Advanced Zinc Germanium Phosphide for Mid-IR Lasers

Tunable solid state mid-IR lasers are desirable for many applications, including remote sensing, trace gas detection, multispectral imaging and optical communications in poor visibility conditions and molecular spectroscopy. Solid state lasers that operate at wavelengths longer than about 4 ìm typically have low efficiency and low output power and may utilize unstable hygroscopic laser hosts. Therefore, nonlinear optical parametric oscillator devices (OPO) such as ZnGeP2 (ZGP), AgGaSe2, CdSe and LiNbO3 in bulk or as PPLN appear to be the most useful approach to generate output in the mid-IR region. The most successful material is ZGP, because of its high thermal conductivity in comparison to other candidate materials, highest laser damage threshold and largest nonlinear figure of merit. Advanced ZGP samples will be designed and prepared such that they adequately demonstrate the ZGP improvements possible through utilization of the Adhesive-Free Bonding (AFB®) process and special polishing techniques. Developed samples and methods will be compared with existing technology using tests of laser damage, mechanical strength, laser transmission and transmitted wavefront. Improvements analogous to those with ZGP will become available for other nonlinear crystals.