University PhD Dissertation Defense / Paulina S. Kuo (Monday, Oct. 15)
pskuo at stanford.edu
Fri Oct 5 10:50:18 PDT 2007
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Department of Applied Physics
University Ph.D. Dissertation Defense
Thick-Film, Orientation-Patterned Gallium Arsenide
for Nonlinear Optical Frequency Conversion
Paulina Susan Kuo
Research Advisor: Professor Martin M. Fejer
15 October 2007
4:15 pm (refreshments at 4:00 pm)
Applied Physics, Room 200
Optical frequency conversion using quasi-phasematched (QPM)
nonlinear optical crystals is a powerful technique for generating coherent
radiation in wavelength ranges where lasers are not readily available.
Quasi-phasematched GaAs is an ideal material for generating infrared light
for applications in spectroscopy and infrared countermeasures.
Orientation-patterned gallium arsenide (OP-GaAs) is a type of QPM GaAs that
has been recently developed. In OP-GaAs, periodic inversions of the
crystallographic orientation are epitaxially grown into the material. The
growth process involves molecular beam epitaxy, lithographic definition of
QPM periods, and hydride vapor phase epitaxy. Significant progress has been
made in increasing the quality of OP-GaAs material; periods as small as 30
microns have been grown in 0.5 mm thick films and overall thicknesses of 1
mm have been achieved. Furthermore, OP-GaAs loss measurements show
attenuation coefficients of 0.005 cm-1, measured at 2-micron wavelength.
This thesis discusses growth improvements in OP-GaAs and the
characterization of these improvements.
The improved material quality in OP-GaAs has allowed the
demonstration of efficient nonlinear optical frequency conversion in the
mid-infrared wavelength range. Several nonlinear optical devices were
demonstrated in bulk OP-GaAs. Pumped near 3-micron wavelength, an extremely
broadband infrared spectrum (spanning 4.5-11 microns) was obtained using
optical parametric generation in OP-GaAs. I will also discuss an experiment
exploring polarizations combinations of the interacting light waves in
OP-GaAs. High symmetry in the nonlinear susceptibility tensor in GaAs
together with isotropy in its refractive index allow efficient nonlinear
optical mixing with circularly polarized or even depolarized waves.
Efficient pumping of an OP-GaAs OPO with circularly polarized and
depolarized light was achieved.
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