Narrow beam and low-sidelobe two-dimensional beam steering on thin-film lithium niobate optical phased array

TL;DR

This paper demonstrates a compact, high-resolution 2D optical phased array on thin-film lithium niobate with wide steering range, low sidelobes, and improved angular resolution for advanced optical communication and sensing applications.

Contribution

It introduces a non-uniformly spaced LN-based 2D EO-steered OPA with optimized design for enhanced steering range and sidelobe suppression, advancing integrated photonics.

Findings

Achieved 0.99°×0.63° main-lobe beam width.

Realized 47°×9.36° 2D steering range.

Sidelobe suppression ratio of 20 dB.

Abstract

Optical beam steering has become indispensable in free-space optical communications, light detection and ranging (LiDAR), mapping, and projection. Optical phased array (OPA) leads this field, yet conventional versions still suffer from a narrow steering field of view (FOV), insufficient sidelobe suppression, and limited angular resolution. Thin-film lithium niobate (LN), with its strong Pockels electro-optic (EO) effect, offers a powerful integrated-photonics platform to overcome these limitations. Here we present a two-dimensional (2D) EO-steered OPA based on a non-uniformly spaced X-cut thin-film LN ridge-waveguide array. A superlattice ridge design suppresses optical crosstalk to -20 dB, enabling low-sidelobe far-field radiation. Using particle swarm optimization (PSO) method, we transform a uniformly spaced array into an optimized non-uniform design, largely improving angular resolution while maintaining sidelobe suppression. When combined with a single-radiating trapezoidal end-fire emitter incorporating an etched grating, the device produces a main-lobe beam width of 0.99 degree*0.63 degree from an aperture of only 140 um*250 um, achieving a wide 2D steering range of 47 degree*9.36 degree with a 20 dB sidelobe-suppression ratio. These results highlight thin-film LN OPA as a compelling route toward heterogeneous, compact, and high-performance EO beam-steering modules and ultra-miniaturized optical modulators.