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

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scopies as a probe of these features stems from its high sensitivity to symmetry. The
symmetry of a material determines its unique nonzero second-order susceptibility elements,
whose amplitude and transformation properties in turn determine the sample
second-harmonic emission properties.
In this thesis, we are concerned with the optical properties of solid/solid interfaces,
the determination of material symmetry, the observation of defect states, and
bulk nonlinear optical spectroscopy. Experimentally, we have performed ultrafast
nonlinear optical spectroscopy of GaN, and we have constructed a nonlinear optical
microscope. The ultrafast nonlinear optical spectroscopy represents the majority of
our effort and has produced a thorough investigation of the linear and nonlinear optical
properties of GaN. In addition, we have designed and constructed a nonlinear
optical microscope to examine the nonlinear optical properties of a variety of systems
including carbon nanotubes. The latter area is an ongoing experiment that may lead
to the comparison of carbon nanotube second-order susceptibility elements and the
examination of nanotube symmetry. vVe briefly summarize each project.
Our nonlinear optical experiments of GaN were motivated by the recent investigations
of the optical, electrical, structural, and defect properties of GaN [13. 1·1. 15.
16. 17]. These investigations stem from GaN's attractiveness as a material for electrooptic
devices [18, 19]. Previous measurements of the nonlinear optical properties of
GaN have been limited to a single fundamental wavelength of 1064 nm [20, 2L 22. 23]
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