Optical Characterization of Thick Growth Orientation-Patterned Gallium Arsenide

Tunable laser sources in the mid-infrared (MIR) spectral range are required for several Air Force applications. Existing lasers with output in the near-infrared can be converted to more desirable MIR by using nonlinear effects. Orientation patterned gallium arsenide (OPGaAs) is a promising nonlinear conversion material because it has broad transparency and can be engineered for specific pump laser and output wavelengths using quasi-phase matching techniques. This research examines the optical quality of seven OPGaAs crystal samples and explores the design of an optical parametric oscillator (OPO) device. The Air Force Research Laboratory Electro-Optical Countermeasures Technology Branch obtained the samples from two independent, industrial suppliers. Direct transmission and scattering measurements at 2.05-??m were taken as a function of position across the incident face of each sample. Scattering, absorption, and reflection coefficients for each sample were quantified. The sample with the most favorable coefficients was selected for use in an OPO. Nonlinear output from the OPO was not achieved before the optical coating failed. A direct comparison of OPGaAs crystal performance based on source of manufacturing is reported. Results are discussed to aid in improvements to OPGaAs fabrication techniques. Optical quality data are graphically presented to illustrate total performance resulting from crystal design features. OPO design parameters are summarized with recommendations for future efforts.