New Nonlinear Optical Materials for the Mid-Infrared

by Peter G. Schunemann (BAE Systems, Inc., Nashua, USA)

Monday 12 Oct 2015, 15:00 → 16:30 Europe/Berlin

CFEL Building (99), Ground Floor, SR III (DESY Hamburg)

Mid-infrared nonlinear optical crystals have matured in the last twenty-five years from scientific curiosities into practical robust materials generating efficient laser output in the 2-12 micron spectral range. ZnGeP2 (ZGP) in particular has emerged as the NLO material of choice for frequency conversion between 2µm and 8µm. ZGP, however, still has two main limitations: 1) its transparency and phase-matching range make it incompatible with 1- and 1.5µm laser pumping; and 2) its usefulness for generating output in the 8-12µm is limited by severe multi-phonon absorption. These limitations have been overcome by several new mid-infrared nonlinear crystals: CdSiP2 (CSP) is a bulk birefringent chalcopyrite analog of ZGP grown by horizontal gradient freeze growth in a transparent furnace. Its larger band gap (512 nm) and birefringence allows for 1- and 1.5-µm pumping, and its nonlinear coefficient and thermal conductivity are dramatically higher than existing materials. Orientation-patterned GaAs (OP-GaAs) and GaP (OP-GaP) are quasi-phase-matched. OP-GaAs has the highest gain among all QPM materials, and can be pumped at 2-m to generate output at 8-12 µm and beyond, whereas OP-GaP is a low-loss QPM ZGP analog than can be pumped with 1µm lasers.