Spectrally Scanning LiDAR Based on Wide-Angle Agile Diffractive Beam Steering

Spectral scan, or beam steering by only wavelength tuning enables inertia-less fast-scanning LiDAR, while the field of view is fundamentally limited by the total available wavelength range and the dispersion ability of common gratings. Here, we propose to relieve the restriction by combining a diffraction grating and a low-cost diffractive element, which enables wide-angle two-dimensional beam steering. An FoV far beyond the reach of other spectral scan methods can be achieved. Several diffractive elements samples are fabricated to demonstrate spectrally scanning field of views of $7.7^{\circ } \times 10^{\circ }$ and $7.7^{\circ } \times 29^{\circ }$ from an 100-nm wavelength tuning range. Also, to show the potential to further extend the spectral scan range, blazed diffractive elements are fabricated with high diffraction efficiency, which corresponds to a spectral scan range up to 40.3°. Based on the structure, a solid-state coherent LiDAR system is built. Three-dimensional imaging with mm-level range resolution is demonstrated.