Low-loss wavelength-selective integrated waveguide coupler based on tilted Bragg gratings

Abstract

We propose and investigate numerically a new kind of integrated optical waveguide coupler. Two waveguides with tilted Bragg gratings couple selectively to a discrete counterpropagating cladding mode that acts as an intermediary to transfer power between the waveguides. This gives a highly versatile platform that can act as a low-loss coupler with an arbitrary coupling ratio between 0% and 100%, as a narrow-bandwidth wavelength filter, and as a phase-selective switch that transmits two light waves of a fixed relative phase but reflects the orthogonal phase within a single device.