基於平面光學元件的快速發展，由次波長奈米結構陣列而成的超穎介面至今已存在多種光學應用，因其具備對電磁波物理特性的精準調控能力，備具發展潛力而受到重視，如一般的反射式超穎介面藉由結構設計可實現對圓偏振光的偏振轉換的功能，本文所設計之非厄米電漿子超穎介面，引入非厄米系統中，因奇異點(Exceptional Point, EP)存在所產生的單向傳輸特性，設計於特徵波長與特定尺寸下，可選擇性吸收左圓偏振光使轉換至正交偏振態之反射效率為零，實現單一偏振轉換特性的反射式超穎介面，透過分析反射矩陣之特徵值驗證奇異點的存在，並透過實驗驗證單向反射的特性，可於EP波長下達到43%的圓二色性。
本研究所設計之非厄米電漿子超穎介面，藉由幾何相位(Geometric phase)的排列方式，設計光束偏轉超穎介面，將其因EP存在所產生之單向反射特性引入波前調控，於圓偏振光入射下可實現非對稱異常反射效果。實際樣品於特徵波長與其他波長下可形成鮮明對比，在可見光波段下實現光束偏轉效果外，於特徵波長下僅會有被轉換為左圓偏振態的正一階光束出射。進一步以x偏振光正向入射，檢測是否對線偏振光也具備相同的非對稱偏折分光功能，因一般各向異性結構所構成之光束偏轉介面在x偏振光入射下，將其偏折為兩道對稱的正交圓偏振光束出射。而此非厄米光束偏轉超穎介面在特徵波長下可以實現非對稱光束偏轉效果，於x偏振光正向入射下僅有右圓偏振分量被轉換為左圓偏振光出射。
後續針對此對掌性金屬奈米結構，於材料折射率改變後，重新優化一組鏡像單元結構，在數值模擬與實驗結果中驗證其因結構鏡像對稱而相反的光學響應，並結合單層過渡金屬硫化物(TMDCs)作為螢光光源設計單元結構，透過非厄米電漿子超穎介面的圓二色性，在單層二硫化鎢(WS2)的螢光波長下，實現對螢光偏振度調控的功能。期望後續能結合大面積單層二維材料與非厄米光束偏轉超穎介面，藉由侷域性表面電漿共振與激子交互作用，進一步實現非同調光源的非對稱光束偏轉效果。

Non-Hermitian metasurfaces can exhibit distinctive and unconventional optical behaviors driven by the interaction of gain and loss, which give rise to phenomena such as anomalous reflection, nonreciprocal transmission, and sensitivity enhancement.
Here, we numerically designed and experimentally demonstrated a plasmonic non-Hermitian metasurface which consists of 2D planar chiral meta-structure arrays working at an exceptional point (EP). Through the optimization of the meta-atoms, our results indicate that at the positions of optical singularities, the reflection intensities of light with polarization states parallel to the incident light approach zero. This observation verifies that the utilization of plasmonic topological metasurface units in metasurface devices can effectively disrupt optical symmetry. By resolving the eigenstates and eigenvalues of the reflection matrix, we validate that the parameter space forms a self-intersecting Riemann sheet in which the EP is located at the point of intersection.
Moreover, by introducing Pancharatnam-Berry (PB) phase, the EP-enabled non-Hermitian phase gradient metasurface can control circularly-polarized reflected beams independently under linearly and circularly polarized light illumination at different wavelengths, each with distinct power ratios.
Furthermore, we designed a pair of mirrors symmetrical non-Hermitian metasurfaces to realize the opposite optical response. By incorporating with monolayer TMDCs, the emitted photons could strongly couple with the non-Hermitian metasurface, leading to the asymmetric polarization state in emitted photons in the far field.

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