Photonic Crystal Tapers for Coupling Large Ridge Waveguides to Photonic Crystal Waveguides

Abstract

We present a study of various photonic crystal taper structures each characterized by the taper angle and roughness for coupling light into 2-dimensional photonic crystal waveguides from large ridge waveguides. The photonic crystal waveguide is made of a triangular lattice of holes in a dielectric. The objective is to find a taper structure that offers the best coupling efficiency over a range of widths of the ridge waveguide while leaving a small footprint. We show that such a structure indeed exists and can be further optimized as the width of the ridge waveguide gets even larger leading to more than 90% increase in coupling efficiency in some cases.