Abstract In this paper, we present a Gaussian to tophat beam shaper (GTBS) based on an all-dielectric metasurface lens for sub terahertz (sub-THz) applications. In order to calculate the required phase profile of the GTBS, we use an analytical procedure based on the geometrical transformation technique. The calculated phase profile is then realized by a silicon (Si) metasurface lens consisting of rectangular-shaped pillars of subwavelength dimensions. Because of large solution domain relative to the operation wavelength, we combined the beam envelope and the finite element methods to simulate the structure with a high precision. By designing an anti-reflection metasurface made up of periodically arranged Si pillars of subwavelength dimensions at the back surface of the beam shaper, we reduced the reflection from the lens surface considerably. The proposed idea is firstly investigated in a two-dimensional (2D) structure composed of an array grooves in a Si substrate and then is extended to three dimensions (3D) by considering a 2D array of subwavelength pillars or holes. The 3D structure is shown to be polarization insensitive. The compactness, ease of fabrication, low transmission loss, polarization independence, and straightforward design of the proposed metasurface beam shaper lens make it a promising choice for the implementation of sub-THz quasi-optical elements especially for standoff imaging systems.

中文翻译：

---

用于亚太赫兹范围内高斯到顶帽光束整形的紧凑型偏振不敏感全介电超表面透镜

摘要 在本文中，我们提出了一种基于全介电超表面透镜的高斯到顶帽光束整形器 (GTBS)，用于亚太赫兹 (sub-THz) 应用。为了计算所需的 GTBS 相剖面，我们使用基于几何变换技术的分析程序。然后通过由亚波长尺寸的矩形柱组成的硅 (Si) 超表面透镜实现计算出的相位轮廓。由于相对于工作波长的解域较大，我们结合光束包络和有限元方法来高精度地模拟结构。通过在光束整形器的后表面设计由周期性排列的亚波长尺寸的硅柱组成的抗反射超表面，我们大大减少了来自透镜表面的反射。所提出的想法首先在由硅衬底中的阵列凹槽组成的二维 (2D) 结构中进行研究，然后通过考虑亚波长柱或孔的二维阵列将其扩展到三维 (3D)。3D 结构显示为对偏振不敏感。所提出的超表面光束整形器透镜的紧凑性、易于制造、低传输损耗、偏振独立性和简单的设计使其成为实现亚太赫兹准光学元件的有希望的选择，特别是对于间隔成像系统。