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

TL;DR

This paper presents the design and simulation of vertical couplers for triangular nano-beam waveguides, achieving nearly 50% efficiency, facilitating testing of integrated photonic circuits with current fabrication methods.

Contribution

It introduces novel design rules and simulation results for vertical couplers in triangular waveguides, addressing a gap in existing photonic component design.

Findings

Coupling efficiencies approaching 50% achieved

Design compatible with current angled-etch fabrication

Enables efficient testing of integrated photonic components

Abstract

Photonic waveguides 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 waveguides, such as couplers and gratings, are not well established. Here we present simulations of elements designed to couple light into, and out of, triangular waveguides from the vertical direction, which can be implemented with current angled-etch fabrication technology. The devices demonstrate coupling efficiencies approaching \unit{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.