Ming Kang, Huifang Zhang, Xueqian Zhang, Quanlong Yang, Weili Zhang, Jiaguang Han
https://journals.aps.org/prapplied/accepted/b3077A50X33E621a909b163840c172b9fbca3365e
Coherent perfect absorber (CPA), a time-reversed counterpart to the laser emission, could cause all energy fed to the system to be absorbed. It can also be as an absorptive interferometer, which could provide applications in controllable optical energy transfer. Here, in order to achieve terahertz CPA, we propose a designed metasurface and experimentally demonstrate that it can serve as a polarization-insensitive CPA at one-frequency channel under normal symmetric excitation, while a transverse electric (TE) CPA at two-frequency channels around oblique 40osymmetric incidence. Such phenomena in this system can be attributed to Fano resonance consisting of interacting one bright and one dark modes under normal incidence and an additional operative dark mode under oblique symmetric excitation. The experimental results finds good agreement with the fitted coupled mode theory(CMT). Moreover, we show the output amplitude can be effectively tuned from 0 to 1 only by varying the relative phase between the two input waves. The designed CPA could find potential application in effectively controlling absorption for terahertz imaging and terahertz switches.
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