Silicon optical phased array with a 180-degree field of view for 2D optical beam steering

Optical phased arrays (OPAs), the optical counterpart of phased arrays at radio frequencies, can electronically steer an optical beam without any moving parts. To achieve a 180^◦ field of view (FOV), the array emitters should be spaced a half-wavelength apart or less. However, a conventional OPA based on a waveguide grating array suffers from strong cross talk between adjacent waveguides when the pitch is a half-wavelength or less. Here, we theoretically describe and experimentally demonstrate a two-dimensional aliasing-free beam steering regime for an integrated OPA with the entire 180^◦ FOV. We achieve this by using a half-wavelength-pitch waveguide array combined with a trapezoidal slab grating as a single emitter. Our OPA also features a low sidelobe level of <−19 dB while the beam is steered from −40^◦ to +40^◦, breaking the trade-off between FOV and beam quality. The chip-based OPA with a large beam steering range and high beam quality provides a promising route for a compact, solid-state, cost-effective, and high-performance light detection and ranging system, enabling a wide range of classical and quantum applications.