Narrow beam and low-sidelobe electro-optic beam steering on thin-film lithium niobate optical phased array

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 as versatile and miniaturized platform to this end, yet conventional versions still suffer from a narrow steering field of view, insufficient sidelobe suppression, and limited angular resolution in electro-optic (EO) beam steering. Thin-film lithium niobate (LN), with its strong 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 method, we transform a uniformly spaced waveguide 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 with fine width of 0.99°×0.63° from an aperture of only 140 μm×250 μm, achieving a wide 2D steering range of 47°×9.36° with a 20 dB sidelobe-suppression ratio. These results highlight thin-film LN OPA as a compelling route toward ultra-compact, high-performance high-speed EO beam-steering modules and optical free-space modulators.