Birefringence phase-matched frequency doubling at /spl lambda/=1.6 /spl mu/m in GaAs-based waveguides

Frequency conversion in GaAs waveguides is a promising approach to the realization of tunable sources in the mid-IR and wavelength shifters for optical-fiber communications. The high second-order nonlinear susceptibility of GaAs and the possibility of integration with sources imply high conversion efficiencies and may lead to all-semiconductor integrated optical parametric oscillators. It was recently demonstrated that very high form birefringence can be obtained in (Al)GaAs/Al/sub 2/O/sub 3/ multilayers, realized by selective wet oxidation of (Al)GaAs/AlAs. This has led to demonstration of mid-IR sources by difference-frequency generation. Here we demonstrate that the same concept can be used to phase match frequency conversion in the 1.55-/spl mu/m telecommunication window. In this case, a much higher birefringence and a new design for the cladding layers are needed to compensate for the high dispersion of AlGaAs near the bandgap.