高穿透率高品質因子可切換太赫茲雙層超表面

Abstract

本論文致力於設計同時具有高穿透率與高品質因子，且體積微小並具有高度整合的太赫茲雙層超表面元件。首先，利用全波段電磁模擬，並利用可撓曲的Kapton及SU8聚合物為基板，設計可撓曲高穿透的Au / SU8 / Au的太赫茲超表面結構。根據改變兩層Au超表面的色散關係以及SU8介電質層厚度，達成高穿透率所需滿足的相位關係。此外，改變超表面的幾何設計可使元件的操作頻率帶寬由單一帶寬調整為雙帶寬或者寬帶寬。第二，我們發現藉由改變兩層超表面各自的共振性質與介電質層的光學特性，除了實現高穿透率以外，可進而操控穿透頻譜的線型與線寬。因此，以操作頻率為單一帶寬的超表面作為基礎，我們成功設計出具高穿透率，且高品質因子的太赫茲雙層超表面。第三，我們將相變材料整合在太赫茲雙層超表面結構中，並藉由改變溫度或外加電壓使相變材料發生相變，進而實現主動切換超表面的穿透性質，使其具有調制太赫茲光的能力。本論文中所設計的太赫茲雙層超表面具有廣泛應用，可作為未來高速太赫茲無線通訊中所需的窄頻帶帶通濾波器以及太赫茲光調制器，或者作為具有高靈敏度的生物與化學分子感測器，亦可應用於研究低維度半導體量子結構中光物質強耦合的物理現象。This thesis is focused on the design of novel terahertz (THz) bilayer metasurfaces, featuring high transmission, high quality factor, small footprint, and facile integrability. First, we design using full-wave simulations highly transmissive Au/SU8/Au flexible THz bilayer metasurfaces based on Kapton and SU8 polymer substrate. The phase requirement for high transmission is satisfied by tailoring the dispersion of both Au metasurfaces and the thickness of the SU8 dielectric layer. The THz bilayer metasurfaces can operate for single band, dual-band, and broadband through changing the metasurface design. Second, we discover that both the line shape and the line width of the transmission passband of the THz bilayer metasurfaces can be controlled and manipulated by altering the resonant characteristics of two metasurface layers and the optical properties of the dielectric spacer. We thus successfully design a new class of THz bilayer metasurfaces, possessing simultaneously a high transmission efficiency and a high quality factor. Third, we integrate phase change materials into the THz bilayer metausrface structure to realize actively switchable transmission through phase transition induced by temperature change or external bias, suitable for THz light modulation. The designed THz bilayer metasurfaces can be of use for a wide range of practical applications, including high-speed wireless communications, highly sensitive biological and chemical detection, and the investigation of strong light-matter coupling in low-dimensional semiconductor quantum structures.