CW Mid-Infrared Tandem OPO Source

CW mid-IR sources, capable of delivering 5 Watts of average power, are required in the 2-5 micron range for IR counter measures. To date, solid state laser approaches have been limited to less than 1-2 Watts of average power due to absorption and adverse thermal effects in the nonlinear materials. Our approach to solving this problem is to use a relatively new nonlinear material, bulk periodically poled LiNbO3 (PPLN), as the converter for a conventional cw Nd:YAG pump laser source. The innovation in this work includes: (1) the use of two PPLN OPO devices in series, a "tandem" OPO, capable of delivering wavelengths in all three optical bands of interest, simultaneously; (2) PPLN operated at these wavelengths has an extremely wide angular and temperature acceptance that makes it relatively insensitive to problems encountered with other materials such as AgGaSe2; (3) PPLN has extremely large nonlinear gain that makes it possible to extract significant idler power in the presence of large idler absorption, 30o/ocm. Aculight has developed an OPO model for PPLN operated with large idler absorption that predicts >5 Watts of 4.5 micron output power with 40 Watts of 1 micron input pump power. Aculight will make available a 60 Watt output power cw Nd:YAG pump laser source with excellent beam quality that will allow testing of these devices at power levels a factor of 4-5 higher than that available to date.