Polarization-insensitive wavelength filters by birefringence compensation of vertical couplers

Abstract

We demonstrate a novel birefringence compensation technique to reduce the polarization dependence of AlGaAs directional coupler wavelength filters operating in the 770 to 970 nm wavelength range. By using a multiple quantum well structure to compensate intrinsic waveguide birefringence, we fabricated vertical coupler filters with polarization-dependent wavelength shifts from 0.1 to 2 nm, significantly less than those achieved for conventional devices. Experimental results show that both the filter wavelength and insertion loss can be rendered polarization insensitive by this technique.