Integrated coherent LiDAR with broadband low-noise-laser-driven, multidimensionally multiplexed passive beam steering

<title>Abstract</title> <p>Frequency-modulated continuous-wave (FMCW) LiDAR is a promising route towards chip-scale three-dimensional sensing, but its scalability is constrained by two coupled bottlenecks: the control complexity of beam-steering devices, such as active optical phased arrays, and the difficulty of combining wide wavelength tuning with the low-frequency noise required for precise coherent ranging. Here we report a hybrid integrated coherent LiDAR architecture that combines a self-injection-locked external-cavity laser (SILECL) with a multidimensionally multiplexed passive dispersive optical phased array. The laser separates broadband wavelength selection from linewidth compression, providing a 66-nm tuning range and sub-100-Hz intrinsic linewidth across the tuning window, with a minimum linewidth of 50 Hz. The passive emitter uses slanted gratings, bidirectional excitation, and polarization multiplexing to enable 16-fold spectral reuse; when characterized with an external 184-nm wavelength sweep, it demonstrates a 110° × 90° field of view. In FMCW ranging experiments using the SILECL, self-injection locking improves the sweep linearity to above 99.9% and reduces the ranging precision from 8.39 cm to 0.97 cm at 2.1 m. These results highlight a co-design principle for coherent LiDAR, in which source coherence, wavelength agility and passive spatial multiplexing are jointly optimized to reduce beam-steering complexity.</p>