兆赫波波段之微共振腔研究

Abstract

本論文是研究操作在兆赫波波段中，金屬-介電質-金屬型微共振腔陣列的特性與物理機制。我們設計光柵型、方塊型、圓形以及六角形四種不同金屬圖案的微共振腔，並研究介電質厚度對微共振腔光學特性的影響。透過觀察微共振腔的反射率頻譜，我們發現一維光柵型共振腔的共振頻率隨介電質厚度增加會發生紅移或藍移的現象，與表面電漿子耦合強弱以及共振腔束縛電場的能力有關。而最大的共振吸收強度只會在某一特定介電質厚度出現，此厚度的值會受到微共振腔大小與週期影響。二維微共振腔較一維微共振腔有較佳的共振腔吸收強度與品質因子。其中，圓形微共振腔有最高的品質因子，而六角形微共振腔有最強的共振吸收。

This thesis studies the characteristics of metal-dielectric-metal type microcavities arranged in array configuration and the underlying physics in the terahertz regime. We design four types of microcavities in grating, square, circle and hexagonal shapes and study the influence of dielectric thicknesses on the optical properties of each type of microcavities. For grating-type microcavities, we find that the resonance frequencies appear redshift or blueshift as dielectric thickness increases. The phenomenon is related to the coupling strength between surface plasmon polaritons and the confinement strength of electromagnetic waves in microcavities. We find that the peak resonant absorption only appears at a specific dielectric thickness, which is determined by the size and periodicity of microcavities. On the other hand, the two-dimensional microcavities have much better absorption intensity and quality factor. Among the two-dimensional microcavities, circular-type microcavities have the highest quality factor while hexagonal-type microcavities have the strongest resonant absorption.