基于交替光栅和石墨烯设计了一种近红外波段电磁超材料多通道吸收器。采用时域有限差分法(FDTD)数值模拟了结构设计参数对吸收光谱的影响规律,获得了最佳结构。同时探究了各通道吸收率对入射光源角度的依赖性。仿真结果表明,基于法布里-珀罗(F-P)腔共振、磁激元共振和相消干涉形成的吸收光谱主要集中在0.95~1.15 μm近红外波段。交替光栅的结构参数和介质层厚度对光谱特性影响较大,当光栅高度增大或周期减小时,腔共振模迅速右移,并伴随各干涉峰小幅度右漂,吸收率大幅改变;介质层厚度对干涉谱影响强烈,当介质层厚度达40 nm以上时,干涉谱几乎消失。各通道吸收峰对光源入射角不敏感,但当入射角在10°以上时,低端吸收率随入射角线性增大,线性拟合度高达0.9931。

An electromagnetic metamaterial multi-channel absorber is designed based on alternating grating and graphene. The influences of structural design parameters on absorption spectra is numerically simulated using the finite-difference time-domain (FDTD) and the optimal structure is obtained. At the same time, the dependence of the absorptivity at each channel on the angle of the incident light source is investigated. The simulation results show that the absorption spectra based on F-P cavity resonance, magnetic exaction resonance, and destructive interference are mainly concentrated in the 0.95-1.15 μm near-infrared band. The structural parameters of the alternating grating and the thickness of the dielectric layer have a great impact on the spectral characteristics. As the grating height increases or the period decreases, the cavity resonance mode shifts rapidly to the right, and the interference peaks shift slightly to the right, and the absorption rate changes greatly. The thickness of the dielectric layer has a great influence on the interference spectrum, and the interference spectrum almost disappears when the thickness is larger than 40 nm. The absorption peak at each channel is not sensitive to the incident angle of the light source, but when the incident angle is over 10°, the low-end absorptivity increases linearly with the incident angle and the linear fitting degree is up to 0.9931.