A method of metasurface collimating pulsed laser diode for lidar emission system

Metasurfaces can overcome the shortcomings of traditional lenses, such as large volume, heavy weight and difficult aberration correction. However, based on the diffraction principle, metasurfaces have serious chromatic aberration and lower efficiency than traditional glass lenses, so they need to be used with monochromatic laser illumination. Therefore, metasurfaces are the best choice for lidar systems to realize miniaturization and lightweight design. The lidar emitting system usually uses a 905nm pulsed laser diode (PLD) as the light source, which requires two cylindrical lenses to collimate the laser beam in the X and Y directions separately. In this paper, two metasurfaces is designed in different areas of the same substrate to collimate the laser beam. By folding the light path through the right-angle prism, the beam passes through two metasurfaces successively, which are responsible for collimating the rays in the X and Y directions respectively. After collimation, the divergence angles of the rays are less than 0.3°×0.1°. By attaching a microelectro-mechanical system (MEMS) mirror behind the metasurfaces to realize scanning, we can obtain the lidar emitting system. By using metasurfaces to replace the traditional cylindrical lenses, the weight and size of the lidar emitting system can be greatly reduced. With further research on metasurface technology, metasurfaces are expected to replace the traditional lenses and even the scanning device in lidar, so as to realize highly integrated chip-level lidar.