Refractive Wavefront Engineering for On-Chip Beam Steering

Optical beam steering (OBS) is a key enabling technology for light detection and ranging (LiDAR) in autonomous systems, demanding a wide field of view, low insertion loss, and high scalability. While on-chip OBS promises compact and integrable solutions, the current technology employing optical phased arrays (OPAs) often suffers from pronounced sidelobes, complex calibration procedures, high loss, and limited scalability. Here, we propose a refractive wavefront engineering approach for on-chip OBS based on a thermo-optic waveguide lens (TOWL) in a multimode waveguide, where beam steering is achieved through parabolic refractive index modulation. By driving a few heater electrodes, the optical axis, effective aperture, and symmetry of such a waveguide lens can be dynamically reconfigured, enabling continuous wavefront shaping, smooth beam deflection, and efficient emission out of the chip facet. Experimentally, a single TOWL beam steering unit achieves a continuous range between ±17.10° at 1550 nm with an insertion loss below 2.1 dB. Such units can easily scale up to cover full 360° emission within a footprint of only 1.2 cm × 1.2 cm. This technology may provide a robust, low-loss, and scalable solution for integrated beam steering applications.