金屬孔洞陣列造成增強性兆赫輻射穿透時孔洞內介質的效應

Abstract

二維週期次波長孔洞陣列的金屬薄板(2D-MHA)可以在某些特定的兆赫頻率(THz)造成異常高的穿透，這種增強性的穿透被認為是由於入射光與在金屬與介電質之間的表面電漿極化子(SPP)發生了共振耦合。我們利用實驗與模擬研究2D-MHA中洞裡介質在穿透特性中的角色，發現當洞裡填入介電質材料時有新的現象產生，當洞裡填入UV膠時，兆赫波的穿透特徵與2D-MHA的厚度有強烈的相關，且改變2D-MHA週遭介質的穿透特質也和以往不同；當孔洞深度較深時，SPP展現出兩種不同的模態 (耦合與非耦合)，這也在利用時域有限差分法(FDTD)的電場模擬結果中獲得確認。

Metal plates perforated with two-dimensional periodic arrays of sub-wavelength holes (2D-MHAs) exhibit high transmission at selective terahertz frequencies. This mechanism of the enhanced transmission characteristic is usually attributed to the resonant coupling between the incident light and surface plasmon-polaritons (SPPs) which are located at the metal-dielectric surfaces. We experimentally and numerically investigate the role of material in the holes on transmission characteristics of the 2D-MHA. New phenomena, however, appear when holes of the 2D-MHA are filled with dielectric material. We find distinctive THz transmission characteristics depending on the thickness and properties of the adjacent medium for the 2D-MHA of which holes are filled with UV-gel. For deeper holes, SPP can exhibit two distinct modes, coupled and uncoupled types as confirmed in the simulated results for the electric field using finite-difference time-domain (FDTD) algorithm.