Research on near-infrared polarization-independent metalens

The metalens based on the micro-nano structure to achieve the focusing and imaging of the lightwave regulation is a front technology currently competing in international development. Aiming at the problems of near-infrared metalens polarization dependence, system complexity and low transmittance that had been reported, a near-infrared polarization-independent metalens was proposed. The low refractive index material SiO₂ was used as the basement, the high refractive index material Si cylinder was used as the phase control unit, and the designed wavelength was 1.31 μm. The finite-difference time-domain method was used to analyze the lightwave regulation characteristics of the near-infrared metalens building unit, and the phase delay characteristic curve of the building unit was constructed. The influence law of the building unit period on the lightwave transmittance was discussed, the optimization design of the building unit was realized, and based on the wavefront reconstruction equation, the near-infrared polarization-independent metalens was designed. The numerical simulation results show that the phase delay and transmittance of the phase control unit are not only dependent on the radius and height of the Si cylinder, but also closely related to the unit period. Based on the analysis of the lightwave regulation characteristics for the building unit, the simulated focal length of the designed near-infrared polarization-independent metalens is 19 μm, which is in good agreement with the designed value, and the lens transmittance reaches 65%. The designed metalens is not only small in size, light in weight, but also is a plane lens. Therefore, it is easy to integrate the optical system, and it has broad application prospects in laser radar, laser night vision and other technologies.