Multi-Frequency Perfect Absorption by Ultra-Thin Time-Modulated Metasurfaces

Here, we study the interference phenomena produced in time-modulated metasurfaces when they are illuminated by multiple harmonics opening a new paradigm of coherent time-modulated metasurfaces. In particular, we obtain perfect absorption at multiple frequencies by inducing slow time modulation of a resistive sheet. Also, it will be shown that it is possible to fully tune the absorption by properly designing the modulation parameters.