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University of North Texas

1. Wu, Yuan-Yen. Optical Nonlinearities in Semiconductors for Limiting.

Degree: 1990, University of North Texas

I have conducted detailed experimental and theoretical studies of the nonlinear optical properties of semiconductor materials useful for optical limiting. I have constructed optical limiters utilizing two-photon absorption along with photogenerated carrier defocusing as well as the bound electronic nonlinearity using the semiconducting material ZnSe. I have optimized the focusing geometry to achieve a large dynamic range while maintaining a low limiting energy for the device. The ZnSe monolithic optical limiter has achieved a limiting energy as low as 13 nJ (corresponding to 300W peak power) and a dynamic range as large as 105 at 532 nm using psec pulses. Theoretical analysis showed that the ZnSe device has a broad-band response covering the wavelength range from 550 nm to 800 nm. Moreover, I found that existing theoretical models (e.g. the Auston model and the band-resonant model using Boltzmann statistics) adequately describe the photo-generated carriers refractive nonlinearity in ZnSe. Material nonlinear optical parameters, such as the two-photon absorption coefficient β2=5.5cm/GW, the refraction per unit carrier density σn=-0.8∗10-21cm3 and the bound electronic refraction n2=-4∗10-11esu, have been measured via time-integrated beam distortion experiments in the near field. A numerical code has been written to simulate the beam distortion in order to extract the previously mentioned material parameters. In addition, I have performed time-resolved distortion measurements that provide an intuitive picture of the carrier generation process via two-photon absorption. I also characterized the optical nonlinearities in a ZnSe Fabry-Perot thin film structure (an interference filter). I concluded that the nonlinear absorption alone in the thin film is insufficient to build an effective optical limiter, as it did not show a net change in refraction using psec pulses. An innovative numerical program was developed to simulate the nonlinear beam propagation inside the Fabry-Perot structure. For comparison, pump-probe experiments were performed using both thin film and bulk ZnSe. The results showed relatively long carrier lifetimes (>300 psec) in both samples. A numerical code was written to fit the pump-probe experimental results. The fitting yielded that carrier lifetimes (recombination through traps), radiative decay rate, two-photon absorption coefficient as well as the free carrier absorption coefficient for ZnSe bulk material. Advisors/Committee Members: Van Stryland, Eric W., Soileau, M. J., West, Bruce J., Duggan, Jerome L., Kobe, Donald Holm.

Subjects/Keywords: semiconductors; optical limiting; absorptive nonlinearity; refractive nonlinearity; nonlinear material; Semiconductors  – Optical properties.

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

APA (6th Edition):

Wu, Y. (1990). Optical Nonlinearities in Semiconductors for Limiting. (Thesis). University of North Texas. Retrieved from https://digital.library.unt.edu/ark:/67531/metadc331203/

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):

Wu, Yuan-Yen. “Optical Nonlinearities in Semiconductors for Limiting.” 1990. Thesis, University of North Texas. Accessed October 24, 2020. https://digital.library.unt.edu/ark:/67531/metadc331203/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

MLA Handbook (7th Edition):

Wu, Yuan-Yen. “Optical Nonlinearities in Semiconductors for Limiting.” 1990. Web. 24 Oct 2020.

Vancouver:

Wu Y. Optical Nonlinearities in Semiconductors for Limiting. [Internet] [Thesis]. University of North Texas; 1990. [cited 2020 Oct 24]. Available from: https://digital.library.unt.edu/ark:/67531/metadc331203/.

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

Council of Science Editors:

Wu Y. Optical Nonlinearities in Semiconductors for Limiting. [Thesis]. University of North Texas; 1990. Available from: https://digital.library.unt.edu/ark:/67531/metadc331203/

Note: this citation may be lacking information needed for this citation format:
Not specified: Masters Thesis or Doctoral Dissertation

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