單色可見光波段無偏振選擇全介電質超穎透鏡

Abstract

利用次波長的結構所設計出二維的超穎介面，這樣做出來的超穎透鏡可達到非常輕薄的特性，體積也非常之小，而利用超穎介面的特性能使產生出來的波前可以為均勻的平面波，而在本論文當中，我設計出一種無偏振的超穎透鏡，跳脫出以前利用PB-Phase所設計的概念，利用不一樣的結構變化，找出擁有2π相位延遲的特性，進而做出無偏振選擇的超穎透鏡。 而在本論文當中，利用單晶矽以及氮化鎵這兩種介電質的材料，來完成無偏振超穎透鏡的材料轉換，並且在本論文當中也利用了市面上的軟體CST來進行模擬的結果，將模擬出來的相位延遲可做出相對應的相位分佈，完成我們的無偏振超穎透鏡。利用我們實驗室的 Elionex e-beam 7000 畫出我們的結構圖案並利用ICP機台蝕刻我們的介電質材料，達到預期的介電質高度。 在本論文當中也利用偏振片的轉動，檢測出本論文的原件-無偏振超穎透鏡的極化敏感度，最值得一提的事，在本論文當中的無偏振超穎透鏡擁有高達90%以上的高效率表現。

Ultrathin, flat optical devices of high performance can be achieved by using metasurfaces that are typically constructed of artificial patterns of subwavelength depth. Metasurfaces can be designed to generate symmetrical wave front where the term, metalenses, has been widely used. In this study, we have introduced a new design principle to develop metalenses without polarization selection instead of using the Pancharatnam-Berry phase design concept. Dielectric materials, GaN and Silicon, have been chosen to realize our metalenses without polarization selection. A commercial software, CST, has been utilized to achieve the phase retardation distribution of the metalenses by simulating the behavior of light-matter interaction for each subwavelength building block. The metalenses have been fabricated by employing the Elionex e-beam 7000 lithography equipment and the ICP system. The polarization insensitivity of the metalenses has been inspected in this study as well. Moreover, it is worth noting that the measured focusing efficiency of our polarization-insensitive metalenses is as high as 90% or higher.