反射型光变色超表面滤光结构

Reflective Metasurface Filter with Optical Variable Color

提出了一种反射型超表面滤光结构,该滤光结构由基底、低折射率纳米光栅、Ag光栅、SiNx高折射率介质层组成。理论模拟结果表明:45°入射角下,在垂直于光栅栅线的入射平面内,反射谱峰值出现在475 nm波长处;在平行于光栅栅线的入射平面内,反射谱峰值出现在550 nm波长处。其电场分布特性表明,在不同的平面内TE偏振入射光激发的导模共振区域不同,TM偏振下激发的导膜共振强度与表面等离子体共振强度不同,导致该结构在垂直于光栅栅线方向与平行于光栅栅线方向的两个平面内表现出两种截然不同的颜色。基于此制备的超表面结构样品不但光变色效果明显,且易于与纳米压印工艺相结合实现大幅面光变色结构制备,在防伪和图案信息编码等领域有广阔的应用前景。

A reflective metasurface filter is proposed in this paper, which consists of a substrate, a nanograting with low refractive index, a Ag grating and a high-refractive-index dielectric SiN;layer. The simulation results show that with the incident angle of 45°, the reflection peak appears at the wavelength of 475 nm for the plane perpendicular to the grating line, while it is located at 550 nm for the plane parallel to the grating line. The electric field distribution characteristics demonstrate that for different incident planes, transverse electric field-polarized incidence excites guided-mode resonance in different areas, and the intensity of guided-mode resonance is different from that of surface plasmon resonance in the case of transverse magnetic field-polarized incidence. As a result, different colors are present in the two planes perpendicular to and parallel to the grating line, respectively. Accordingly, the fabricated metasurface sample has significantly optical variable color, which can be flexibly realized for large-area structures by nanoimprint lithography. The proposed reflective metasurface filter has a broad application prospect in the fields of anti-counterfeiting and information encoding.