Metasurfaces are artificial optical interfaces designed to control the phase, the amplitude, and the polarization of an optical wavefront. They use physical mechanisms that rely on the coherent scattering of light by nano-scatterers of various shapes and material compositions. In this presentation, I will talk about on-chip integrations of metasurfaces, including lasers, LiDAR and detector arrays, and discuss how these innovative functionalities push the frontiers of optoelectronic systems beyond conventional devices. I will present new imaging capabilities provided by 3D LiDAR metasystem, emphasizing on the unprecedented performances achieved, in terms of frame rate, field of view and the simultaneous acquisition of multiple field of views. Finally, i will present our results on 3D insect-inspired directional imaging devices. We show that mimicking the peripheral vision of insect using planar metalens arrays, we could measure simultaneously the light coming from several directions to reconstruct 3D images. I will conclude this seminar by drawing perspectives and highlighting the opportunities that this field of research still has to offer, both from fundamental and application.
Implementation of metasurface scanning for directional beam steering and metasurface arrays on imaging sensors are used to achieved 3D light Detection and Ranging (LiDAR) with impressive imaging performances. Our works show that metasurfaces have relevant industrial applications in 3D sensing, way beyond the basic usage of metalenses for imaging or point-cloud projection.
Lidar, a technology at the heart of autonomous driving and robotic mobility, performs 3D imaging of a complex scene by measuring the time of flight of returning light pulses. Many technological challenges, including enhancement of the observation field of view (FoV), acceleration of the imaging frame rate, improvement of the ambiguity range, reduction of fabrication cost, and component size, must be simultaneously addressed so that lidar technology reaches the performance needed to strongly impact the global market. We propose an innovative solution to address the problem of wide FoV and extended unambiguous range using an acousto-optic modulator that rapidly scans a large-area metasurface deflector. We further exploit a multiplexing illumination technique traditionally deployed in the context of telecommunication theory to extend the ambiguity range and to drastically improve the signal-to-noise ratio of the measured signal. Compacting our metasurface-scanning lidar system to chip-scale dimension would open new and exciting perspectives, eventually relevant to the autonomous vehicles and robotic industries.
This work is based on the concept of integrating metasurfaces as passive elements to enhance LiDAR capabilities. We demonstrated a proof-of-concept of a LiDAR imaging system capable of acquire images at 1 million of frames per second using a faster scanner active device with a field of view up to 150°X150°. The active element redirects the light into a metasurface deflector which enhances the field of view. MHz imaging rate and 3D imaging is demonstrated. Finally, we discuss applications and limitations of using such approach, which is a strong candidate to pave the way into full autonomous vehicles.
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