裂環共振器超穎介面之光操控與應用

Abstract

超穎介面是由一種經妥善排列後的人造次波長金屬結構所構成，並具有自然界中不存在且特殊的光操控能力。超穎介面的光操控能力是由組成的奈米結構之幾何參數與週期排列方式所決定，本論文利用此特性設計兩種不同形式的裂環共振器超穎介面，並分析其光操控能力與暗場之應用。 第一種是由直立式裂環共振器構成的超穎介面，比傳統的平面奈米柱超穎介面多了一個維度可以進行操控。直立式裂環共振器超穎介面具有將光通訊波段的入射光異常反射到特定角度的能力，藉由模擬分析，此超穎介面具有很高的指向性與訊雜比。比起傳統奈米柱超穎介面，直立式裂環共振器超穎介面能解省將近百分之五十的佔據表面積，提升超穎介面之積體光學元件的密度。 第二種超穎介面是由非對稱裂環共振器陣列所構成，此超穎介面在暗場下擁有陣列邊界發光的特性，藉由增加非對稱裂環共振器的週期，邊界發光特性會變成全陣列的發光。此非對稱裂環共振器超穎介面是第一個設計在暗場下工作的超穎介面，在未來能應用在暗場下的細胞捕獲器或暗場下的光陷阱。

Metasurface is a kind of artificial material constructed by metal nanostructure with well-designed patterned on its surfaces has shown to possess unusual abilities to manipulate light. In this dissertation, two types of split-ring resonators based metasurface have been designed and investigated. Recently, we have designed the 3D nanostructures, namely vertical split-ring resonators (VSRRs), which opens up another degree of freedom in the metasurface design. VSRR-based metasurface is able to anomalous steering reflection of a wide range of angles can be accomplished with high extinction ratio using the finite-difference-time-domain simulation. On the other hand, VSRR-based metasurface can be made with roughly half of the footprint compared to that of rods-based metasurface, enabling high density integration of metal nanostructures. At present, proposed functions of metasurface-based devices are mostly oriented to bright-field but not dark-field. We first propose and analyze an asymmetric split-ring-based metasurface with ability of edge-emission at visible region under dark-field environment. By changing periodic distance between two adjacent split-ring elements, the mode with edge-emission can be controlled. It can be observed under dark-field measurement with property of spectral-dependent spatial variation. The feasibility of proposed design has been demonstrated by the electromagnetic numerical simulation and dark-field measurement. The broadband phenomena of edge emission have been observed from 650 to 900 nm.