We propose using the huge birefringence available in GaAs/AlAs oxidized waveguides to phase-match nonlinear optical conversions in the near- and mid-infrared. Tunable midinfrared radiation can be obtained by difference frequency generation from two tunable near-infrared semiconductor lasers. We measured the transmission spectrum of the AlAs oxide, and demonstrated the birefringence enhancement due to oxidation in a single polarization waveguide.
Fiore, A., Berger, V., Rosencher, E., Laurent, N., Vodjdani, N., & Nagle, J. (1996). Birefringence phase matching in selectively oxidized GaAs/AlAs optical waveguides for nonlinear frequency conversion. Journal of Nonlinear Optical Physics & Materials, 5(4), 645-651. https://doi.org/10.1142/S0218863596000477