain, of which loss is the major challenge. It is therefore under this trinity of concepts: metamaterials, negative refraction and transformation optics that this thesis is presented. In particular, this thesis illustrates the convergence of the later two concepts, giving rise to a novel class of perfect lens - the compact perfect lens. Here, we shall investigate, their unique properties, construction, challenges, and the dynamics of these lenses. In particular the formulation to study dynamics and effects of losses, is universal; applicable to lenses of any geometry. Finally we shall also propose an alternative universal, top-down approach to overcome losses in perfect lenses using phase conjugation, and demonstrate the capacity of such lenses to see through lossy, translucent obstacles.
Subjects/Keywords: 535
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APA (6th Edition):
Wee, W. H. (2011). The physics of negative refraction and transformation optics. (Doctoral Dissertation). Imperial College London. Retrieved from https://doi.org/10.25560/8996 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540647
Chicago Manual of Style (16th Edition):
Wee, Wei Hsiung. “The physics of negative refraction and transformation optics.” 2011. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
https://doi.org/10.25560/8996 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540647.
MLA Handbook (7th Edition):
Wee, Wei Hsiung. “The physics of negative refraction and transformation optics.” 2011. Web. 04 Mar 2021.
Vancouver:
Wee WH. The physics of negative refraction and transformation optics. [Internet] [Doctoral dissertation]. Imperial College London; 2011. [cited 2021 Mar 04].
Available from: https://doi.org/10.25560/8996 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540647.
Council of Science Editors:
Wee WH. The physics of negative refraction and transformation optics. [Doctoral Dissertation]. Imperial College London; 2011. Available from: https://doi.org/10.25560/8996 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540647
3.
Woodhead, Christopher Stephen.
Enhancing the light output of solid state emitters.
Degree: PhD, 2017, Lancaster University
URL: https://doi.org/10.17635/lancaster/thesis/130
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727153
► The work in this thesis focuses on improving the light output of room temperature emitting materials, and nanostructures as a stepping stone for use as…
(more)
▼ The work in this thesis focuses on improving the light output of room temperature emitting materials, and nanostructures as a stepping stone for use as single photon sources. The primary nanostructures studied are III-V based type-II emitting quantum dots/quantum rings (QDs/QR’s), which emit at telecom wavelengths either in the O-band (GaSb/GaAs QRs) or the C-band (InAs/GaAs QDs capped with GaAsSb). Individual exciton emission at low temperature was observed in these samples using micro-photoluminescence for what we believe is the first time. This was achieved by reducing the excitation area of the sample using micropillars and gold aperture masks, combined with increasing the extraction efficiency of light using a solid immersion lens. The observation of individual exciton emission enabled their contribution to the power dependent blueshift of type-II quantum dots to be studied. The integration of the InAs/GaAs QDs with silicon was explored by studying their emission when they are grown on both GaAs and silicon substrates. Studies such as this are an important step towards integrating QDs with on-chip communications. Finally, solid immersion lenses formed from a UV-curable epoxy are explored as a method for increasing light out of 2D materials. It was found that for Tungsten Diselenide (WSe2) the solid immersion lens increased the intensity of the emitted photoluminescence, as well as preventing the monolayer from degrading. This method could prove to be an excellent method for increasing the light output of 2D material based LED’s, especially WSe2 based single photon sources.
Subjects/Keywords: 535
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APA (6th Edition):
Woodhead, C. S. (2017). Enhancing the light output of solid state emitters. (Doctoral Dissertation). Lancaster University. Retrieved from https://doi.org/10.17635/lancaster/thesis/130 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727153
Chicago Manual of Style (16th Edition):
Woodhead, Christopher Stephen. “Enhancing the light output of solid state emitters.” 2017. Doctoral Dissertation, Lancaster University. Accessed March 04, 2021.
https://doi.org/10.17635/lancaster/thesis/130 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727153.
MLA Handbook (7th Edition):
Woodhead, Christopher Stephen. “Enhancing the light output of solid state emitters.” 2017. Web. 04 Mar 2021.
Vancouver:
Woodhead CS. Enhancing the light output of solid state emitters. [Internet] [Doctoral dissertation]. Lancaster University; 2017. [cited 2021 Mar 04].
Available from: https://doi.org/10.17635/lancaster/thesis/130 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727153.
Council of Science Editors:
Woodhead CS. Enhancing the light output of solid state emitters. [Doctoral Dissertation]. Lancaster University; 2017. Available from: https://doi.org/10.17635/lancaster/thesis/130 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.727153
Universitat Politècnica de Catalunya
4.
Yudistira, Didit.
Micro-structured ferroelectric superlattice for efficient acousto-optic devices.
Degree: 2012, Universitat Politècnica de Catalunya
URL: http://hdl.handle.net/10803/81500
► In this thesis we have investigated and proposed acoustic superLattices (ASLs) made of periodically poled ZX-cut lithium niobate (PPLN) associated ith coplanar electrodes as an…
(more)
▼ In this thesis we have investigated and proposed acoustic superLattices (ASLs) made of periodically poled ZX-cut lithium niobate (PPLN) associated ith coplanar electrodes as an effective alternative for surface acoustic wave (SAW) generation. In order to examine the acoustic transduction in the SL transducer we have developed and employed two modeling techniques. i.e . scalar approximation and finite element method (FEM) analysis (2-D nd 3-D modeling) implemented in COMSOL MULTIPHYSICS. Both techniques give similar results with respect to the characteristics of generated
SAW modes. The calculated results obtained with the 3-D FEM simulation confirmed the Rayleigh nature of the generated SAW, showing that the
excited SAW in the ASL is similar to that of the standard interdigitated transducer (IDT). From the propagation analysis in 2-D FEM simulation. we obtained that in addition to the SAW, the ASL transducer excites longitudinal bulk acoustic wave (L-BAW). Moreover. the 2-D model showed that the
SAW excited by the ASL transducer does not propagate but it is rather confined within the transducer.
Several ASL transducers, with different lattice periods, have been realized and characterized, also to validate the modeling and design tools . One and two-portelectrical measurements have been performed to evaluate the electro-acoustic response. In addition laser interferome try has been carried out o determine the out-of-plane component of the SAW displacement. With respect to the standard IDT configuration using the same crystal orientation, he efficiency of the SAW generation in the proposed designs is similar, while, for the same grating period, the resonance frequency that can be achieved is two times larger. In addition to the SAW, unlike its lOT counterparts, the ASL transducer can excite the L-BAW, as it had been predicted by the modeling. The two-port measurements have shown that the SAW signal collected at the receiver is small, indicating that the SAW energy remains essentially confined within the transmitter. This experimental result too is in agreement with the aforementioned theoretical predictions.
After the experimental validation of the modeling, we designed and fabricated acousto-optic (AO) filters incorporating the ASL transducer. ASL struc tures with 20 tm period and coplanar electrodes have been realized along with 6 m wide Ti-LiNb03 optical channel waveguide. In that way monolithic and integrated (waveguide) SAW based AO filters and L-BAW based bulk AO filters have been demonstrated. As for integrated SAW based
0 filter, a 3-dB optical bandwidth of 2.5 nm, center wavelength of 1456 nm, and -20 dB distance of 14.49 nm are obtained at the SAW resonance
frequency of 189.94 MHz. Such filter requires 1 W RF power to achieve nearly complete polarization conversion. As for the bulk AO filter. a center Wavelength of 1472.5 nm is measured at the L-BAW resonance frequency of 328 MHz. In the bulk AO filter. full conversion cannot be reached even at
RF power up to 2 W. Comparing to the integrated…
Advisors/Committee Members: Universitat Politècnica de Catalunya. Institut de Ciències Fotòniques, [email protected] (authoremail), false (authoremailshow), Pruneri, Valerio (director), Janner, Davide (codirector), true (authorsendemail).
Subjects/Keywords: 535
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APA ·
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Yudistira, D. (2012). Micro-structured ferroelectric superlattice for efficient acousto-optic devices. (Thesis). Universitat Politècnica de Catalunya. Retrieved from http://hdl.handle.net/10803/81500
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Yudistira, Didit. “Micro-structured ferroelectric superlattice for efficient acousto-optic devices.” 2012. Thesis, Universitat Politècnica de Catalunya. Accessed March 04, 2021.
http://hdl.handle.net/10803/81500.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Yudistira, Didit. “Micro-structured ferroelectric superlattice for efficient acousto-optic devices.” 2012. Web. 04 Mar 2021.
Vancouver:
Yudistira D. Micro-structured ferroelectric superlattice for efficient acousto-optic devices. [Internet] [Thesis]. Universitat Politècnica de Catalunya; 2012. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10803/81500.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Yudistira D. Micro-structured ferroelectric superlattice for efficient acousto-optic devices. [Thesis]. Universitat Politècnica de Catalunya; 2012. Available from: http://hdl.handle.net/10803/81500
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
5.
Tura i Brugués, Jordi.
Characterizing entanglement and quantum correlations constrained by symmetry.
Degree: 2015, Universitat Politècnica de Catalunya
URL: http://hdl.handle.net/10803/317393
► El entrelazamiento y las correlaciones no-locales constituyen dos recursos fundamentales para el procesamiento cuántico de la información, ya que abren la posibilidad de realizar tareas…
(more)
▼ El entrelazamiento y las correlaciones no-locales constituyen dos recursos fundamentales para el procesamiento cuántico de la información, ya que abren la posibilidad de realizar tareas que serían imposibles en el sentido clásico. Sin embargo, su elusiva caracterización aún representa uno de los problemas más importantes en la teoría cuántica de la información. La razón principal por la que una cuestión tan básica sigue siendo un reto formidable subyace en el incremento exponencial de la complejidad del espacio de Hilbert, así como del espacio de las correlaciones no-locales. Por otro lado, los sistemas físicos de interés muestran simetrías que pueden ser aprovechadas para reducir dicha complejidad, abriendo la posibilidad que, para tales sistemas, algunas de esas cuestiones devengan tratables. La presente tesis doctoral está enfocada al estudio de la caracterización del entrelazamiento cuántico y las correlaciones no-locales bajo simetrías. Contiene resultados originales en las siguientes líneas de investigación: entrelazamiento del tipo PPT en estados simétricos, detección de no-localidad en sistemas de muchos cuerpos, la no equivalencia entre el entrelazamiento cuántico y la no-localidad y las correlaciones monogámicas elementales. En primer lugar, estudiamos el entrelazamiento del tipo PPT en estados totalmente simétricos de n bits cuánticos. Resolvemos el problema abierto referente a la existencia de estados PPT entrelazados de cuatro bits cuánticos de este tipo, proporcionando ejemplos y métodos constructivos. Además, desarrollamos criterios de separabilidad, estados frontera y número de Schmidt para estados PPT entrelazados y simétricos. Nos centramos en la caracterización de estados extremos dentro de esta familia y proporcionamos un algoritmo para encontrar estados cuánticos con tales propiedades. En segundo lugar, estudiamos la no-localidad en sistemas de muchos cuerpos. Consideramos desigualdades de Bell, invariantes bajo permutaciones o traslaciones, que involucran correladores entre dos cuerpos como mucho. Dichas desigualdades constituyen los primeros tests de detección de no-localidad en sistemas de muchos cuerpos que son accesibles experimentalmente, con el presente nivel de tecnología. Además, demostramos cómo esas desigualdades de Bell pueden detectar no-localidad en estados físicamente relevantes, como los estados de mínima energía de hamiltonianos que aparecen en física nuclear. Proporcionamos clases analíticas de desigualdades de Bell y caracterizamos, también analíticamente, qué estados y medidas son los más adecuados para ellas. Vemos que el método que introducimos es generalizable a cualquier escenario de Bell. Finalmente, comentamos aspectos de interés desde un punto de vista experimental. En tercer lugar, demostramos que el entrelazamiento y las correlaciones no-locales son conceptos no equivalentes en general, resolviendo un problema que persistía abierto en el caso multipartito. Probamos que la forma más fuerte de entrelazamiento no implica la forma más fuerte de no-localidad en ningún…
Advisors/Committee Members: Universitat Politècnica de Catalunya. Institut de Ciències Fotòniques, [email protected] (authoremail), false (authoremailshow), true (authorsendemail).
Subjects/Keywords: 535
Record Details
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Record Details
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APA ·
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MLA ·
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Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Tura i Brugués, J. (2015). Characterizing entanglement and quantum correlations constrained by symmetry. (Thesis). Universitat Politècnica de Catalunya. Retrieved from http://hdl.handle.net/10803/317393
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Tura i Brugués, Jordi. “Characterizing entanglement and quantum correlations constrained by symmetry.” 2015. Thesis, Universitat Politècnica de Catalunya. Accessed March 04, 2021.
http://hdl.handle.net/10803/317393.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Tura i Brugués, Jordi. “Characterizing entanglement and quantum correlations constrained by symmetry.” 2015. Web. 04 Mar 2021.
Vancouver:
Tura i Brugués J. Characterizing entanglement and quantum correlations constrained by symmetry. [Internet] [Thesis]. Universitat Politècnica de Catalunya; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10803/317393.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Tura i Brugués J. Characterizing entanglement and quantum correlations constrained by symmetry. [Thesis]. Universitat Politècnica de Catalunya; 2015. Available from: http://hdl.handle.net/10803/317393
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Universitat Politècnica de Catalunya
6.
Gündoğan, Mustafa.
Solid-state quantum memory for photonic qubits.
Degree: 2015, Universitat Politècnica de Catalunya
URL: http://hdl.handle.net/10803/322551
► Les memòries quàntiques òptiques (MQs) son un dels elements fonamentals en la ciència de la informació quàntica (CIQ). El seu ús podria ser important en…
(more)
▼ Les memòries quàntiques òptiques (MQs) son un dels elements fonamentals en la ciència de la informació quàntica (CIQ). El seu ús podria ser important en aplicacions relacionades amb la comunicació i la computació quàntiques. Els ions de terres rares (ITRs) han sigut investigats durant dècades per les seves propietats òptiques. Exhibeixen excel·lents propietats de coherència quan es refreden a temperatures criogèniques. Per tant, no es sorprenent que hagin emergit com a candidats per ser usats en la CIQ com a MQs. En aquesta tesis, hem investigat l'emmagatzematge quàntic de qubits fotònics en un cristall de Pr3+:Y2SiO5 (PrYSO) per al seu possible ús en aplicacions relacionades amb xarxes d'informació quàntiques. Vam començar construint el dispositiu experimental i sistemes làser des de zero, ja que el nostre grup de recerca acabava de néixer. Els primers experiments van incloure espectroscòpia del sistema de PrYSO per identificar les transicions electròniques més apropiades per als següents experiments de MQs. En tots els experiments vam utilitzar el protocol de memòria basat en una pinta de freqüències atòmiques (PFA). També vam desenvolupar complexes seqüències de polsos, necessàries per a la preparació òptica d'una PFA. En el primer experiment vam demostrar l'emmagatzematge de qubits fotònics de polarització codificats en estats coherents febles. Aquest emmagatzematge es va dur a terme en els estats excitats dels ions Pr3+ durant un temps d'emmagatzematge predeterminat de 500 ns. Aquesta fita no s'havia assolit abans degut a que l'absorció òptica del material depèn de la polarització llum. Vam aconseguir fidelitats d'emmagatzematge d'un 95% de mitjana les quals sobrepassen el millor valor que es pot aconseguir amb una estratègia de mesura i preparació provant per tant el caràcter quàntic de la nostra interfície. Per poder-se implementar de manera realista en xarxes quàntiques, una MQ hauria de tenir la capacitat de recuperar la informació en-demanda (en el moment que es desitgi). Com a primer pas, el nostre següent experiment va involucrar la transferència dels polsos d'entrada cap a i des de els nivells fonamentals hiperfins i longeus dels ions Pr3+, mitjançant polsos brillants. A més, duent a terme experiments d'interferència, vam demostrar que la coherència es preserva durant els processos d'emmagatzematge, transferència i recuperació. També vam demostrar l'emmagatzematge temporalment multimodal en els estats d'espín, de fins a 5 modes. En l'última part d'aquesta tesis vam demostrar una memòria quàntica d'estat sòlid basada en ones d'espín, amb qubits codificats en estats coherents febles al nivell d'intensitat de fotons individuals. Emmagatzemar i recuperar camps òptics al nivell de fotons individuals en estats fonamentals del sistema PrYSO és exigent perquè els potents polsos de control i el polsos dèbils d'entrada que s'emmagatzemen a la memòria estan separats per només 10.2 MHz. Els polsos de control creen soroll, la majoria consistent en decaïment de lliure inducció, fluorescència i dispersió en les…
Advisors/Committee Members: Universitat Politècnica de Catalunya. Institut de Ciències Fotòniques, [email protected] (authoremail), false (authoremailshow), De Riedmatten, Hugues (director), true (authorsendemail).
Subjects/Keywords: 535
Record Details
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Share »
Record Details
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Cite
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❌
APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Gündoğan, M. (2015). Solid-state quantum memory for photonic qubits. (Thesis). Universitat Politècnica de Catalunya. Retrieved from http://hdl.handle.net/10803/322551
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Gündoğan, Mustafa. “Solid-state quantum memory for photonic qubits.” 2015. Thesis, Universitat Politècnica de Catalunya. Accessed March 04, 2021.
http://hdl.handle.net/10803/322551.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Gündoğan, Mustafa. “Solid-state quantum memory for photonic qubits.” 2015. Web. 04 Mar 2021.
Vancouver:
Gündoğan M. Solid-state quantum memory for photonic qubits. [Internet] [Thesis]. Universitat Politècnica de Catalunya; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10803/322551.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Gündoğan M. Solid-state quantum memory for photonic qubits. [Thesis]. Universitat Politècnica de Catalunya; 2015. Available from: http://hdl.handle.net/10803/322551
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Universitat Politècnica de Catalunya
7.
Rojo Badenas, Pilar.
Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens.
Degree: Departament d'Òptica i Optometria, 2015, Universitat Politècnica de Catalunya
URL: http://hdl.handle.net/10803/322554
► Esta Tesis tiene como objetivo la propuesta de un método para la evaluación cuantitativa de la refracción periférica inducida en el ojo de un paciente…
(more)
▼ Esta Tesis tiene como objetivo la propuesta de un método para la evaluación cuantitativa de la refracción periférica inducida en el ojo de un paciente por una lente oftálmica. La motivación del trabajo radica en la importancia de este fenómeno en el progresión de la miopía y sus causas. La existencia de una refracción periférica hipermetrópica se ha relacionado directamente con la progresión de la miopía, y las lentes oftálmicas son el elemento compensador preferenteen niños y adolescentes, los sujetos más relevantes en cuanto al control de la progresión de l amiopía, en sí misma y como antesala d eotros problemas oculares más graves. Hasta la realización de esta Tesis no existía un método preciso, próximo a los métodos convencionales del diseño de lentes oftálmicas, que permitiera el cálculo de la refracción periférica inducida por la lente oftálmica y el análisi de los diseños de lente utilizados. Dicho diseño debe considerar tanto los efectos asociados a a óptica y la geometría del ojo, como al propio diseño de la lente compensadora. El método que se propone sigue una metodologia próxima a la del diseño convencional de lentes oftálmicas, sustituyendo el rol del centro de rotación del ojo por el de su punto nodal, y el rol de la esfera del remoto por lo qque se ha denominado la superfície conjugada de la retina (RCS, de retinal conjugate surface, en el texto). Con este enfoque se han implementado algoritmos detallados de trazado de rayos finito y generalizado que permiten el trazado detallado de rayos en un conjunto de direcciones alrededor de la fóvea. Los algoritmos de trazado generalizado permiten el análisis de lentes oftálmicas de manera más eficiente que el trazado intensivo típico del software de diseño óptico, utilizando el concepto de trazado de frente d eonda, que analiza las deformaciones del frente de onda que acompaña a un rayo principal. Dichos algoritmos se han implementado y validado para un conjunto de lentes oftálmicas de diferentes geometrías en un software científico estándard (Matlab(R)) como parte de los trabajos desarrollados en esta Tesis. Mediante el uso de los algoritmos descritos es posible calcular la superficie refractada que induceuna lente oftálmica. A continuación se hen desarrollado modelos teóricos y experimentales para la RCS que permiten tener en cuanta la variabilidad de patrones de refracción periférica existente, y se ha propuesto el uso de vectores de potencia (M J0 y J45) para el cálculo de la refracción periférica inducida por la lente, mediante la combinación de la superficie refractada por la lente y la modelada para una determinada RCS. Se presentan casos para lentes esféricas, asféricas y astigmáticas, para ojos miopes y emétropes, y en condiciones de infra y sobre refracción, mostrando la potencialidad del método propuesto para diseñar lentes que compensen simultáneamente la refracción foveal y la periférica, que mediante el método propuesto podrán optimizarse simultáneamente.
Advisors/Committee Members: [email protected] (authoremail), false (authoremailshow), Royo Royo, Santiago (director), true (authorsendemail).
Subjects/Keywords: 535
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APA (6th Edition):
Rojo Badenas, P. (2015). Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens. (Thesis). Universitat Politècnica de Catalunya. Retrieved from http://hdl.handle.net/10803/322554
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Rojo Badenas, Pilar. “Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens.” 2015. Thesis, Universitat Politècnica de Catalunya. Accessed March 04, 2021.
http://hdl.handle.net/10803/322554.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Rojo Badenas, Pilar. “Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens.” 2015. Web. 04 Mar 2021.
Vancouver:
Rojo Badenas P. Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens. [Internet] [Thesis]. Universitat Politècnica de Catalunya; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10803/322554.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Rojo Badenas P. Generalized ray tracing method for the calculation of the peripheral refraction induced by an ophthalmic lens. [Thesis]. Universitat Politècnica de Catalunya; 2015. Available from: http://hdl.handle.net/10803/322554
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
8.
Badioli, Michela.
Graphene optoelectronics from the visible to the mid-infrared.
Degree: 2015, Universitat Politècnica de Catalunya
URL: http://hdl.handle.net/10803/336097
► Desde su descubrimiento en 2004, el grafeno, una sola capa átomos de carbono en un retículo hexagonal, ha atraído un gran interés de la comunidad…
(more)
▼ Desde su descubrimiento en 2004, el grafeno, una sola capa átomos de carbono en un retículo hexagonal, ha atraído un gran interés de la comunidad científica debido a sus propiedades electrónicas, mecánicas y ópticas extraordinarias. Los primeros estudios se centraron en el transporte electrónico, pero en los últimos años estudios en el campo de la fotónica y de las propiedades optoelectrónicas del grafeno han suscitado un mayor interés. El objetivo de esta tesis es explorar el uso del grafeno para nuevos dispositivos optoelectrónicos, adoptando diferentes enfoques para mejorar la interacción del grafeno con la luz en un amplio rango espectral, desde el rango visible hasta el infrarrojo medio. Esto incluye la investigación de la interacción y la transferencia de energía entre un dipolo y una monocapa de grafeno cercana, así como trabajar en esquemas de fotodetección eficientes.
La alta movilidad electrónica, la absorción de banda ancha, la flexibilidad y las propiedades optoelectrónicas sintonizables (véase Capítulo 1) hacen que el grafeno sea extremadamente atractivo para el desarrollo de aplicaciones optoelectrónicas con nuevas propiedades funcionalidades.
En cuanto a los dispositivos, el punto de partida de los experimentos presentados en esta tesis son transistores de efecto de campo con diferentes geometrías, cuya fabricación y técnicas de caracterización se describen en el Capítulo 2. La capacidad de ajuste de las propiedades optoelectrónicas a través del control de la energía de Fermi es una característica esencial de los dispositivos, y se logra con la aplicación de un voltaje de puerta.
Nos dirigimos a ambos aspectos a la base de la optoelectrónica, es decir, el control de las propiedades ópticas con campos eléctricos y la modificación de magnitudes eléctricas, como la corriente con la luz incidente. Por tanto, la primera parte de la tesis (Capítulos 3, 4 y 5) se dedica al estudio de la nanofotónica y plasmónica del grafeno, mientras que la segunda parte se ocupa de fotodetección basada en grafeno (Capítulos 6, 7, 8 y 9).
En el Capítulo 3, se explican los principales conceptos del campo de la nanofotónica de grafeno, como la capacidad de ajuste eléctrico y el fuerte confinamiento de los plasmones 2D, así como el acoplamiento de un emisor óptico con los plasmones o pares electrón-hueco. Luego se presentan dos experimentos que muestran el control de la luz por medio de campos eléctricos estáticos. En el Capítulo 4 se muestra el control eléctrico de las vías de relajación de iones de erbio en las proximidades de una monocapa de grafeno: el flujo de energía a partir de los emisores se puede dirigir a pares electrón-hueco en el grafeno, a fotones y a plasmones cambiando el nivel de Fermi del grafeno. En el Capítulo 5 se presenta la excitación y el ajuste de plasmones de grafeno altamente confinados en el infrarrojo medio, activado mediante el dipolo de una punta de microscopia de campo cercano (Capítulo 5).
En el Capítulo 6 se revisan los fotodetectores de grafeno existentes y los principales mecanismos que…
Advisors/Committee Members: Universitat Politècnica de Catalunya. Institut de Ciències Fotòniques, [email protected] (authoremail), false (authoremailshow), Koppens, Frank (director), true (authorsendemail).
Subjects/Keywords: 535
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APA ·
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MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Badioli, M. (2015). Graphene optoelectronics from the visible to the mid-infrared. (Thesis). Universitat Politècnica de Catalunya. Retrieved from http://hdl.handle.net/10803/336097
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Badioli, Michela. “Graphene optoelectronics from the visible to the mid-infrared.” 2015. Thesis, Universitat Politècnica de Catalunya. Accessed March 04, 2021.
http://hdl.handle.net/10803/336097.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Badioli, Michela. “Graphene optoelectronics from the visible to the mid-infrared.” 2015. Web. 04 Mar 2021.
Vancouver:
Badioli M. Graphene optoelectronics from the visible to the mid-infrared. [Internet] [Thesis]. Universitat Politècnica de Catalunya; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10803/336097.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Badioli M. Graphene optoelectronics from the visible to the mid-infrared. [Thesis]. Universitat Politècnica de Catalunya; 2015. Available from: http://hdl.handle.net/10803/336097
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Universitat Politècnica de Catalunya
9.
Steinlechner, Fabian.
Sources of photonic entanglement for applications in space.
Degree: 2015, Universitat Politècnica de Catalunya
URL: http://hdl.handle.net/10803/336671
► Las correlaciones no locales de sistemas entrelazados son una característica inherente a la teoría cuántica que está fundamentalmente en desacuerdo con nuestra noción intuitiva de…
(more)
▼ Las correlaciones no locales de sistemas entrelazados son una característica inherente a la teoría cuántica que está fundamentalmente en desacuerdo con nuestra noción intuitiva de realismo y localidad. Además, el entrelazamiento es un recurso esencial en numerosos protocolos de comunicaciones cuánticas, como por ejemplo la teleportación cuántica o la criptografía cuántica, en esquemas metrológicos cuánticos y en computación cuántica. Todos estos esquemas cuánticos permiten mejoras significativas de rendimiento con respecto a sus homólogos clásicos, por lo tanto, parece previsible que en un futuro próximo veamos implementaciones comerciales de protocolos que utilicen fotones entrelazados. Un reto fundamental con el fin de lograr una implementación a escala global del entrelazamiento cuántico es su distribución a grandes distancias. A pesar de que los fotones son portadores ideales de información cuántica, su distribución a través de largas distancias está significativamente limitada por pérdidas. En la actualidad, las pérdidas introducidas por las fibras ópticas, la atenuación atmosférica, o la dificultad de obtener una línea de visión directa en enlaces terrestres limitan la distribución de entrelazamiento fotónico a varios cientos de kilómetros. La instalación de fuentes de fotones con correlaciones cuánticas en plataformas espaciales permitiría superar tales limitaciones de distancia. Esto no sólo daría lugar a la primera aplicación de protocolos de comunicación cuántica a escala mundial, sino que también daría la oportunidad de llevar a cabo un nuevo tipo de experimentos cuánticos en un marco de la relatividad general. Las fuentes de fotones entrelazados que podemos encontrar hoy en día en los laboratorios de óptica cuántica no están en general preparadas para ser usadas en entornos hostiles, como podría ser el espacio, ya sea por la utilización de láseres voluminosos, la necesidad de estabilizar interferómetros activamente o simplemente por tener una eficiencia insuficiente. Por lo tanto, un prerrequisito para lograr la implementación experimental de protocolos de comunicación cuántica a través de enlaces satelitales es el desarrollo de fuentes de fotones entrelazados que sean robustas, compatibles con operación espacial, y con alto brillo y visibilidad. En esta tesis se pretende conectar los experimentos de laboratorio en entrelazamiento cuántico y las aplicaciones en entornos operacionales desfavorables en el mundo real. Los principales resultados son: ¿ Fuentes de fotones entrelazados en polarización de alta eficiencia para la distribución de entrelazamiento a través de enlaces en espacio libre de larga distancia. Las fuentes son muy robustas y compactas, y utilizan únicamente componentes que son compatibles con estrictos requisitos de vuelo y operaciones espaciales. - Optimización de las propiedades espectrales y la eficiencia de acoplamiento a fibra monomodo de pares de fotones generados a través de spontaneous parametric down-conversion en titanil fosfato de potasio polarizado periódicamente. Los resultados…
Advisors/Committee Members: Universitat Politècnica de Catalunya. Institut de Ciències Fotòniques, [email protected] (authoremail), false (authoremailshow), Pruneri, Valerio (director), true (authorsendemail).
Subjects/Keywords: 535
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Steinlechner, F. (2015). Sources of photonic entanglement for applications in space. (Thesis). Universitat Politècnica de Catalunya. Retrieved from http://hdl.handle.net/10803/336671
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Chicago Manual of Style (16th Edition):
Steinlechner, Fabian. “Sources of photonic entanglement for applications in space.” 2015. Thesis, Universitat Politècnica de Catalunya. Accessed March 04, 2021.
http://hdl.handle.net/10803/336671.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
MLA Handbook (7th Edition):
Steinlechner, Fabian. “Sources of photonic entanglement for applications in space.” 2015. Web. 04 Mar 2021.
Vancouver:
Steinlechner F. Sources of photonic entanglement for applications in space. [Internet] [Thesis]. Universitat Politècnica de Catalunya; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10803/336671.
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
Council of Science Editors:
Steinlechner F. Sources of photonic entanglement for applications in space. [Thesis]. Universitat Politècnica de Catalunya; 2015. Available from: http://hdl.handle.net/10803/336671
Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation
University of Oxford
10.
Lancaster, Andrew James.
Absolute distance interferometry capable of long-term high frequency measurements of fast targets.
Degree: PhD, 2015, University of Oxford
URL: https://ora.ox.ac.uk/objects/uuid:d597a926-ba4c-4b25-b2b7-695faf88979d
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712454
► This thesis presents two novel absolute distance measurement techniques which expand the recently developed dynamic frequency scanning interferometry method [1][2][3]. Preliminary work to improve the…
(more)
▼ This thesis presents two novel absolute distance measurement techniques which expand the recently developed dynamic frequency scanning interferometry method [1][2][3]. Preliminary work to improve the frequency referencing of the techniques will also be reported. The first method was developed to eliminate gaps in the distance measurement which were present in previous approaches and is referred to as continuous frequency scanning interferometry (continuous FSI). This technique has been successfully demonstrated on stationary targets at a range of 2.5-5 m and moving targets at speeds around 2 mm/s and 8 mm/s. The second method is referred to as enhanced continuous FSI (enhanced CFSI). It addresses one of the main limitations of the continuous FSI technique by greatly increasing the allowable target motion speed. Proof of principle measurements of enhanced continuous FSI have been performed at speeds of up to 16 mm/s and are presented here. The improved frequency referencing technique uses an optical nanofibre to perform saturated absorption spectroscopy of acetylene-13. The equipment, experimental procedure and preliminary results are presented.
Subjects/Keywords: 535
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Export
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APA (6th Edition):
Lancaster, A. J. (2015). Absolute distance interferometry capable of long-term high frequency measurements of fast targets. (Doctoral Dissertation). University of Oxford. Retrieved from https://ora.ox.ac.uk/objects/uuid:d597a926-ba4c-4b25-b2b7-695faf88979d ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712454
Chicago Manual of Style (16th Edition):
Lancaster, Andrew James. “Absolute distance interferometry capable of long-term high frequency measurements of fast targets.” 2015. Doctoral Dissertation, University of Oxford. Accessed March 04, 2021.
https://ora.ox.ac.uk/objects/uuid:d597a926-ba4c-4b25-b2b7-695faf88979d ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712454.
MLA Handbook (7th Edition):
Lancaster, Andrew James. “Absolute distance interferometry capable of long-term high frequency measurements of fast targets.” 2015. Web. 04 Mar 2021.
Vancouver:
Lancaster AJ. Absolute distance interferometry capable of long-term high frequency measurements of fast targets. [Internet] [Doctoral dissertation]. University of Oxford; 2015. [cited 2021 Mar 04].
Available from: https://ora.ox.ac.uk/objects/uuid:d597a926-ba4c-4b25-b2b7-695faf88979d ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712454.
Council of Science Editors:
Lancaster AJ. Absolute distance interferometry capable of long-term high frequency measurements of fast targets. [Doctoral Dissertation]. University of Oxford; 2015. Available from: https://ora.ox.ac.uk/objects/uuid:d597a926-ba4c-4b25-b2b7-695faf88979d ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712454
University of Oxford
11.
Pulampong, Thapakron.
Ultra-low emittance lattice design for advanced synchrotron light sources.
Degree: PhD, 2015, University of Oxford
URL: http://ora.ox.ac.uk/objects/uuid:092de1c4-f168-4014-a447-778f0c34360c
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712059
► Storage ring based synchrotron light sources deliver high brightness radiation generated by high quality electron beam. The electron beam emittance plays an importance role in…
(more)
▼ Storage ring based synchrotron light sources deliver high brightness radiation generated by high quality electron beam. The electron beam emittance plays an importance role in controlling the brightness and coherence of the radiation output. An extensive design effort is required to optimse the lattice to improve the beam emittance and machine performance. This thesis reports a series of investigations into lattice tuning, modification and full upgrade to improve the machine performance of third generation light sources, using the Diamond storage ring lattice as a model. In the first part of this thesis, the optics functions of the existing lattice are optimised in order to reduce the natural beam emittance. A reduction of 27% is achieved and verified experimentally, although the effects of strong insertion devices (IDs) reduce this improvement. A second study was carried out with the aim of replacing one of the existing double bend achromat (DBA)cell with one and two double-double bend achromat (DDBA) cells providing additional straight sections for IDs. It was proven that the addition of one DDBA cell can be implemented without significant deterioration of the performance of the machine. The case with two DDBA cells however provides a beam lifetime which is only half of the value in the existing machine. A third study was carried out to consider a full lattice upgrade using multibend achromat (MBA) cells aiming for ultra-low emittance. The last part of this thesis concentrates on the study of an improved beam injection scheme employing a pulsed multipole kicker (PM). The aim is to achieve an eficient beam injection while producing a lower perturbation to the stored beam during the injection. Based on particle tracking, the beam injection performance of the scheme is optimised for the existing Diamond and for the one DDBA lattice. The effects of the PM on the stored beam is proven to be negligible. The compatibility of the existing injection system with the new injection scheme is evaluated. Such scheme provides a feasible alternative to the existing injection scheme that could reduce the perturbation during the beam injection during Top-up injection.
Subjects/Keywords: 535
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APA ·
Chicago ·
MLA ·
Vancouver ·
CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Pulampong, T. (2015). Ultra-low emittance lattice design for advanced synchrotron light sources. (Doctoral Dissertation). University of Oxford. Retrieved from http://ora.ox.ac.uk/objects/uuid:092de1c4-f168-4014-a447-778f0c34360c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712059
Chicago Manual of Style (16th Edition):
Pulampong, Thapakron. “Ultra-low emittance lattice design for advanced synchrotron light sources.” 2015. Doctoral Dissertation, University of Oxford. Accessed March 04, 2021.
http://ora.ox.ac.uk/objects/uuid:092de1c4-f168-4014-a447-778f0c34360c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712059.
MLA Handbook (7th Edition):
Pulampong, Thapakron. “Ultra-low emittance lattice design for advanced synchrotron light sources.” 2015. Web. 04 Mar 2021.
Vancouver:
Pulampong T. Ultra-low emittance lattice design for advanced synchrotron light sources. [Internet] [Doctoral dissertation]. University of Oxford; 2015. [cited 2021 Mar 04].
Available from: http://ora.ox.ac.uk/objects/uuid:092de1c4-f168-4014-a447-778f0c34360c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712059.
Council of Science Editors:
Pulampong T. Ultra-low emittance lattice design for advanced synchrotron light sources. [Doctoral Dissertation]. University of Oxford; 2015. Available from: http://ora.ox.ac.uk/objects/uuid:092de1c4-f168-4014-a447-778f0c34360c ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712059
Durham University
12.
Sanders, Scott Edward.
Laser spectroscopy of wire-like molecules.
Degree: PhD, 2012, Durham University
URL: http://etheses.dur.ac.uk/3482/
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549192
► Cavity-enhanced Laser-Induced Fluorescence With the incorporation of a new optic mount and focussing lens a cavity ring-down set-up was altered to collect fluorescence signal from…
(more)
▼ Cavity-enhanced Laser-Induced Fluorescence With the incorporation of a new optic mount and focussing lens a cavity ring-down set-up was altered to collect fluorescence signal from molecules seeded in a molecular beam. Running both the CRDS and fluorescence measurements simultaneously produced a technique with significantly enhanced sensitivity compared to either of the two individual methods. Preliminary analysis with SO2 and a selection of polyaromatic molecules point to the method been best suited for measuring the fluorescence spectra of fast fluorescence lifetime (< 1 ns) molecules and in confined environments i.e. molecular beams. This has been characterised using a known sample and also compared to the CRDS and fluorescence measurements ran as individual techniques. The method was found to increase the sensitivity of the current experimental set-up by two orders of magnitude. This was then applied in the analysis of two new molecular samples to obtain spectra for use in analysing the torsional motions within the molecule. Torsional Motion Analysis of 2,5-bis(phenylethynyl)thiophene Torsional motions in polyphenyls, potential molecular wires, are important in the charge carriage capability of the species. Using a combination of UV-cavity ring-down and fluorescence detection the absorption and photoexcitation spectra of 2,5-bis(phenylethynyl)thiophene were successfully measured. Using a simple cosine potential and simulation program the spectra were reproduced and were found to be close to the values determined in previous research on the two ring system tolane and 1,4-bis(phenylethynyl)benzene.
Subjects/Keywords: 535
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APA ·
Chicago ·
MLA ·
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CSE |
Export
to Zotero / EndNote / Reference
Manager
APA (6th Edition):
Sanders, S. E. (2012). Laser spectroscopy of wire-like molecules. (Doctoral Dissertation). Durham University. Retrieved from http://etheses.dur.ac.uk/3482/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549192
Chicago Manual of Style (16th Edition):
Sanders, Scott Edward. “Laser spectroscopy of wire-like molecules.” 2012. Doctoral Dissertation, Durham University. Accessed March 04, 2021.
http://etheses.dur.ac.uk/3482/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549192.
MLA Handbook (7th Edition):
Sanders, Scott Edward. “Laser spectroscopy of wire-like molecules.” 2012. Web. 04 Mar 2021.
Vancouver:
Sanders SE. Laser spectroscopy of wire-like molecules. [Internet] [Doctoral dissertation]. Durham University; 2012. [cited 2021 Mar 04].
Available from: http://etheses.dur.ac.uk/3482/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549192.
Council of Science Editors:
Sanders SE. Laser spectroscopy of wire-like molecules. [Doctoral Dissertation]. Durham University; 2012. Available from: http://etheses.dur.ac.uk/3482/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.549192
Durham University
13.
Siddons, Paul.
Faraday rotation of pulsed and continuous-wave light in atomic vapour.
Degree: PhD, 2011, Durham University
URL: http://etheses.dur.ac.uk/3218/
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541522
► The absorptive and dispersive properties of a Doppler-broadened vapour of rubidium atoms is investigated. A detailed model of the atom-light interaction is developed and found…
(more)
▼ The absorptive and dispersive properties of a Doppler-broadened vapour of rubidium atoms is investigated. A detailed model of the atom-light interaction is developed and found to be in excellent agreement with experiment in the regime where the interacting light field is sufficiently weak such that it does not significantly alter the medium through which it propagates. The importance of using a weak beam to probe atomic systems is discussed, and a method of characterising how weak such a beam has to be is provided. The theoretical model is applied to both situations of illumination by continuous-wave and pulsed light, the latter situation providing a demonstration of the slow light effect. This phenomenon is a manifestation of the dispersive properties of the medium and is shown to exist over a particularly large frequency range, compared to the absorption spectrum, in thermal vapours. Off-resonant interactions are studied, in which incident laser-light is detuned from resonance to such a degree that Doppler-broadening can be neglected. We quantify the extent to which the light needs to be detuned to be in this regime, and provide approximations to the line-shape function developed in earlier parts of the thesis. The approximate line-shapes are much easier to manipulate and allow a more intuitive understanding of the atom-light interaction. In the second part of the thesis we study the Faraday effect and related phenomena which are an expression of the birefringent properties of the atom-light system. Beginning with a theoretical and experimental investigation of the Faraday rotation of a weak continuous-wave beam, we move on to the consideration of pulsed light. Optically-induced birefringence via the application of an intense continuous-wave pumping field is demonstrated experimentally, and the theoretical plausibility of controlling the polarisation state of a weak pulsed field mediated via intense pulsed light is shown.
Subjects/Keywords: 535
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APA (6th Edition):
Siddons, P. (2011). Faraday rotation of pulsed and continuous-wave light in atomic vapour. (Doctoral Dissertation). Durham University. Retrieved from http://etheses.dur.ac.uk/3218/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541522
Chicago Manual of Style (16th Edition):
Siddons, Paul. “Faraday rotation of pulsed and continuous-wave light in atomic vapour.” 2011. Doctoral Dissertation, Durham University. Accessed March 04, 2021.
http://etheses.dur.ac.uk/3218/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541522.
MLA Handbook (7th Edition):
Siddons, Paul. “Faraday rotation of pulsed and continuous-wave light in atomic vapour.” 2011. Web. 04 Mar 2021.
Vancouver:
Siddons P. Faraday rotation of pulsed and continuous-wave light in atomic vapour. [Internet] [Doctoral dissertation]. Durham University; 2011. [cited 2021 Mar 04].
Available from: http://etheses.dur.ac.uk/3218/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541522.
Council of Science Editors:
Siddons P. Faraday rotation of pulsed and continuous-wave light in atomic vapour. [Doctoral Dissertation]. Durham University; 2011. Available from: http://etheses.dur.ac.uk/3218/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.541522
Durham University
14.
Little, Claire Elspeth.
Computational studies of light-matter interactions in two- and three-dimensional systems.
Degree: PhD, 2011, Durham University
URL: http://etheses.dur.ac.uk/3372/
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545636
► A computational approach is taken to studying a range of light-matter interactions which are interesting in terms of their potential applications as well as from…
(more)
▼ A computational approach is taken to studying a range of light-matter interactions which are interesting in terms of their potential applications as well as from a fundamental point of view. Two different types of polariton, part-light, part-matter quasiparticles, namely exciton-polaritons and Tamm plasmon-polaritons (a type of surface plasmon-polariton) are considered. The conditions required for the strong coupling of optical whispering gallery modes and bulk excitons in submicron spheres are ascertained for the materials gallium arsenide, gallium nitride and zinc oxide. It is shown that the strong coupling regime may be accessed by optical modes with a low decay constant, typically exhibited by those modes with higher angular momentum quantum numbers. Tamm plasmon-polaritons have previously been shown to exist at the boundary between a metal and a planar Bragg reflector structure. The conditions required for the formation of Tamm plasmon-polaritons in cylindrical multilayer structures with a metal core, cladding or metal in both of these locations are determined. The cylindrical Tamm plasmon-polaritons are shown to have low effective masses and low group velocities. It is also shown that it is possible to obtain split polariton modes in structures containing metal in both the core and the cladding. The effect of disorder on a two-dimensional photonic crystal structure consisting of air holes in a slab of dielectric material is studied. It is shown that the defined threshold disorder is not signicantly affected by the dierent relative band widths of the ideal crystal structures considered.
Subjects/Keywords: 535
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APA (6th Edition):
Little, C. E. (2011). Computational studies of light-matter interactions in two- and three-dimensional systems. (Doctoral Dissertation). Durham University. Retrieved from http://etheses.dur.ac.uk/3372/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545636
Chicago Manual of Style (16th Edition):
Little, Claire Elspeth. “Computational studies of light-matter interactions in two- and three-dimensional systems.” 2011. Doctoral Dissertation, Durham University. Accessed March 04, 2021.
http://etheses.dur.ac.uk/3372/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545636.
MLA Handbook (7th Edition):
Little, Claire Elspeth. “Computational studies of light-matter interactions in two- and three-dimensional systems.” 2011. Web. 04 Mar 2021.
Vancouver:
Little CE. Computational studies of light-matter interactions in two- and three-dimensional systems. [Internet] [Doctoral dissertation]. Durham University; 2011. [cited 2021 Mar 04].
Available from: http://etheses.dur.ac.uk/3372/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545636.
Council of Science Editors:
Little CE. Computational studies of light-matter interactions in two- and three-dimensional systems. [Doctoral Dissertation]. Durham University; 2011. Available from: http://etheses.dur.ac.uk/3372/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545636
15.
Lei, Dang-Yuan.
Superfocusing, biosensing and modulation in plasmonics.
Degree: PhD, 2011, Imperial College London
URL: http://hdl.handle.net/10044/1/9046
► Plasmonics could bridge the gap between photonics and electronics at the nanoscale, by allowing the realization of surface-plasmon-based circuits and plasmonic chips in the future.…
(more)
▼ Plasmonics could bridge the gap between photonics and electronics at the nanoscale, by allowing the realization of surface-plasmon-based circuits and plasmonic chips in the future. To build up such devices, elementary components are required, such as a passive plasmonic lens to focus free-space light to nanometre area and an active plasmonic modulator or switch to control an optical response with an external signal (optical, thermal or electrical). This thesis partially focuses on designing novel passive and active plasmonic devices, with a specific emphasis on the understanding of the physical principles lying behind these nanoscale optical phenomena. Three passive plasmonic devices, designed by conformal transformation optics, are numerically studied, including nanocrescents, kissing and overlapping nanowire dimers. Contrary to conventional metal nanoparticles with just a few resonances, these devices with structural singularities are able to harvest light over a broadband spectrum and focus it into well-defined positions, with potential applications in high efficiency solar cells and nanowire-based photodetectors and nanolasers. Moreover, thermo-optical and electrooptical modulation of plasmon resonances are realized in metallic nanostructures integrated with either a temperature-controlled phase transition material (vanadium dioxide, VO2), or ferroelectric thin films. Taking advantage of the high sensitivity of particle plasmon resonances to the change of its surrounding environment, we develop a plasmon resonance nanospectroscopy technique to study the effects of sizes and defects in the metal-insulator phase transition of VO2 at the single-particle level, and even single-domain level. Finally, we propose and examine the use of two-dimensional metallic nanohole arrays as a refractive index sensing platform for future label-free biosensors with good surface sensitivity and high-throughput detection ability. The designed plasmonic devices have great potential implications for constructing nextgeneration optical computers and chip-scale biosensors. The developed plasmon resonance nanospectroscopy has the potential to probe the interfacial or domain boundary scattering in polycrystalline and epitaxial thin films.
Subjects/Keywords: 535
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APA (6th Edition):
Lei, D. (2011). Superfocusing, biosensing and modulation in plasmonics. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/9046
Chicago Manual of Style (16th Edition):
Lei, Dang-Yuan. “Superfocusing, biosensing and modulation in plasmonics.” 2011. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/9046.
MLA Handbook (7th Edition):
Lei, Dang-Yuan. “Superfocusing, biosensing and modulation in plasmonics.” 2011. Web. 04 Mar 2021.
Vancouver:
Lei D. Superfocusing, biosensing and modulation in plasmonics. [Internet] [Doctoral dissertation]. Imperial College London; 2011. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/9046.
Council of Science Editors:
Lei D. Superfocusing, biosensing and modulation in plasmonics. [Doctoral Dissertation]. Imperial College London; 2011. Available from: http://hdl.handle.net/10044/1/9046
16.
Bissell, John Joseph.
Magnetised transport and instability in laser produced plasmas.
Degree: PhD, 2012, Imperial College London
URL: http://hdl.handle.net/10044/1/9176
► Classical transport theory predicts strong coupling between thermal transport and magnetic field dynamics in laser produced plasmas; for example, fields are carried with the thermal…
(more)
▼ Classical transport theory predicts strong coupling between thermal transport and magnetic field dynamics in laser produced plasmas; for example, fields are carried with the thermal flux, via the Nernst effect, while simultaneously deflecting it, giving rise to a Righi-Leduc heat-flow. Coupling between these effects is shown here to drive a new kind of instability-the magnetothermal instability-which is described in detail for the first time. A linear perturbation theory is derived in the absence of density gradients and hydrodynamical effects, and yields unstable solutions which propagate as magnetothermal waves. The theory is compared with full non-linear simulation in the context of a recent nanosecond gas-jet experiment and found to be in good agreement; exhibiting typical growth-rates and characteristic wavelengths of order 10ns-1 and 50µ m respectively. Further incorporation of density gradients and hydrodynamics into the magnetothermal stability analysis is shown to introduce the well-known field generating thermal instability source term, which can either complement or counteract the magnetothermal mechanism. Inequalities for predicting the dominance of each process are given: of the two, the magnetothermal mechanism is found to represent the main-and sometimes only-source of unstable feedback for the conditions considered here. Using super-Gaussian transport theory, the implications of inverse-bremmstrahlung heating for transport in laser-plasmas are also explored. Super-Gaussian modifications are shown to suppress a number of classical processes, by up to ~90% in some cases, while simultaneously introducing new effects, such as advection of magnetic field up density gradients. The combined consequences of these modifications are considered for the field generating thermal instability, and super-Gaussian effects are found to reduce growthrates by [greater than or similar to] 80% compared to predictions from classical transport theory under inertial confinement fusion conditions. The development of a unique code CTC, written to assist the exploration of both classical and super-Gaussian transport phenomena, and the new magnetothermal instability, is also described.
Subjects/Keywords: 535
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APA (6th Edition):
Bissell, J. J. (2012). Magnetised transport and instability in laser produced plasmas. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/9176
Chicago Manual of Style (16th Edition):
Bissell, John Joseph. “Magnetised transport and instability in laser produced plasmas.” 2012. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/9176.
MLA Handbook (7th Edition):
Bissell, John Joseph. “Magnetised transport and instability in laser produced plasmas.” 2012. Web. 04 Mar 2021.
Vancouver:
Bissell JJ. Magnetised transport and instability in laser produced plasmas. [Internet] [Doctoral dissertation]. Imperial College London; 2012. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/9176.
Council of Science Editors:
Bissell JJ. Magnetised transport and instability in laser produced plasmas. [Doctoral Dissertation]. Imperial College London; 2012. Available from: http://hdl.handle.net/10044/1/9176
17.
Frank, Felix.
Generation and application of ultrashort laser pulses in attosecond science.
Degree: PhD, 2011, Imperial College London
URL: http://hdl.handle.net/10044/1/7025
► In this thesis, I describe the development of a sub-4 fs few-cycle laser system at Imperial College London used to generate and characterise the first…
(more)
▼ In this thesis, I describe the development of a sub-4 fs few-cycle laser system at Imperial College London used to generate and characterise the first single attosecond (1 as = 10-18s) pulses in the UK. Phase-stabilised few-cycle laser pulses were generated using a hollow fibre system with a chirped mirror compression setup. The pulse was fully characterised using frequency-resolved optical gating (FROG) and spectral phase interferometry for direct electric field reconstruction in a spatially encoded filter arrangement (SEA-F-SPIDER). A pulse duration of 3.5 fs was measured with an argon filled hollow fibre. These phase stabilised Infra-Red (IR) pulses were used to generate a continuous spectrum of high harmonics in the Extreme Ultraviolet (XUV) originating from a single half-cycle of the driving field. Using subsequent spectral filtering, a single attosecond pulse was generated. The isolated XUV pulse was characterised using an atomic streaking camera and a pulse duration of ~260 as was retrieved using FROG for complete reconstruction of attosecond bursts (FROG-CRAB). In an experiment conducted at the Rutherford Appleton Laboratory, high harmonics were generated using a two-colour field with an energetic beam at 1300nm and a weak second harmonic orthogonally polarized to the fundamental. By changing the phase between the two fields, a deep modulation of the harmonic yield is seen and an enhancement of one order of magnitude compared to the single colour field with the same energy is observed.
Subjects/Keywords: 535
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APA (6th Edition):
Frank, F. (2011). Generation and application of ultrashort laser pulses in attosecond science. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/7025
Chicago Manual of Style (16th Edition):
Frank, Felix. “Generation and application of ultrashort laser pulses in attosecond science.” 2011. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/7025.
MLA Handbook (7th Edition):
Frank, Felix. “Generation and application of ultrashort laser pulses in attosecond science.” 2011. Web. 04 Mar 2021.
Vancouver:
Frank F. Generation and application of ultrashort laser pulses in attosecond science. [Internet] [Doctoral dissertation]. Imperial College London; 2011. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/7025.
Council of Science Editors:
Frank F. Generation and application of ultrashort laser pulses in attosecond science. [Doctoral Dissertation]. Imperial College London; 2011. Available from: http://hdl.handle.net/10044/1/7025
18.
Brugnera, Leonardo.
Control of high harmonic generation by manipulation of field parameters.
Degree: PhD, 2011, Imperial College London
URL: http://hdl.handle.net/10044/1/9151
► ?High harmonic generation is a well established technique to investigate the structure and the inner dynamics of atoms and molecules. This thesis describes how the…
(more)
▼ ?High harmonic generation is a well established technique to investigate the structure and the inner dynamics of atoms and molecules. This thesis describes how the generating field parameters can be manipulated to extend the limits imposed on the technique by the use of traditional laser sources. In this field, with traditional source we mean high intensity, linearly polarised laser pulses at 800 nm. The first parameter to be investigated is the wavelength λ of the generating beam. The unfavourable scaling of the high harmonic yield with λ seems to suggest that high harmonic spectroscopy of atoms and molecules should be restricted to the wavelengths that obviate this problem, and that therefore shorter wavelength should be used. But longer wavelengths, in the mid infrared, present a great advantage respect to shorter ones. The maximum harmonic order that we can obtain is proportional to the ionisation potential of the target and to the wavelength times the intensity of the beam, so a higher number of harmonic can be produced with a longer wavelength than with short, the intensity being equal. This becomes incredibly valuable when the specie under investigation is a molecule with low ionisation potential. To produce high harmonics, a linearly polarised beam is required. If ellipticity is introduced in the beam, the harmonic signal quickly fades out, as non-linearly polarisation in monochromatic beams switches off the mechanism at the basis of high harmonic generation. This is not true if the polarisation of the beam is changed through the introduction of an additional laser beam, perpendicularly polarised respect to the fundamental. In this thesis the additional degree of freedom that this second field implies is investigated by combining the fundamental with its second harmonic and by controlling the relative delay of the two with sub-cycle precision. The key result is that the addition of the second harmonic gives access to the control of the harmonic amplitude and to the time at which the high harmonics are emitted, by simply controlling the relative phase between the two pulses.
Subjects/Keywords: 535
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APA (6th Edition):
Brugnera, L. (2011). Control of high harmonic generation by manipulation of field parameters. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/9151
Chicago Manual of Style (16th Edition):
Brugnera, Leonardo. “Control of high harmonic generation by manipulation of field parameters.” 2011. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/9151.
MLA Handbook (7th Edition):
Brugnera, Leonardo. “Control of high harmonic generation by manipulation of field parameters.” 2011. Web. 04 Mar 2021.
Vancouver:
Brugnera L. Control of high harmonic generation by manipulation of field parameters. [Internet] [Doctoral dissertation]. Imperial College London; 2011. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/9151.
Council of Science Editors:
Brugnera L. Control of high harmonic generation by manipulation of field parameters. [Doctoral Dissertation]. Imperial College London; 2011. Available from: http://hdl.handle.net/10044/1/9151
19.
Bharadia, Shailen.
Towards laser spectroscopy of highly charged ions : dynamics of 40Ca+ ions in a Penning trap.
Degree: PhD, 2011, Imperial College London
URL: http://hdl.handle.net/10044/1/9138
► To date, the most successful quantum field theory is quantum electrodynamics (QED) which offers a fully quantum mechanical description of the electromagnetic interaction between charged…
(more)
▼ To date, the most successful quantum field theory is quantum electrodynamics (QED) which offers a fully quantum mechanical description of the electromagnetic interaction between charged particles. Laboratory tests of the theory have been performed for a wide range of field strengths and no significant deviation from the predictions of the theory have been found. For heavy highly charged ions (HCI), the electric and magnetic fields around the nucleus can be orders of magnitude higher than those achievable by conventional means in a laboratory. Therefore, these ions offer a new regime in which the theory should be tested. For HCI above Z > 60, the ground state hyper fine structure splitting (HFS) shifts into the optical region, and becomes accessible to laser light sources. The aim of the SPECTRAP experiment at GSI in Germany, is to perform laser spectroscopy of the HFS in H-like and Li-like HCI, as a test of the corresponding bound-state QED calculations. In order for this to be successful, the weak magnetic HFS transitions need to be measured to a high precision. This will be accomplished in the SPECTRAP experiment by trapping and cooling bunches of HCI, such that the relative precision of the measured transition will be on the level of 10-7, allowing bound-state high order QED calculations to be tested to the level of a few percent. As fluorescence rates will be low, a critical final part in preparing the ions in the trap will be the application of a rotating dipole ('rotating wall') about the magnetic field axis allowing for compression of the ion cloud in the trap, thereby increasing the fluorescence collection efficiency and signal to noise for detection. In London, due to the availability of our own superconducting magnet, we have performed systematic measurements of the dynamics of laser cooled Ca+ ions confined in a Penning trap driven by a rotating wall. With CCD camera imaging, we have measured the fluorescence from a cloud of ions, identified as being a strongly correlated non-neutral plasma, as a function of the rotating wall drive amplitude, frequency, sense of rotation and trap potential. We show that a cloud driven at sufficient amplitude reaches a low-slip regime within the time frame of a single CCD exposure (~ 1s), and that heating resonances are observed on scanning the rotation frequency. These resonances are identified as being associated with the axial motion of the ions in the trap potential, and the lowest order azimuthal plasma modes which are believed to be excited indirectly by a misalignment of the electric and magnetic fields. By operating the rotating wall in the opposite sense of rotation to that used for cloud compression, the excitation of these plasma modes is shown to be a good diagnostic probe of the laser cooled rigid rotation frequency of the cloud, allowing the number density to be inferred from the measurement. These results will allow the SPECTRAP collaboration to define a procedure and set of optimum parameters for use of the rotating wall technique that offers maximum…
Subjects/Keywords: 535
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MLA ·
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APA (6th Edition):
Bharadia, S. (2011). Towards laser spectroscopy of highly charged ions : dynamics of 40Ca+ ions in a Penning trap. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/9138
Chicago Manual of Style (16th Edition):
Bharadia, Shailen. “Towards laser spectroscopy of highly charged ions : dynamics of 40Ca+ ions in a Penning trap.” 2011. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/9138.
MLA Handbook (7th Edition):
Bharadia, Shailen. “Towards laser spectroscopy of highly charged ions : dynamics of 40Ca+ ions in a Penning trap.” 2011. Web. 04 Mar 2021.
Vancouver:
Bharadia S. Towards laser spectroscopy of highly charged ions : dynamics of 40Ca+ ions in a Penning trap. [Internet] [Doctoral dissertation]. Imperial College London; 2011. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/9138.
Council of Science Editors:
Bharadia S. Towards laser spectroscopy of highly charged ions : dynamics of 40Ca+ ions in a Penning trap. [Doctoral Dissertation]. Imperial College London; 2011. Available from: http://hdl.handle.net/10044/1/9138
20.
Iles-Smith, Jake.
Excitation dynamics of strongly dissipative quantum systems.
Degree: PhD, 2015, Imperial College London
URL: http://hdl.handle.net/10044/1/33203
► Strong coupling between a quantum system and its many-body environment is becoming an increasingly important topic for many branches of physics. Numerous systems of experimental…
(more)
▼ Strong coupling between a quantum system and its many-body environment is becoming an increasingly important topic for many branches of physics. Numerous systems of experimental and technological relevance demonstrate strong system-environment coupling, leading to complex dynamical behaviour. This thesis is concerned with two particular examples of such systems, namely quantum dots (QDs) and excitonic energy transfer (EET) in molecular systems. Traditional quantum optics treatments are often insufficient to describe the transient, steady state, and optical properties of QDs due to system-environment correlations. In contrast, we present a modified theory of quantum optics capable of capturing the influence of a thermal environment on the behaviour of QDs. Using this framework we demonstrate a striking departure of the emission spectra and photon measurement statistics of a classically driven QD when compared to an analogous atomic system. Furthermore, in contradiction to accepted notions of decoherence and dissipation, we show that the interaction between a QD and its thermal environment induces non-classical light-matter correlations in an otherwise semi-classical regime of cavity quantum electrodynamics. Away from QDs, we develop the reaction coordinate (RC) formalism to describe the dynamics of a system coupled to a low frequency environment - a regime important to EET systems. We do so by identifying and incorporating important environmental degrees of freedom into an enlarged system Hamiltonian. Uniquely, this approach gives insight directly into the dynamical evolution of the environment and correlations accumulated between the system and environment. Furthermore, it is demonstrated that these corre- lations persist into the steady state, generating non-canonical equilibrium states of the system and environment. We then apply the RC model to describe EET in a molecular dimer, highlighting the effect that under- and over-damped environments have on the excitation dynamics. In doing so, we show interactions between the dimer and a structured environment can significantly enhance the energy transfer rate.
Subjects/Keywords: 535
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APA (6th Edition):
Iles-Smith, J. (2015). Excitation dynamics of strongly dissipative quantum systems. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/33203
Chicago Manual of Style (16th Edition):
Iles-Smith, Jake. “Excitation dynamics of strongly dissipative quantum systems.” 2015. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/33203.
MLA Handbook (7th Edition):
Iles-Smith, Jake. “Excitation dynamics of strongly dissipative quantum systems.” 2015. Web. 04 Mar 2021.
Vancouver:
Iles-Smith J. Excitation dynamics of strongly dissipative quantum systems. [Internet] [Doctoral dissertation]. Imperial College London; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/33203.
Council of Science Editors:
Iles-Smith J. Excitation dynamics of strongly dissipative quantum systems. [Doctoral Dissertation]. Imperial College London; 2015. Available from: http://hdl.handle.net/10044/1/33203
Cranfield University
21.
Topliss, Stephen M.
Optical fibre long period grating sensors with nanostructured coatings.
Degree: PhD, 2011, Cranfield University
URL: http://dspace.lib.cranfield.ac.uk/handle/1826/6799
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542230
► The dual resonant response of long period fibre gratings (LPG) operating near the phase matching turning point to the deposition of nanostructured coatings is explored.…
(more)
▼ The dual resonant response of long period fibre gratings (LPG) operating near the phase matching turning point to the deposition of nanostructured coatings is explored. A broad range of LPGs have been fabricated with grating periods ranging from 80m to 180m, and these have been characterized with three different coating materials,-tricosensoic acid, undecyl-calix[4]resorcarene and tert-butyl-calix[8]arene carboxylic acid. The dual resonant response has been exploited with the construction of an LPG based sensor coated with a quinolinium dye forming a pH sensor. The wavelength response of this device was measured with a sensitivity of -0.55pH/nm. Furthermore, length apodised phase shifted long period gratings have been characterized, and the effect on the dual resonant response has been recorded. Partial coating of this device has resulted in the observation of a bandgap feature in the wavelength response. The use of calixarenes as a functional coating for long period fibre gratings is also investigated. Calixarene is applied in a thin layer with a thickness of several hundred nm’s to the cladding of the fibre in the region containing the LPG sensor. The chemical sensing capabilities of a long period fibre grating sensor is presented for the detection of the volatile organic compounds; hexane, cyclohexane, benzene and toluene. The wavelength response was measured and the sensitivity to toluene vapour was recorded at 1600ppmv/nm. Using intensity detection of the central maxima in the wavelength response, the chemical selectivity is demonstrated showing sensitivity to toluene vapour over 13 times greater compared to hexane vapour.
Subjects/Keywords: 535
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APA (6th Edition):
Topliss, S. M. (2011). Optical fibre long period grating sensors with nanostructured coatings. (Doctoral Dissertation). Cranfield University. Retrieved from http://dspace.lib.cranfield.ac.uk/handle/1826/6799 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542230
Chicago Manual of Style (16th Edition):
Topliss, Stephen M. “Optical fibre long period grating sensors with nanostructured coatings.” 2011. Doctoral Dissertation, Cranfield University. Accessed March 04, 2021.
http://dspace.lib.cranfield.ac.uk/handle/1826/6799 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542230.
MLA Handbook (7th Edition):
Topliss, Stephen M. “Optical fibre long period grating sensors with nanostructured coatings.” 2011. Web. 04 Mar 2021.
Vancouver:
Topliss SM. Optical fibre long period grating sensors with nanostructured coatings. [Internet] [Doctoral dissertation]. Cranfield University; 2011. [cited 2021 Mar 04].
Available from: http://dspace.lib.cranfield.ac.uk/handle/1826/6799 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542230.
Council of Science Editors:
Topliss SM. Optical fibre long period grating sensors with nanostructured coatings. [Doctoral Dissertation]. Cranfield University; 2011. Available from: http://dspace.lib.cranfield.ac.uk/handle/1826/6799 ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.542230
University of York
22.
Hobbs, Lauren.
Extreme ultraviolet probing of laser ablation.
Degree: PhD, 2011, University of York
URL: http://etheses.whiterose.ac.uk/1605/
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538653
► This thesis details the use of extreme ultraviolet (EUV) sources in probing laser ablation and material opacity. The radiation hydrodynamic codes POLLUX and h2d are…
(more)
▼ This thesis details the use of extreme ultraviolet (EUV) sources in probing laser ablation and material opacity. The radiation hydrodynamic codes POLLUX and h2d are used to study the Rayleigh-Taylor instability in a regime relevant to inertial fusion energy and, in support of experimental effort, to test the feasibility of methods for measurement of iron opacity. Simulations of EUV radiography using the POLLUX code show how the presence of warm, dense material leads to strong absorption of the probe beam. Methods using both broad and narrowband EUV wavelength probes for benchmarking theoretical models of opacity are presented. An iron opacity experiment conducted at the Bhabha Atomic Research Centre is modelled, where K_alpha emission from an aluminium layer is used to probe an iron layer beneath. H2d simulations of laser heated iron, conducted to determine the suitability of experimental results obtained at the Rutherford Appleton Laboratory for iron opacity, show the difficulty in preventing large temperature and density gradients from forming. Interferometry has been used to measure both transmission and phase information for a 21.2 nm zinc EUV laser beam probing longitudinally through laser ablated CH plastic at the Prague Asterix Laser System. By conducting interferometric probing with EUV laser light, the region of warm dense matter between the critical surface and ablation surface in a laser ablated plasma is diagnosed. Analysis of phase shifts reveals refractive indices below solid and plasma values arising in CH plastic, due to bound-free absorption in C+, a model for which is presented. The transmission of the EUV probe beam provides a measure of the rate of ablation, matching previous experimental scaling laws.
Subjects/Keywords: 535
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APA (6th Edition):
Hobbs, L. (2011). Extreme ultraviolet probing of laser ablation. (Doctoral Dissertation). University of York. Retrieved from http://etheses.whiterose.ac.uk/1605/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538653
Chicago Manual of Style (16th Edition):
Hobbs, Lauren. “Extreme ultraviolet probing of laser ablation.” 2011. Doctoral Dissertation, University of York. Accessed March 04, 2021.
http://etheses.whiterose.ac.uk/1605/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538653.
MLA Handbook (7th Edition):
Hobbs, Lauren. “Extreme ultraviolet probing of laser ablation.” 2011. Web. 04 Mar 2021.
Vancouver:
Hobbs L. Extreme ultraviolet probing of laser ablation. [Internet] [Doctoral dissertation]. University of York; 2011. [cited 2021 Mar 04].
Available from: http://etheses.whiterose.ac.uk/1605/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538653.
Council of Science Editors:
Hobbs L. Extreme ultraviolet probing of laser ablation. [Doctoral Dissertation]. University of York; 2011. Available from: http://etheses.whiterose.ac.uk/1605/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538653
University of Manchester
23.
Sutherland, Danny.
Optical characterisation of non-polar InGaN/GaN quantum wells.
Degree: PhD, 2015, University of Manchester
URL: https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-nonpolar-ingangan-quantum-wells(34ce6283-262b-491e-ad3d-3e2ab95cb434).html
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677786
► In this thesis I present research on the optical characterisation of InGaN/GaN quantum wells (QWs) grown in the non-polar the a-plane (11-20) and m-plane (1-100)…
(more)
▼ In this thesis I present research on the optical characterisation of InGaN/GaN quantum wells (QWs) grown in the non-polar the a-plane (11-20) and m-plane (1-100) orientations. The research is performed using optical techniques such as photoluminescence (PL), photoluminescence excitation (PLE), time-resolved photoluminescence (TRPL) and photoluminescence decay time studies. Additionally comparisons are drawn to structural details provided by the University of Cambridge. In the first section I investigate and compare various defect reduction techniques that are utilised in the growth of a-plane GaN on r-plane sapphire. These are included as a way of reducing the density of basal-plane stacking faults (BSFs) and threading dislocations (TDs). I will show that a comparison between the integrated emission intensity of the donor-bound exciton against that of the BSFs and the TDs can be used as a means of comparing the relative crystal quality of different samples. I will also show that techniques which employ a physical layer to block BSFs and TDs from propagating are the most effective in reducing their densities for a-plane GaN grown on r-plane sapphire. In the second section I discuss the characterisation of m-plane InGaN/GaN QWs, focusing primarily on the presence of an extended low energy emission tail. Through the use of decay time studies and TRPL I am able to show that the extended low energy emission tail originates from semi-polar QWs which form during growth. Additionally I show that over the majority of the emission band, the PL decay time possesses a single time constant that does not vary significantly with detection energy. This observation is consistent with the recombination of localised excitons in the m-plane InGaN/GaN QWs. For the final section I compare InGaN/GaN QWs grown on the a-plane and the m-plane for the purpose of understanding why m-plane samples typically exhibit superior optical properties. In this section I identify an additional emission band that exists on the high energy side of the QW emission and is comparably stronger in the a-plane samples. This emission band is responsible for the difference in the PL decay times observed between each non-polar growth orientation, as well for as the reduction in the degree of linear polarisation measured for a-plane QW samples.
Subjects/Keywords: 535
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APA (6th Edition):
Sutherland, D. (2015). Optical characterisation of non-polar InGaN/GaN quantum wells. (Doctoral Dissertation). University of Manchester. Retrieved from https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-nonpolar-ingangan-quantum-wells(34ce6283-262b-491e-ad3d-3e2ab95cb434).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677786
Chicago Manual of Style (16th Edition):
Sutherland, Danny. “Optical characterisation of non-polar InGaN/GaN quantum wells.” 2015. Doctoral Dissertation, University of Manchester. Accessed March 04, 2021.
https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-nonpolar-ingangan-quantum-wells(34ce6283-262b-491e-ad3d-3e2ab95cb434).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677786.
MLA Handbook (7th Edition):
Sutherland, Danny. “Optical characterisation of non-polar InGaN/GaN quantum wells.” 2015. Web. 04 Mar 2021.
Vancouver:
Sutherland D. Optical characterisation of non-polar InGaN/GaN quantum wells. [Internet] [Doctoral dissertation]. University of Manchester; 2015. [cited 2021 Mar 04].
Available from: https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-nonpolar-ingangan-quantum-wells(34ce6283-262b-491e-ad3d-3e2ab95cb434).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677786.
Council of Science Editors:
Sutherland D. Optical characterisation of non-polar InGaN/GaN quantum wells. [Doctoral Dissertation]. University of Manchester; 2015. Available from: https://www.research.manchester.ac.uk/portal/en/theses/optical-characterisation-of-nonpolar-ingangan-quantum-wells(34ce6283-262b-491e-ad3d-3e2ab95cb434).html ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.677786
University of Leeds
24.
Blake, Tony.
A quantum approach to cavity mediated laser cooling.
Degree: PhD, 2011, University of Leeds
URL: http://etheses.whiterose.ac.uk/2167/
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547535
► Cavity-mediated cooling has the potential to become one of the most efficient techniques to cool molecular species down to very low temperatures. This thesis studies…
(more)
▼ Cavity-mediated cooling has the potential to become one of the most efficient techniques to cool molecular species down to very low temperatures. This thesis studies the use of rate equations to analyse the cooling process in such systems. In particular the master equation is used to find rate equations that can determine the rate of change of phonons in the system. The general idea behind cavity cooling is the continuous conversion of phonons into cavity photons. While there is no spontaneous emission and decay rate associated with the concept of phonons, photons are created after a change in the phonon number has occurred and can then leak out through the cavity mirrors easily. Hence the conversion of phonons into photons can result in the constant removal of phonon energy from the system. In this thesis we compare cavity mediated cooling with single particle laser cooling. It is shown that cavity cooling is essentially the same as ordinary laser cooling. This is done by calculating the stationary state phonon number mss and the cooling rate y as a function of the system parameters. For example, when the trap phonon frequency υ is either much larger or much smaller than the cavity decay rate k , the minimum stationary state phonon number scales as k²/16v² (strong confinement regime) and as k/4 (weak confinement regime), respectively. Replacing k with Ѓ yields the steady states associated with ordinary laser cooling.
Subjects/Keywords: 535
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APA (6th Edition):
Blake, T. (2011). A quantum approach to cavity mediated laser cooling. (Doctoral Dissertation). University of Leeds. Retrieved from http://etheses.whiterose.ac.uk/2167/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547535
Chicago Manual of Style (16th Edition):
Blake, Tony. “A quantum approach to cavity mediated laser cooling.” 2011. Doctoral Dissertation, University of Leeds. Accessed March 04, 2021.
http://etheses.whiterose.ac.uk/2167/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547535.
MLA Handbook (7th Edition):
Blake, Tony. “A quantum approach to cavity mediated laser cooling.” 2011. Web. 04 Mar 2021.
Vancouver:
Blake T. A quantum approach to cavity mediated laser cooling. [Internet] [Doctoral dissertation]. University of Leeds; 2011. [cited 2021 Mar 04].
Available from: http://etheses.whiterose.ac.uk/2167/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547535.
Council of Science Editors:
Blake T. A quantum approach to cavity mediated laser cooling. [Doctoral Dissertation]. University of Leeds; 2011. Available from: http://etheses.whiterose.ac.uk/2167/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.547535
25.
Hawkins, Peter.
High harmonic generation in periodic systems.
Degree: PhD, 2016, Imperial College London
URL: http://hdl.handle.net/10044/1/43375
► In this thesis theoretical models for describing ultrafast dynamics and High Harmonic Generation (HHG) in bulk periodic systems are developed. HHG in bulk solid state…
(more)
▼ In this thesis theoretical models for describing ultrafast dynamics and High Harmonic Generation (HHG) in bulk periodic systems are developed. HHG in bulk solid state systems has been achieved by several groups over the last few years. In this thesis a review of recent results is presented, with attention paid to the development of theoretical models for the HHG process in periodic solids. A closed form expression for a Landau-Dykhne type sub-cycle transition rate between bands of nearest-neighbour tight-binding structures is derived. This rate is used to construct a semi-classical model for HHG in solids. The sub-cycle nature of the transition rate is shown to lead to destructive interference of currents in the conduction band. The time dependent Schödinger equation is employed in the accelerated Bloch basis to study the effect of multiple bands on the HHG process. For mid-IR fields transitions between bands can be sufficiently strong that transitions between the conduction bands suppress the Bragg reflection process. It is shown that such transitions can form an effective nearly parabolic conduction band, and lead to a large reduction in harmonic intensity compared to single conduction band models. The prediction of destructive interference of current in the conduction band of periodic solids is studied in ZnO, using a non-local empirical pseudopotential band structure and matrix elements, in the density matrix formalism, with the inclusion of dephasing effects. It is shown that the quantum destructive interference is present in the density matrix calculation, closely matching semi-classical predictions. The effect of multiple bands of the structure, and variation in the dephasing timescale of the system is also considered.
Subjects/Keywords: 535
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APA (6th Edition):
Hawkins, P. (2016). High harmonic generation in periodic systems. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/43375
Chicago Manual of Style (16th Edition):
Hawkins, Peter. “High harmonic generation in periodic systems.” 2016. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/43375.
MLA Handbook (7th Edition):
Hawkins, Peter. “High harmonic generation in periodic systems.” 2016. Web. 04 Mar 2021.
Vancouver:
Hawkins P. High harmonic generation in periodic systems. [Internet] [Doctoral dissertation]. Imperial College London; 2016. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/43375.
Council of Science Editors:
Hawkins P. High harmonic generation in periodic systems. [Doctoral Dissertation]. Imperial College London; 2016. Available from: http://hdl.handle.net/10044/1/43375
26.
Thomas, Gabrielle Marie.
High power modelocking using a nonlinear mirror.
Degree: PhD, 2012, Imperial College London
URL: http://hdl.handle.net/10044/1/9185
► This thesis presents work on the high average power operation of pulsed diode-pumped solid-state lasers by using a laser configuration known as the bounce geometry.…
(more)
▼ This thesis presents work on the high average power operation of pulsed diode-pumped solid-state lasers by using a laser configuration known as the bounce geometry. The bounce geometry has previously produced efficient, high power and high spatial quality laser outputs in continuous-wave, Q-switched and modelocked regimes. This thesis explores the capabilities of the bounce geometry for power scaling, shown using Nd:YVO4 and Nd:GdVO4 in both a passively Q-switched laser system and a variety of nonlinear mirror modelocked systems. The high gain experienced by Nd-doped gain media pumped at 808 nm has traditionally posed difficulties in producing stable passive Q-switching with Cr4+:YAG. By using a novel stigmatic design of the bounce geometry that experiences lower gain, but highly circular output, passive Q-switching with > 11 W of average power is produced, at a pulse repetition rate of 190 kHz. This is the highest output power ever achieved from a passively Q-switched Nd-doped vanadate laser to date. Nonlinear mirror modelocking is a passive modelocking technique that employs a χ(2) nonlinear medium in combination with a dichroic output coupler. The first nonlinear mirror modelocking of a bounce geometry laser is presented, obtaining 11.3 W of average power and 57 ps pulse duration using a type-II phase-matched KTP nonlinear crystal. Using type-I phase-matched BiBO, shorter pulses of 5.7 ps in duration are obtained at an average power of 6.1 W. The nonlinear mirror modelocking technique is then applied to the stigmatic bounce geometry laser, obtaining a highly stable train of modelocked pulses with pulse duration 14 ps and an average power of 12 W, with high spatial quality output. Mixed vanadate lasers offer customisation of the laser fluorescence spectrum, but tend to experience lower gain than single vanadates. Using the mixed vanadate combination Nd:Gd0.6Y0.4YVO4 in the bounce geometry, 27.5 W of average power in continuous-wave operation is shown. This is the highest power of any mixed vanadate laser ever reported. By then applying the nonlinear mirror modelocking technique to the mixed vanadate system, 16.8 W of average modelocked output power and a pulse duration of 12.7 ps is obtained. This is simultaneously the first time that the nonlinear mirror technique has been applied to mixed vanadate gain media and the highest power of any modelocked mixed vanadate laser to date. Finally, power scaling of a nonlinear mirror modelocked Nd:GdVO4 laser in the bounce geometry is achieved through use of the double bounce geometry design and through use of a high power pump diode. The system employing the high power pumping produced > 30 W of average power — world record power using the nonlinear mirror technique.
Subjects/Keywords: 535
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APA (6th Edition):
Thomas, G. M. (2012). High power modelocking using a nonlinear mirror. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/9185
Chicago Manual of Style (16th Edition):
Thomas, Gabrielle Marie. “High power modelocking using a nonlinear mirror.” 2012. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/9185.
MLA Handbook (7th Edition):
Thomas, Gabrielle Marie. “High power modelocking using a nonlinear mirror.” 2012. Web. 04 Mar 2021.
Vancouver:
Thomas GM. High power modelocking using a nonlinear mirror. [Internet] [Doctoral dissertation]. Imperial College London; 2012. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/9185.
Council of Science Editors:
Thomas GM. High power modelocking using a nonlinear mirror. [Doctoral Dissertation]. Imperial College London; 2012. Available from: http://hdl.handle.net/10044/1/9185
27.
Chaudhary, Mohammad Yaqub.
Charge transport, injection and optical properties of fluorene based copolymers.
Degree: PhD, 2015, Imperial College London
URL: http://hdl.handle.net/10044/1/33205
► In this work we investigate the charge transport, injection and optical properties of several series of fluorene based copolymers. These properties are key areas for…
(more)
▼ In this work we investigate the charge transport, injection and optical properties of several series of fluorene based copolymers. These properties are key areas for polymer semiconductor research studies that are intended to address the challenges of achieving electrically pumped polymer lasing. In general, high charge carrier mobility and luminescence efficiency have been found to be mutually exclusive, however, optimising both together, as well as demonstrating high optical gain will be a significant step to offset losses associated with the mechanisms for lasing. A further requirement is that it is necessary to achieve efficient charge injection in the particular materials that are found to have both of these properties optimised. We concentrate our investigation on fluorene-based copolymers, which have been amongst the earliest classes of materials of interest for polymer lasers (including studies in optically pumped polymer lasers), and since it has previously been shown that high hole mobility and luminescence efficiency may be achieved in fluorene based copolymers with simple alterations to side chain configurations. However, ohmic hole injection into poly(9,9-dioctylfluorene) (PFO) has been difficult to achieve because of its deep-lying highest occupied molecular orbital (HOMO) level of ~5.8eV below the vacuum level. Therefore, in our first experimental study, we revisit the charge transport properties of PFO based on recent developments in the use of transition metal oxides as hole injecting electrodes. With the ability to achieve ohmic injection in PFO, we are able to use Dark Injection Space Charge Limited Current (DI-SCLC) and field effect transistor (FET) techniques, both of which require ohmic injecton for charge transport measurements, and make comparisons with measurements from Time-of-Flight (ToF) photocurrent experiments. Together, these techniques span several orders of magnitude in charge carrier density, which provides an additional perspective on charge transport and the presence of charge traps. The subsequent chapters introduce three series of fluorene-based copolymers. The first series of blue emitting polymers has a resemblance to familiar fluorene based polymers with hexyloxyphenyl substituents instead of linear alkyl side chains and the series contains copolymers with a phenoxazine (BPPX) unit derived from more familiar triarylamine structures. Optical measurements show these polymers are free of morphologies such as the beta-phase and we obtain a hole mobility of ~10-3 cm2/Vs, photoluminescence quantum efficiency (PLQE) of 65.7% and optical gain of 41cm-1 for poly(9,9-di(4-hexyloxyphenyl)fluorene). Transient DI-SCLC measurements are used to show differences in charge trapping behaviour in the series. The final chapter of experimental results is based on novel poly(indenofluorene-fluorene) and poly(indenopyrazine-fluorene) copolymers. In the poly(indenofluorene-fluorene) series we consider the role of increased backbone rigidity compared to polyfluorene and the variation of side chain…
Subjects/Keywords: 535
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Export
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Manager
APA (6th Edition):
Chaudhary, M. Y. (2015). Charge transport, injection and optical properties of fluorene based copolymers. (Doctoral Dissertation). Imperial College London. Retrieved from http://hdl.handle.net/10044/1/33205
Chicago Manual of Style (16th Edition):
Chaudhary, Mohammad Yaqub. “Charge transport, injection and optical properties of fluorene based copolymers.” 2015. Doctoral Dissertation, Imperial College London. Accessed March 04, 2021.
http://hdl.handle.net/10044/1/33205.
MLA Handbook (7th Edition):
Chaudhary, Mohammad Yaqub. “Charge transport, injection and optical properties of fluorene based copolymers.” 2015. Web. 04 Mar 2021.
Vancouver:
Chaudhary MY. Charge transport, injection and optical properties of fluorene based copolymers. [Internet] [Doctoral dissertation]. Imperial College London; 2015. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10044/1/33205.
Council of Science Editors:
Chaudhary MY. Charge transport, injection and optical properties of fluorene based copolymers. [Doctoral Dissertation]. Imperial College London; 2015. Available from: http://hdl.handle.net/10044/1/33205
Durham University
28.
Tanasittikosol, Monsit.
Rydberg dark states in external fields.
Degree: PhD, 2011, Durham University
URL: http://etheses.dur.ac.uk/3287/
;
http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545422
► We initially discuss the theory of three-level systems using the dressed state formalism. One of the dressed states, containing a ground state and a Rydberg…
(more)
▼ We initially discuss the theory of three-level systems using the dressed state formalism. One of the dressed states, containing a ground state and a Rydberg state, does not couple with the probe laser; thus, the medium becomes transparent to the latter. This phenomenon is known as electro- magnetically induced transparency (EIT) and this dressed state is known as a Rydberg dark state. We show that EIT can be used to extract the reduced dipole matrix element for transitions to a Rydberg state. However, a prob- lem with three-level Rydberg EIT in a vapour cell is the occurrence of space charges caused by photoelectric ionisation of Rb metal deposited inside the cell. To avoid this problem, we consider adding a third laser resonant with a fourth level. This is to avoid using the laser whose wavelength is less than the threshold wavelength. In cold atoms, the effect of the third laser is to split the usual EIT resonance into a doublet. In thermal atoms, we observe narrow features due to electromagnetically induced absorption and electro- magnetically induced transparency in the Doppler-free configuration. Next we consider the action of a far off-resonance radio frequency (rf) field in the three-level system. We demonstrate the formation of rf-dressed EIT reso- nances in a thermal Rb vapour and show that such states exhibit enhanced sensitivity to dc electric fields compared to their bare counterparts. Fitting the corresponding EIT profile enables precise measurements of the dc field in- dependent of laser frequency fluctuations. We further investigate the theory of rf-dressed Rydberg EIT using the Floquet approach in order to understand the formation of the sideband structure of the Rydberg state. We find that if the time scale of the rf interaction is much shorter than that of the system evolution and decoherence, the sideband structure is well resolved. We also show that the intermediate state exhibits a sideband structure, induced by the Rydberg state, when the Rabi frequency of coupling laser is larger than twice the modulation frequency. Finally we consider resonant microwave cou- pling between the Rydberg states which leads to an Autler-Townes splitting of the EIT resonance in cold atoms. This splitting can be employed to vary the group index by ±105 allowing independent control of the absorptive and dispersive properties of the medium, i.e., one can switch the transparency of the medium or control the group velocity of a pulse propagation by tuning on and off the microwave field.
Subjects/Keywords: 535
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APA (6th Edition):
Tanasittikosol, M. (2011). Rydberg dark states in external fields. (Doctoral Dissertation). Durham University. Retrieved from http://etheses.dur.ac.uk/3287/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545422
Chicago Manual of Style (16th Edition):
Tanasittikosol, Monsit. “Rydberg dark states in external fields.” 2011. Doctoral Dissertation, Durham University. Accessed March 04, 2021.
http://etheses.dur.ac.uk/3287/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545422.
MLA Handbook (7th Edition):
Tanasittikosol, Monsit. “Rydberg dark states in external fields.” 2011. Web. 04 Mar 2021.
Vancouver:
Tanasittikosol M. Rydberg dark states in external fields. [Internet] [Doctoral dissertation]. Durham University; 2011. [cited 2021 Mar 04].
Available from: http://etheses.dur.ac.uk/3287/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545422.
Council of Science Editors:
Tanasittikosol M. Rydberg dark states in external fields. [Doctoral Dissertation]. Durham University; 2011. Available from: http://etheses.dur.ac.uk/3287/ ; http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545422
Heriot-Watt University
29.
Joshi, Chaitanya.
Investigating quantum phenomena in nano- and micromechanical oscillators.
Degree: PhD, 2012, Heriot-Watt University
URL: http://hdl.handle.net/10399/2594
► This thesis theoretically investigates quantum features in nano- and micromechanical oscillators. The thesis aims at proposing novel schemes to prepare mesoscopic mechanical systems in non-classical…
(more)
▼ This thesis theoretically investigates quantum features in nano- and micromechanical oscillators. The thesis aims at proposing novel schemes to prepare mesoscopic mechanical systems in non-classical states including entangled states. The main emphasis of the work is to understand genuine quantum features in coupled harmonic oscillators with in nite dimensional Hilbert spaces. With the recent experimental breakthroughs in achieving the ground state of mesoscopic mechanical systems, the time is now ripe to investigate in detail a full quantum description of such mesoscopic mechanical systems. Thus, the main emphasis of the thesis is on probing salient quantum features in coupled mechanical systems that are assumed to be prepared in vibrational states close to their quantum ground states. A major part of the thesis makes use of var- ious theoretical techniques widely used in quantum optics and quantum information. The majority of the results reported in this thesis involves analytical calculations augmented with numerical investigations. We believe many of the results obtained will be of interest to researchers with background in quantum optics and quantum information and with research interest in the quantum-classical crossover in continuous variable systems.
Subjects/Keywords: 535
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APA ·
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MLA ·
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APA (6th Edition):
Joshi, C. (2012). Investigating quantum phenomena in nano- and micromechanical oscillators. (Doctoral Dissertation). Heriot-Watt University. Retrieved from http://hdl.handle.net/10399/2594
Chicago Manual of Style (16th Edition):
Joshi, Chaitanya. “Investigating quantum phenomena in nano- and micromechanical oscillators.” 2012. Doctoral Dissertation, Heriot-Watt University. Accessed March 04, 2021.
http://hdl.handle.net/10399/2594.
MLA Handbook (7th Edition):
Joshi, Chaitanya. “Investigating quantum phenomena in nano- and micromechanical oscillators.” 2012. Web. 04 Mar 2021.
Vancouver:
Joshi C. Investigating quantum phenomena in nano- and micromechanical oscillators. [Internet] [Doctoral dissertation]. Heriot-Watt University; 2012. [cited 2021 Mar 04].
Available from: http://hdl.handle.net/10399/2594.
Council of Science Editors:
Joshi C. Investigating quantum phenomena in nano- and micromechanical oscillators. [Doctoral Dissertation]. Heriot-Watt University; 2012. Available from: http://hdl.handle.net/10399/2594
University of Leicester
30.
Yazdanfar, Hanieh.
Synthesis and characterisation of stable fluorescent silicon nanoclusters produced using liquid jet method.
Degree: PhD, 2016, University of Leicester
URL: https://figshare.com/articles/Synthesis_and_Characterisation_of_Stable_Fluorescent_Silicon_Nanoclusters_Produced_Using_Liquid_Jet_Method/10237154
;
https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706085
► Fluorescent silicon nanoclusters were produced via a novel liquid jet method (using water or alcohols). The jet initially passes through a plume of atomized silicon…
(more)
▼ Fluorescent silicon nanoclusters were produced via a novel liquid jet method (using water or alcohols). The jet initially passes through a plume of atomized silicon in vacuum. The silicon atoms are captured in the jet, which then agglomerate to nanoclusters, and are ultimately deposited on a cold trap. In this method, several millilitres of sample can be produced in only a few minutes. AFM measurements show the nanoclusters produced have a size of ~1 nm. Samples can be produced in different solvents such as water, ethanol, and isopropanol. Fluorescence emission spectra showed two different fluorescence peaks at 310 nm and 365 - 440 nm; the former is constant, but the latter’s wavelength is highly dependent on the solvent used. This strong solvent sensitivity showed that fluorescence originated from an electronic state localized on the cluster surface. Measurements over long time periods prove these fluorescent particles are chemically and optically stable in solution over several years without further [chemical] stabilization. Samples of silicon deposited in water jets showed a fluorescence quantum yield of 8 - 10% three years after production. Solvent exchange shows the wavelength of fluorescent peaks not only depends on the chemical reactions of silicon particles on/in the liquid jet during nanocluster growth, but also in the solvents in which the nanoclusters were solvated. Solvent transfer experiments show fluorescence peaks shift depending on solvent in a reversible manner. A sample transferred to a specific solvent is equivalent to a sample directly deposited in that solvent. Nanocluster fluorescence lifetime measurements show decay times of a few nanoseconds (between 3.7 to 5.6 ns) that depend on the solvent; Si-water samples have shorter lifetimes with respect to alcoholic samples. Film samples produced by evaporating the solvent show the first and second fluorescence peaks at ~300 - 310 nm and at 420 - 440 nm, respectively. Film samples present longer fluorescence lifetimes and higher fluorescence intensities than liquid samples. Changing the temperature shows the particles have a shorter fluorescence lifetime at higher temperatures and fluorescence intensity decreases with increasing temperature. Chemical analysis of nanoparticles using XPS and ATR revealed that practically all the silicon was oxidized, and clusters produced in water are in the highest oxidation states. Also, the number of silicon particles which interact with the solvent is greater in water than in alcohols. Infrared absorption bands were attributed to SiOH, SiH, SiO, SiO2 and SiOx, (x > 2) species. The solvent exchange experiments suggest that several stable forms of silicon nanoclusters in different oxidation states exist in solution. These can be interchanged by reversible reduction and oxidation depending on the solvent. Our observations suggest that an intrinsically stable form of silicon nanocluster in water exists, and that the deep-blue fluorescence we observed emerges from oxygen-rich states.
Subjects/Keywords: 535
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APA (6th Edition):
Yazdanfar, H. (2016). Synthesis and characterisation of stable fluorescent silicon nanoclusters produced using liquid jet method. (Doctoral Dissertation). University of Leicester. Retrieved from https://figshare.com/articles/Synthesis_and_Characterisation_of_Stable_Fluorescent_Silicon_Nanoclusters_Produced_Using_Liquid_Jet_Method/10237154 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706085
Chicago Manual of Style (16th Edition):
Yazdanfar, Hanieh. “Synthesis and characterisation of stable fluorescent silicon nanoclusters produced using liquid jet method.” 2016. Doctoral Dissertation, University of Leicester. Accessed March 04, 2021.
https://figshare.com/articles/Synthesis_and_Characterisation_of_Stable_Fluorescent_Silicon_Nanoclusters_Produced_Using_Liquid_Jet_Method/10237154 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706085.
MLA Handbook (7th Edition):
Yazdanfar, Hanieh. “Synthesis and characterisation of stable fluorescent silicon nanoclusters produced using liquid jet method.” 2016. Web. 04 Mar 2021.
Vancouver:
Yazdanfar H. Synthesis and characterisation of stable fluorescent silicon nanoclusters produced using liquid jet method. [Internet] [Doctoral dissertation]. University of Leicester; 2016. [cited 2021 Mar 04].
Available from: https://figshare.com/articles/Synthesis_and_Characterisation_of_Stable_Fluorescent_Silicon_Nanoclusters_Produced_Using_Liquid_Jet_Method/10237154 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706085.
Council of Science Editors:
Yazdanfar H. Synthesis and characterisation of stable fluorescent silicon nanoclusters produced using liquid jet method. [Doctoral Dissertation]. University of Leicester; 2016. Available from: https://figshare.com/articles/Synthesis_and_Characterisation_of_Stable_Fluorescent_Silicon_Nanoclusters_Produced_Using_Liquid_Jet_Method/10237154 ; https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.706085
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