The mid-infrared radiative properties of microscale simple and complex heavily doped silicon gratings were studied with the finite-difference time-domain method, and the feasibility of using complex grating for mid-infrared wavelength-selective surfaces was investigated. The results show that for the simple gratings, there exist the sharp peaks in different filling ratios. The sharp peak observed with filling ratio 0.4 is much higher than that of filling ratio 0.1. Furthermore, the location of absorptance peak shifts to the longer wavelength with the increase of grating period. When the carrier concentration increases, the peak location shifts towards shorter wavelength and the FWHM (Full-width at half-maximum) reduces. For the complex gratings, although the absorptance peak is lower than that of the simple grating, the full width at half maximum is much larger, which comes from the excitation of surface plasmon polaritons. The complex grating shows better performance than the simple grating as the wavelength-selective surface.%利用时域有限差分法对中红外波段微尺度重掺杂硅简易光栅和复杂光栅的光谱吸收率进行数值模拟,验证重掺杂硅复杂光栅作为波长选择性吸收表面的可行性.计算结果表明;对于简易光栅,不同填充比条件下的光谱吸收率曲线均存在峰值,其中填充比为0.4的吸收率峰值远高于填充比为0.1的峰值;随着光栅周期的增大,吸收率峰值位置向长波长波段移动;当掺杂浓度增加时,吸收率峰值位置移向短波长波段并且半峰全宽值有所减小.对于复杂光栅,与简易光栅相比虽然吸收率峰值有所降低,但其半峰全宽明显比简易光栅的大,主要来源于表面等离子体激元的激发.作为波长选择性吸收表面,复杂光栅表现出比简易光栅更优良的性能.
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