多共振峰圆形光栅滤波器

提出了一种导模共振圆形光栅滤波器,以实现它在可见光范围内的多波段滤波。理论分析了圆形光栅滤波器在同一入射波偏振条件下形成多个共振峰的原因。通过微纳加工技术在硅基二氧化铪材料上实现了光栅层约为70nm的圆形光栅薄膜结构。利用一维线性光栅对圆形光栅的反射谱进行了模拟,通过角分辨微纳反射谱测试系统获得了该光栅滤波器在不同入射波偏振条件以及不同入射角时的反射谱。实验表明,在特定的光栅周期以及占空比条件下(如光栅周期350nm,占空比0.5),当线性偏振光正入射时,该圆形光栅滤波器形成了两个共振峰(505nm处和575nm处),与模拟结果基本符合。另外,光栅占空比相同时,随着光栅周期的增加,共振峰会向较长的波段偏移。实验显示:通过设计不同结构的亚波长圆形光栅,可以实现可见光范围内多个特定波段的滤波作用。

Circular grating filters with multiple resonant peaks

A guided mode resonant Circular Grating Filter (CGF) was proposed to realize its multiple band filter in the visible light regions. The reason for the formation of multiple resonance peaks in the CGF was analyzed theoretically under the polarization of the same incident beam. The freestanding CGFs with the thickness of 70 nm were realized on HfO₂-on-silicon by micro/nano machining technology. An 1D linear grating was used to simulate the reflection spectrum of the circular grating. By changing the polarization conditions and the incidence angle of incident beam, the reflection spectrum of CGF was experimentally obtained by using angular resolved micro reflectometry. Experimental results indicate that the CGF forms two resonant speaks (505 nm and 575 nm) in a specific grating period (350 nm) and a duty cycle (0.5) for the surface-normal linearly polarized incident beam. The result is in great agreement with the theoretical simulations. Furthermore, the resonance peaks will shift to longer bands with the increase of the grating period under the same duty cycle. It concludes that the filtering effect of multiple bands can be realized by designing different subwavelength gratings with different structures.