Progress in orientation-patterned GaP for next-generation nonlinear optical devices

Orientation-patterned GaP is a promising nonlinear material for frequency conversion in the mid and longwave IR (2-5 mu m and 8-12 mu m) by quasi-phase matching. As an alternative to OPGaAs, OPGaP has the advantage of having lower two-photon absorption in the convenient pumping range 1 - 1.7 mu m. We report recent results on development of thick QPM GaP for high power tunable laser sources radiating in the mid IR. Two are the major challenges to producing OPGaP: development of simple techniques for preparation of patterned templates and a technology for fast epitaxial growth of thick, high quality GaP on these templates. The focus was to adapt/simplify the wafer fusion process for OPGaP template preparation. Then increase the growth rate and layer thickness of regrown material, while maintaining vertical domain propagation. The growth experiments were conducted in a horizontal quartz reactor, using a standard hydride vapor phase epitaxial process. The growth was performed on: (i) plain (100) GaP; (ii) half-patterned (HP) and (iii) orientation-patterned (OP) templates, fabricated on (100) GaP. Up to 370 mu m thick layers with high crystal and optical quality were reproducibly grown on plain material. Growth on HP templates resulted in up to 470 mu m thick layers with rectangular mesa's shape. These results were used to determine the optimal substrate and pattern orientations. HVPE growth on OP templates achieved stable growth rates of 50-70 mu m/h with domain walls propagating vertically, following the periodicity of the initial pattern, and resulted in the first 350 mu m thick device quality OPGaP.