金屬光柵在不同偏振下穿透機制之研究

Abstract

我們分析了金屬光柵在不同偏振光入射下的穿透頻譜及近場場型，我們除了研究此系統的共振穿透外，另外更探討雷利波長下不同偏振光的穿透機制，入射光會激發表面的駐波，對於P-波(TM)，駐波會導致金屬表面電荷重新分布進而使得入射光無法穿透，對於S-波(TE)而言，駐波會與入射波產生建設性干涉並出現穿透峰值。而模擬也與實驗結果一致。 此外，我們觀察到金屬光柵上會有Fabry-Perot模態導致的穿透峰值，透過此模態，我們能針對不同偏振光設計出光學濾波器。

We analyze transmission characteristics and near-field patterns of metallic gratings at different polarizations. We not only study the resonance transmission, but also focus on the transmission mechanism at Rayleigh wavelength where the standing wave is excited by incident wave. For P-polarization (TM), the standing wave causes surface charge redistribution, which results in null transmission. However, for S-polarization (TE), the constructive interference between incident wave and standing wave leads to high transmission. The calculation results are in good agreement with experiments. We show that the metallic gratings can be designed as optical filters for different polarizations by tuning the resonance wavelength of Fabry-Perot mode.