Mid-IR difference-frequency generation in GaAs/oxidized AlAs waveguides

Summary form only given. As a semiconductor with a centrosymmetric crystal structure, bulk GaAs is nonbirefringent and is therefore rarely used for nonlinear frequency conversion despite its attractive nonlinear coefficient. By building a multilayer system GaAs/oxidized AlAs (Alox), we have shown that high form birefringences can be obtained in the composite material. To obtain a birefringence sufficient for phase matching in frequency conversion, a high index contrast is required between the two materials in the multilayer stack, which can be obtained by the oxidation of AlAs. We show phase-matched frequency conversion processes using form birefringence in composite GaAs/Alox waveguides. We believe these experiments are the first experimental demonstration of Van der Ziel´s proposal (1975) of using form birefringence for nonlinear phase matching.