Low loss orientation-patterned AlGaAs waveguides for quasi phase matched second harmonic generation

Abstract

ABSTRACT We have demonstrated all-epitaxially fabricated orientation-patterned AlGaAs waveguides with reduced waveguide core corrugation for the quasi-phase- matched second harmonic generation (SHG) pumped at 1.55 µm. The attenuation coefficient is measured to be ~4.5 dB/m at 1.55 µm, and ~9.7 dB/cm at 780 nm. The conversion efficiency at continuous wave operation is 43%W -1 with an 8-mm long waveguide. Keywords: Second harmonic generation, nonlinear waveguides, quasi phase matching, AlGaAs, orientation patterned, frequency conversion, molecular beam epitaxy 1. INTRODUCTION GaAs is desirable for nonlinear optical wavelength conversion because of its high nonlinear coefficient. It is also desirable to fabricate nonlinear waveguide devices because of the tight confinement of optical mode in this type of devices would dramatically increase the efficiency. However, because of the isotropic nature of GaAs, birefringent phase matching is not possible in conventional GaAs-based waveguides, thus various artificial approaches have to be adopted. In contrast to bulk GaAs materials, in which phase matching has been achieved only by QPM