Active Metasurface Absorber for Intensity- Dependent Surface-Wave Shielding

A novel intensity-dependent metasurface absorber for continuous surface waves is presented, which is composed of electrically tunable unit cells controlled by a centralized active module. p-i-n diodes are embedded in the unit cells, functioning as rheostats for both the dispersion tuning and dissipation adjustment. The module fulfills the nonlinearity by sensing incoming wave intensities and offering direct-current (dc) signals to control the absorptive array. Due to the centralized control, the cells operate in good consistency, which is beneficial for a wide frequency band and absorption range. A prototype is fabricated and measured, and its strong intensity-dependent absorption is demonstrated. When the incident power level increases, the absorptance is enhanced gradually from 19.4% to 92.7%. In an instantaneous bandwidth of 12.0%, the absorption can be tuned from 30% to 80% by changing the power. Furthermore, the dynamic range of power and absorption range can be flexibly customized as required, and the nonlinear functions can be promptly turned off if necessary, showing the advantages of the active mechanism. Such results enable the metasurface to be useful in electromagnetic (EM) shielding to mitigate the harmful impact of strong surface waves and protect small useful signals.