Cavities without confinement barrier in incommensurate photonic crystal superlattices

Abstract

We design and fabricate cavities without confinement barrier by combining two incommensurate photonic crystal superlattice waveguides in a two-dimensional photonic crystal slab. A resonant mode with a high-quality factor shows up in the pass band of the waveguides. It has nearly no influence on the propagation of the waveguide mode and can be directly coupled with the waveguide mode. The experimental measurement confirms the theoretical prediction of extraordinary coexistence of localized cavity mode and continuous waveguide mode with high coupling efficiency in the same frequency and space regime.