Type of Document Dissertation Author Gregory, Justin Mark Author's Email Address email@example.com URN etd-03192013-124229 Title Effect of Electron and Phonon Excitation on the Optical Properties of Indirect Gap Semiconductors Degree PhD Department Interdisciplinary Materials Science Advisory Committee
Advisor Name Title Norman Tolk Committee Chair Jim Davidson Committee Member Leonard Feldman Committee Member Ronald Schrimpf Committee Member Sokrates Pantelides Committee Member Timothy Hanusa Committee Member Keywords
- ion implantation
- multiphoton absorption
- refractive index
Date of Defense 2013-03-14 Availability unrestricted AbstractThe interaction of electrons and phonons with the properties of semiconducting crystals continues to be a fascinating and highly fruitful field of study. This dissertation addresses two research problems under the general heading of electron and phonon effects on the optical properties of indirect gap semiconductors.
The first problem concerns nonlinear (multi-photon) absorption in germanium crystals, a topic of interest for the telecommunications industry as well as to the basic scientist. Using a combination of infrared transmittance experiments and numerical analysis, the two- and three-photon absorption coefficients β and γ for germanium have been evaluated over the range of wavelengths from 2.8 µm to 5.2 μm. The ratios of the coefficients across the direct/indirect gap transitions and between the two-and three-photon cases, which are less susceptible to experimental uncertainties than the absolute coefficients, have also been determined. Comparison with theoretical studies shows excellent agreement.
The second problem addresses the optical characteristics of ion-bombarded diamond crystals, which is a swiftly developing field due to diamond’s current status as the material of choice for hosting photonic and quantum information devices. The ultrafast optical technique known as coherent acoustic phonon interferometry has been applied to He ion irradiated diamond crystals for the purpose of determining the optical modification induced by the implantation damage. The experimental results provide information about the variation at in the complex refractive indices of the implanted specimens as well as the variation in the photoelastic tensor. A simple phenomenological model quantitatively describing the damage-induced optical modification has been developed which accurately predicts the experimental observations, and may prove to be a useful tool for quantum device design.
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