Mid-Wave ZGP OPOs Pumped by a Cr:ZnSe Laser

摘要

We describe Type I and Type II ZnGeP(2) OPO's operating in the 4-6 micrometers region. The OPOs are pumped by a gain-switched Cr(2+):ZnSe laser.... .... Broadly tunable mid-infrared laser sources are of interest for a variety of applications including differential absorption lidar, differential scattering lidar, multi-spectral detection and imaging, optical communications in poor visibility conditions and spectroscopy. A variety of laser and nonlinear optical devices have been demonstrated that access thiS spectral region. To date, however, direct solid-state lasers that operate at wavelengths longer than 4 microns have not been practical for field deployment under harsh conditions. Typical problems include low electrical efficiency, low output power, operation at cryogenic temperatures and use of hygroscopic gain media. Consequently, nonlinear optical devices, in particular optical parametric oscillators, have been developed as a more robust means of generating moderate to high power in id-wave infrared (MWIR) output. Typical MWIR OPO materials include ZnGeP2 (ZGP), AgGaSe2, CdSe and LiNbO3 (in both bulk and periodically poled forms). Of these materials, ZGP has the highest thermal conductivity (by an order of magnitude), the highest damage threshold, and the largest nonlinear figure-of-merit (by a factor of six). A significant disadvantage of ZGP, however, is that it is not transparent at wavelengths shorter than 2 microns and suffers absorption at wavelengths shorter than 2.1 um. This eliminates the possibility of pumping ZGP with many well-developed solid-state lasers.