Delta n=0.22 birefringence measurement by surface emitting second harmonic generation in selectively oxidized GaAs/AlAs optical waveguides

The authors have measured the birefringence enhancement due to lateral selective oxidn. of AlAs in GaAs/AlAs optical waveguides. The birefringence was measured by imaging the surface-emitted 2nd harmonic generated by the nonlinear interaction of counterpropagating TE and TM modes. In a waveguide contg. a single AlAs layer the birefringence is enhanced from Delta n = 0.017 (before oxidn.) to Delta n = 0.038 (after oxidn.). In an oxidized multilayer GaAs/AlAs waveguide, a birefringence as high as Delta n = 0.22 is measured. This birefringence is sufficient to phase-match the difference frequency generation of 3-5 micro m IR radiation from 2 near-IR pumps. [on SciFinder (R)]