透過超穎介面設計的半波板運用在可調控的光學Tamm能態

Abstract

光學Tamm state 是一種電漿共振發生在光子晶體表面與金屬薄膜 之間的一種侷域的表面模態。在這篇論文中，我們是第一個利用膽固 醇液晶和反射式的超穎介面在模擬和實驗中都可以觀察到光學的 Tamm state。一般常見的光學Tamm state 主要是發生在布拉格反射 器和金屬薄膜之間，藉由改變DBR 上層薄膜的厚度或是製作DBR 孔洞 陣列，可以用來調控模態的共振波長。但是在樣品製作完之後，很難 藉由控制薄膜的品質或是調整DBR 的厚度去作調控，因此光子液晶 (CLC)被提出來當作替代DBR 去調控光學Tamm state 共振波長的材 料。但是表面模態並不能直接在光子液晶和金屬薄膜之間激發，所以 類似半波板的反射式超穎介面被設計來當作相位和偏振上的匹配。而 且在光子液晶和超穎介面之間，可以觀察到很強的侷域電場和共振。 另外在光學Tamm state 共振波長的調控上，可以藉由改變光子液晶 的溫度或是光學的止帶去達到一個寬頻的可調控性。

Optical Tamm state is a localized surface mode that plamonic resonance occurred at the boundary between a photonic crystal and metal. We demonstrate, both simulation and experiment, the first observation of optical Tamm state formed by cholesteric liquid crystal (CLC) and reflected metasurface. Conventional optical Tamm states have been investigated at the interface of distributed Bragg reflector (DBR) and metal. By varying the thickness of the top layer of DBR or making DBR porous, it could possibly tune the resonance wavelengths. However, it is very difficult to control the quality or modify the thickness of DBR after a sample is fabricated. Therefore, photonic liquid crystal called CLC is proposed to substitute the DBR to achieve the tunability of the resonance wavelength of the optical Tamm state, but the surface state cannot be excited directly with a photonic liquid crystal and flat metal films. The novel design of metasurfaces as reflective half-wave plates provides phase and polarization matching. At the interface between a photonic liquid crystal and a metasurface, a strong localized electric field and sharp resonance are observed. In this work, the spin selective optical Tamm states has been accomplished. The resonance wavelength of optical Tamm states can be controlled by varying the temperature of the liquid crystal to achieve wide-range tunability.