徑向極化光聚焦之金屬表面電漿激發研究

Abstract

利用高NA的物鏡將radial polarization的極化光聚焦在金屬表面，可以在每個徑向方向都產生表面電漿波，藉由建設性干涉， 表面電漿波會在中心而產生一個次波長的聚焦點，而在反射的出光面會產生一個暗圈，而此暗圈的產生是因為光被耦合到金屬表面激發表面電漿波。事實上我們可以把此金屬結構看成一個角度的濾波器，只讓產生表面電漿波的角度的光通過，因此聚焦面的光場由激發表面電漿的入射光所貢獻。 在此篇論文中，首先會討論如何改變結構去找出適當的參數去激發表面電漿，之後會利用近場實驗以及模擬去討論不同極化光的聚焦場型，最後再證實當表面電漿發生時，金屬膜確實可以看成一個空間角頻率濾波器，讓特定激發表面電漿波的空間角頻率通過。

The radial polarized light focused on the metal surface with high NA system could generate the Omni- directional surface plasmons. Constructive interference of SPP lead to a sub wavelength focused spot. Besides, a dark ring appeared at the exit pupil because the light is coupled to metal surface to excite the SPP. Actually, the metallic layer could be regarded as an angular filter which enables the light with excitation of SPP to pass. Therefore, these incident lights contribute to the total focused field. In this thesis, I will discuss how to find the proper conditions to excite the surface Plasmon with different structure. In the following, the focused field of the different polarization will be investigated by simulation and experiment. Finally, I will verify that a metallic layer could be regard as an angular filter with the occurrence of surface Plasmon.