Inverse-Designed Photonic Crystal Circuits for Optical Beam Steering

TL;DR

This paper demonstrates the use of inverse design to create photonic crystal waveguides with engineered dispersion and coupling, enabling a wide-range optical beam steering in integrated photonic circuits.

Contribution

It introduces inverse design techniques to optimize photonic crystal waveguides for slow-light applications and efficient coupling, achieving significant beam steering capabilities.

Findings

Achieved a group index of 25 over 20nm and 12nm bandwidths for even and odd mode PCWs.

Designed strip and vertical couplers for efficient light coupling.

Constructed OPAs with a 20° steering range within a 20nm bandwidth.

Abstract

The ability of photonic crystal waveguides (PCWs) to confine and slow down light makes them an ideal component to enhance the performance of various photonic devices, such as optical modulators or sensors. However, the integration of PCWs in photonic applications poses design challenges, most notably, engineering the PCW mode dispersion and creating efficient coupling devices. Here, we solve these challenges with photonic inverse design, and experimentally demonstrate a slow-light PCW optical phased array (OPA) with a wide steering range. Even and odd mode PCWs are engineered for a group index of 25, over a bandwidth of 20nm and 12nm, respectively. Additionally, for both PCW designs, we create strip waveguide couplers and free-space vertical couplers. Finally, also relying on inverse design, the radiative losses of the PCW are engineered, allowing us to construct OPAs with a 20{\deg} steering range in a 20nm bandwidth.