全介電幾何相位超穎表面的 抗反射設計;Design anti-reflection for all-dielectric geometric phase metasurface

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/88182

Title:	全介電幾何相位超穎表面的抗反射設計;Design anti-reflection for all-dielectric geometric phase metasurface
Authors:	廖育萱;Liao, Yu-Hsuan
Contributors:	光電科學與工程學系
Keywords:	超穎介面;metasurface
Date:	2022-01-17
Issue Date:	2022-07-13 18:27:02 (UTC+8)
Publisher:	國立中央大學
Abstract:	本論文將PB-phase之超穎介面的應用簡化為半波板模型，探討將奈米鰭與抗反射層(MgF2)結合後之光學特性及總偏振轉效率(Overall PCE)。當抗反射層為平坦的薄膜結構時，對效率上提升是無貢獻，因此抗反射層需與奈米鰭相同具有結構異向性，將抗反射層置於奈米鰭頂部時，其Overall PCE提升會較穩定。在GaN奈米鰭情況下，當MgF2從0 nm增加到160 nm時，Overall PCE可從53.18% 提升至55.06%，提高1.88%，但因為GaN材料於可見光範圍下會有吸收的損耗，導致效率提升會較困難。使用Nb2O5奈米鰭時，其折射率適中且無吸收特性，相較於GaN其Overall PCE高於1.7倍，加入MgF2後，Overall PCE從92.38%提升至94.58%，可提升2.2%。;In this thesis, the optical properties and polarization conversion efficiency (P.C.E) has been investigated by combining the anti-reflection layer (MgF2) with the nano-fin. In order to obtain the highest P.C.E, the height of the nano-fin has been considered as a half-wave plate. We numerically demonstrated that a flat anti-reflection film shows no contribution to efficiency improvement. The structural heterogeneity is necessary for the anti-reflection. Moreover, the overall P.C.E can be enhanced more stably when MgF2 stacked on the top of nano-fin. In the case of the GaN nano-fin, the overall P.C.E is enhance from 53.18% to 55.06% when the height of MgF2 is increased from 0 nm to 160 nm. On the other hand, it is a challenge to enhance the efficiency of GaN based nano-fin due to the absorption loss in the visible light range. Therefore, we numerically investigated the materials that do not suffer from absorption loss in the visible light. Among them, niobium oxide (Nb2O5) becomes a good option because of the fair refractive index and no absorption. In comparison with GaN nano-fin, the overall PCE of Nb2O5 nano-fin is 1.7 times higher. The highest overall P.C.E enhances from 92.38% to 94.58% when MgF2 stacked on the top.
Appears in Collections:	[Graduate Institute of Optics and Photonics] Electronic Thesis & Dissertation

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