近红外偏振无关超透镜研究

Research on near-infrared polarization-independent metalens

  • 摘要: 基于微纳结构对光波调控实现聚焦与成像的超透镜是目前国际上竞相发展的前沿技术。本文针对目前已报道的近红外超透镜偏振相关、系统复杂以及透过率低等难题,提出了一种偏振无关的近红外超透镜。以低折射率材料SiO2为基底,高折射率材料Si圆形柱为相位调控单元,设计波长为1.31 μm。利用时域有限差分方法分析了近红外超透镜构建单元的光波调控特性,构建了构建单元的相位延迟特性曲线,探究了构建单元周期对光波透过率的影响规律,实现了构建单元的优化设计,并基于波前重构方程,设计出偏振无关的近红外超透镜。数值仿真结果表明:相位调控单元的相位延迟与透过率不仅取决于Si圆形柱半径、高度,而且与单元周期密切相关;基于分析的构建单元光波调控特性,设计的近红外偏振无关超透镜焦距仿真值为19 μm,与设计值较好吻合,透镜透过率达到65%。设计的超透镜不仅体积小、质量轻,而且为平面透镜,因此易于光学系统集成,在激光雷达、激光夜视等技术中展现出广阔的应用前景。

     

    Abstract: 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.

     

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