Low Power Long Wave Infrared Laser Sources

With new detectors capable of sensing 7.5 - 9 micron wavelengths, a future threat is emerging since these detectors can be used in seekers. The need is to counter this threat with a laser source operating at 7.5 - 9 microns. The source requirements are 5 - 10 Watts of average power and a repetition rate of > 10 kHz. The proposed laser source is a Nd:YAG-pumped tandem OPO system consisting of a periodically-poled LiNbO3 (PPLN) OPO followed by a ZnGeP2 or CdSe OPO pumped by the PPLN idler wave. ZnGeP2 and CdSe are the best available nonlinear materials for power scaling. ZnGeP2 is well-suited for 7.5 - 8.5 microns. CdSe is well-suited for 8 - 9 microns. Preliminary analysis shows that scaling to the multi-Watt level is feasible with either material. CdSe is more difficult to scale because of reduced thermal conductivity and nonlinear drive. The proposed effort addresses power scaling of CdSe. The proposal is to characterize the thermo-optic properties of CdSe at a known thermal load, design a CdSe OPO that compensates for aberrations, and demonstrate the OPO at high thermal loading. The effort will lead to a preliminary design for the Phase II system.