Abstract

ZnGeP₂ is currently one of the most promising nonlinear optical materials for efficient frequency conversion into the mid-IR spectral region¹. Because of its exceptionally high thermal conductivity² and virtual absence of thermal lensing³, ZnGeP₂ is a viable material choice for many applications requiring high average powers and high pulse repetition frequencies. In the past, applications involving 2-µm pumping have been hampered by the presence of a large stoichiometry-related absorption near the band edge. Recently however, an intensive effort in ZnGeP₂ crystal growth has produced large, crack-free crystals with sufficiently low 2-µm absorption (≈0.25 cm^-1) to allow efficient operation as a 2-µm pumped OPO at uncontrolled ambient temperature.¹ The present experiments demonstrate higher slope (37%) and overall (26%) conversion efficiencies using a low loss crystal at ambient temperature. We also show that by cooling, comparable efficiencies can be achieved in crystals having substantially higher near band edge absorptions.

© 1993 Optical Society of America