Design of free-space couplers for suspended triangular nano-beam waveguides

Abstract

Abstract Photonic waveguides (WGs) with triangular cross section are being investigated for material systems such as diamond, glasses and gallium nitride, which lack easy options to create conventional rectangular nanophotonic waveguides. The design rules for optical elements in these triangular WGs, such as couplers and gratings, are not well established. Here we present simulations of elements designed to couple light into, and out of, triangular WGs from the vertical direction, which can be implemented with current angled-etch fabrication technology. The devices demonstrate coupling efficiencies approaching 50% for light focused from a high numerical aperture objective. The implementation of such couplers will enable fast and efficient testing of closely spaced integrated circuit components.