Multi-band coherent perfect absorption excited by a multi-sized and multilayer metasurface

We propose a multi-band infrared coherent perfect absorber where four perfect absorption peaks can be obtained for antisymmetrical inputs. The FWHM is nearly four times larger than that of a single band absorber. In addition, the absorptivity of each peak can be independently tuned by phase modulation. Since only magnetic resonances in the form of catenary optical fields in the upper and lower dielectric layers can be excited for symmetrical inputs. the number of absorption peaks will be reduced by half at this time. The absorption frequency under symmetrical inputs can be flexibly selected from low frequency to high frequency by changing the material of the upper and lower dielectric layers. Moreover, the bandwidth in optimized broadband absorber is enhanced by 9 times while high absorbance is maintained. The characteristic of the enhancing absorption bandwidth and the selective absorption may allow our metasurface to be used in many applications such as optical switch and modulators. (C) 2018 The Japan Society of Applied Physics