William Angerer - Department of Physics and Astronomy - University ...

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interference by group velocity mismatch may be used to easily measure ultrafast laser
pulse durations.
Chapter 3 describes our experimental apparatus for nonlinear optical investigations
of GaN. We highlight the characteristics of the Ti:AI 2 0 3 laser and describe
techniques for its operation.
Chapter 4 investigates the linear optical properties of GaN. The propagation of
second-harmonic light is highly dependent on linear optical properties. We discuss
techniques for measuring thin film thicknesses of GaN films deposited on a transparent
sapphire substrates. A dispersion relationship for the index of refraction of GaN is
determined by a novel transmission method. Finally, we distinguish our GaN samples
by photoluminescence measurements. Our samples are characterized by the presence
or absence of a yellow luminescence band at 2.2 eV.
The properties of GaN are described in Chapter 5. Emphasis is placed on the
electronic and optical properties of GaN. We also discuss the defect structure of Ga;\".
In addition, we introduce group theory techniques to determine optical selection rules.
vVe use these techniques to calculate contributions to the three unique second-order
susceptibility elements of GaN, x~;)z, x~7jx' and x1~x' that are resonantly enhanced
when the second-harmonic photon energy is approximately equal to the band gap
energy of GaN.
Chapter 6 presents our nonlinear optical experiments in GaN. We demonstrate
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