Mechanically reconfigurable metasurface LiDAR for adaptive 3D imaging

In the realm of active 3D imaging, the light detection and ranging (LiDAR) technology plays a pivotal role, offering direct depth acquisition and robust resistance to environmental noises. LiDAR systems are generally categorized into beam scanning LiDAR and flash LiDAR, each with its own advantages and limitations. Beam scanning LiDAR provides high accuracy and long detection range with limited efficiency, while flash LiDAR can achieve high efficiency detection through snapshot approach at the expense of reduced detection accuracy and distance. An ideal LiDAR system would achieve high accuracy, extended detection range, and high efficiency simultaneously, urging the development of novel beam-forming devices. Advances in nanophotonics, especially metasurfaces, are driving LiDAR towards miniaturization and multifunctionality.

 

In a new paper published in Light: Science & Applications, a team of scientists, led by Professor Zheng You from the Department of Precision Instrument, Tsinghua University, China, and co-workers including collaborators from Huazhong University of Science and Technology and Beijing Information Science and Technology University, have developed a dual-mode beam forming device that synergizes tunable hybrid cascaded metasurfaces with a shape memory alloy micro-actuator. This innovation bridges the advantages of beam array scanning and flash LiDAR technologies. Based on this platform, they designed a reconfigurable optical system capable of dynamically switching between high-resolution scanning and single-shot full-field illumination modes. Compared to state-of-the-art solutions, this technology delivers superior balance between resolution, field of view, and adaptability, enabling high-precision detection across diverse applications. The reported methodology paves the way for next-generation LiDAR systems, autonomous navigation, and advanced 3D sensing without compromising performance versatility.

 

The hybrid cascaded metasurfaces integrate an input polarization-sensitive Pancharatnam-Berry phase metasurface and an output polarization-insensitive propagation phase metasurface, enabling simultaneous projection of scanning beam arrays and uniform flash illumination through incident polarization modulation. In scanning mode, the micro-actuator laterally shifts the output metasurface (±100 μm) to project a beam array covering a wide ±35° field of view with tunable angular resolution, achieving unprecedented flexibility. In flash mode, the system illuminates and detects entire target scenes uniformly in a single exposure.

 

Based on this device, the team established an adaptive 3D reconstruction scheme to implement a dual-mode LiDAR system. The system first utilizes the flash illumination mode to perform snapshot 3D detection, capturing target edge morphology. This initial scan provides the critical basis for intelligently selecting translation steps during the subsequent beam array scanning mode. During beam scanning, the system dynamically executes coarse or fine scans tailored to specific objects of interest. Remarkably, in fine scanning mode with a 10 μm translational step, the angular resolution for 3D point cloud construction reaches ~0.3°, while maintaining a depth error below 1.02% for complex objects.

 

This dual-mode LiDAR uniquely merges the high precision and long range of beam scanning systems with the high efficiency of flash LiDAR, significantly enhancing adaptability. Furthermore, by leveraging the ultrathin, multifunctional nature of metasurfaces, the researchers achieved a compact, tunable beam forming device compatible with arbitrary detection mechanisms—including time-of-flight and binocular vision. The team emphasizes that their work establishes a foundational framework for high-performance optical sensing devices, advancing not only LiDAR miniaturization but also boosting detection versatility.

 

When Left-Circularly Polarized (LCP) light illuminates the tunable hybrid cascaded metasurfaces, the system operates in beam array scanning mode, enabling high-precision 3D scanning with tunable resolution. Conversely, Right-Circularly Polarized (RCP) light activation switches the device to flash illuminating mode, achieving instantaneous full-field snapshot detection.

 

The beam-forming device features a polarization-sensitive geometric-phase input metasurface (arrayed design) for beam convergence/divergence, cascaded with a polarization-insensitive output metasurface employing propagation phase control. Precise lateral translation between metasurface layers is driven by a shape memory alloy micro-actuator enabling dynamic beam scanning in beam array scanning mode.

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