Abstract

Mid infra-red (IR) sources between 1 μm and 10 μm have wide applications in spectroscopy, remote sensing and military countermeasures. Established nonlinear IR crystals such as AgGaSe₂, and AgGaS₂ have poor thermal properties, and low damage thresholds. ZnGeP₂ appears promising for high power applications, but its growth technology is still being developed, and crystals are expensive. In comparison, GaAs has a large nonlinear coefficient, good optical transmission between 1 μm and 12 μm, and high optical damage threshold. It also has good chemical stability, good mechanical properties, and a well developed growth technology. Unfortunately, single crystal GaAs is linearly isotropic; therefore, nonlinear interactions cannot be birefringently phase-matched. However, the interacting waves can be quasi-phasematched (QPM) by periodically modulating the nonlinear coefficient in a stack of rotated plates¹,². By diffusion bonding individual plates together, we can minimize scattering and reflection losses at the air-GaAs interfaces. Preliminary diffusion-bonded-stacked (DBS) GaAs devices demonstrated close to theoretical conversion efficiency³,⁴, but had high transmission losses. We report improved processing, leading to a significant reduction in the transmission loss to less than 0.2% per layer at 5 μm.

© 1996 Optical Society of America