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You searched for +publisher:"Clemson University" +contributor:("Dr. Liang Dong, Committee Chair"). Showing records 1 – 2 of 2 total matches.

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Clemson University

1. Gu, Guancheng. Advanced Specialty Fiber Designs for High Power Fiber Lasers.

Degree: PhD, Electrical and Computer Engineering, 2016, Clemson University

The output power of fiber lasers has increased rapidly over the last decade. There are two major limiting factors, namely nonlinear effects and transverse mode instability, prohibiting the power scaling capability of fiber lasers. The nonlinear effects, originating from high optical intensity, primarily limit the peak power scaling. The mode instability, on the other hand, arises from quantum-defect driven heating, causing undesired mode coupling once the power exceeds the threshold and degradation of beam quality. The mode instability has now become the bottleneck for average output power scaling of fiber lasers. Mode area scaling is the most effective way to mitigate nonlinear effects. However, the use of large mode area may increase the tendency to support multiple modes in the core, resulting in lower mode instability threshold. Therefore, it is critical to maintain single mode operation in a large mode area fiber. Sufficient higher order mode suppression can lead to effective single-transverse-mode propagation. In this dissertation, we explore the feasibility of using specialty fiber to construct high power fiber lasers with robust single-mode output. The first type of fiber discussed is the resonantly-enhanced leakage channel fiber. Coherent reflection at the fiber outer boundary can lead to additional confinement especially for highly leaky HOM, leading to lower HOM losses than what are predicted by conventional finite element mothod mode solver considering infinite cladding. In this work, we conducted careful measurements of HOM losses in two leakage channel fibers (LCF) with circular and rounded hexagonal boundary shapes respectively. Impact on HOM losses from coiling, fiber boundary shapes and coating indexes were studied in comparison to simulations. This work demonstrates the limit of the simulation method commonly used in the large-mode-area fiber designs and the need for an improved approach. More importantly, this work also demonstrates that a deviation from circular fiber outer shape may be an effective method to mitigate HOM loss reduction from coherent reflection from fiber outer boundary. In an all-solid photonic bandgap fiber, modes are only guided due to anti-resonance of cladding photonic crystal lattice. This provides strongly mode-dependent guidance, leading to very high differential mode losses, which is essential for lasing far from the gain peak and suppression of stimulated Raman scattering. We will show that all-solid photonic bandgap fibers with effective mode area of ~920μm2 can be made with excellent higher order mode suppression. We then demonstrate a 50μm-core-diameter Yb-doped all-solid photonic bandgap fiber laser. 75W output power has been generated with a diffraction-limited beam and an efficiency of 70% relative to the launched pump power. We have also experimentally confirmed that a robust single-mode regime exists near the high frequency edge of the bandgap. It is well known that incorporation of additional smaller cores in the cladding can be… Advisors/Committee Members: Dr. Liang Dong, Committee Chair, Dr. John Ballato, Dr. Eric Johnson, Dr. Lin Zhu.

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APA (6th Edition):

Gu, G. (2016). Advanced Specialty Fiber Designs for High Power Fiber Lasers. (Doctoral Dissertation). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_dissertations/1757

Chicago Manual of Style (16th Edition):

Gu, Guancheng. “Advanced Specialty Fiber Designs for High Power Fiber Lasers.” 2016. Doctoral Dissertation, Clemson University. Accessed January 28, 2020. https://tigerprints.clemson.edu/all_dissertations/1757.

MLA Handbook (7th Edition):

Gu, Guancheng. “Advanced Specialty Fiber Designs for High Power Fiber Lasers.” 2016. Web. 28 Jan 2020.

Vancouver:

Gu G. Advanced Specialty Fiber Designs for High Power Fiber Lasers. [Internet] [Doctoral dissertation]. Clemson University; 2016. [cited 2020 Jan 28]. Available from: https://tigerprints.clemson.edu/all_dissertations/1757.

Council of Science Editors:

Gu G. Advanced Specialty Fiber Designs for High Power Fiber Lasers. [Doctoral Dissertation]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_dissertations/1757

2. Dunn, Christopher David. Tellurite Fiber for High Power Mid-Wave Infrared Supercontinuum Generation.

Degree: MS, Photonic Science and Technology, 2016, Clemson University

Broadband, high-power, mid-infrared sources are critical for many applica-tions. Fiber based supercontinuum generation is the optimum mid-infrared broad-band source that can provide extended bandwidth and good coherence. Compared to alternatives such as fluorides and chalcogenides, tellurite fibers are more robust and can handle much higher power. Tellurite fibers also have high nonlinearity and a ma-terial zero dispersion wavelength close to 2 µm. This makes them ideal for nonlinear processes pumped by Tm-doped silica fiber lasers. We demonstrated tellurite fibers by using a simple stack and draw process. This fabrication method requires simple setup and is easily repeatable. Due to the difficulty in producing soft glass tubes, we have drawn a stack-and-draw preform without the need for an over-clad tube. The stack-and-draw process provides several advantages over other solid and micro-structured designs. Our solid tellurite fiber design shows potential for broadband mid-infrared supercontinuum generation. We have also shown that designs with low dispersion are the key for broadband mid-infrared supercontinuum generation in tellurite fibers pumped at 2 µm. Advisors/Committee Members: Dr. Liang Dong, Committee Chair, Dr. John Ballato, Dr. Lin Zhu.

…draw tower used at Clemson University can be seen in Figure 2.3. The preform is lowered into… …speed that the fiber is pulled along the 20 Figure 2.3: Clemson University draw tower with… …use of tubes. Here at Clemson University, we have developed the stack-and-draw method to be… …Depiction of the rod-in-tube preform fabrication method [40]. . . . . . Clemson… …University draw tower with soft glass furnace in place. . . . Depiction of the neck-down region in… 

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APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Dunn, C. D. (2016). Tellurite Fiber for High Power Mid-Wave Infrared Supercontinuum Generation. (Masters Thesis). Clemson University. Retrieved from https://tigerprints.clemson.edu/all_theses/2474

Chicago Manual of Style (16th Edition):

Dunn, Christopher David. “Tellurite Fiber for High Power Mid-Wave Infrared Supercontinuum Generation.” 2016. Masters Thesis, Clemson University. Accessed January 28, 2020. https://tigerprints.clemson.edu/all_theses/2474.

MLA Handbook (7th Edition):

Dunn, Christopher David. “Tellurite Fiber for High Power Mid-Wave Infrared Supercontinuum Generation.” 2016. Web. 28 Jan 2020.

Vancouver:

Dunn CD. Tellurite Fiber for High Power Mid-Wave Infrared Supercontinuum Generation. [Internet] [Masters thesis]. Clemson University; 2016. [cited 2020 Jan 28]. Available from: https://tigerprints.clemson.edu/all_theses/2474.

Council of Science Editors:

Dunn CD. Tellurite Fiber for High Power Mid-Wave Infrared Supercontinuum Generation. [Masters Thesis]. Clemson University; 2016. Available from: https://tigerprints.clemson.edu/all_theses/2474

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