Non-redundant optical phased array

TL;DR

This paper introduces a non-redundant array design for optical phased arrays, significantly increasing resolvable points while reducing phase shifter count, demonstrated through a silicon OPA with 19,000 points.

Contribution

The work proposes a novel NRA-based OPA configuration that scales resolvable points with N^2 and reduces phase shifter complexity, validated experimentally.

Findings

Achieved ~19,000 resolvable points with only 127 phase shifters.

Demonstrated 2D beam steering without wavelength sweeping.

Largest resolvable point count reported for an OPA to date.

Abstract

Optical phased array (OPA) is a promising beam-steering device for various applications such as light detection and ranging (LiDAR), optical projection, free-space optical communication and switching. However, the previously reported OPAs suffer from either an insufficiently small number of resolvable points, or a complicated control requirement due to an extremely large number of phase shifters. This work introduces a novel array configuration for OPA devices based on the non-redundant array (NRA) concept. Based on this design, we can realize high-resolution OPA whose number of resolvable points scales with N2. In contrast, that of traditional OPAs scales only with N. Thus, a significant reduction in the number of required phase shifters can be attained without sacrificing the number of resolvable points. We first investigate the impact of employing the NRA theoretically by considering the autocorrelation function of the array layout. We then develop a Costas-array-based silicon OPA and experimentally demonstrate 2D beam steering with ~19,000 resolvable points using only 127 phase shifters. This corresponds to the largest number of resolvable points achieved by an OPA without sweeping the wavelength to the best of our knowledge.