Adaptively Switching Between Amplification and Absorption by an Intelligent Omni‐Metasurface With Nonlinear Spectral Singularity

Abstract Lasing effects at spectral singularities, along with coherent perfect absorption enable by their time‐reversal symmetry, pave the way for achieving high‐contrast amplification and absorption within a single device. However, prior experimental realizations typically rely on laborious manual tuning of the phase difference between signal and pump waves. To address this issue, an approach is proposed and experimentally demonstrated, enabling adaptive switching between amplification and absorption at the same frequency depending on the incident intensity. This is achieved by triggering nonlinear spectral singularities in an intelligent omni‐metasurface (IOM). When the incident power exceeds the optimal communication level (≈ − 40 dBm), the system transitions automatically from a regime of linear spectral singularity—exhibiting full‐space electromagnetic (EM) wave amplification exceeding 20 dB—to a regime of coherent absorption, with attenuation as low as −8 dB. Such an adaptive behavior, arises from the nonlinear response of embedded negative differential resistance devices to incident EM waves, eliminates the need for additional manual feedback or sensing systems. Thus, the proposed IOM provides a simple and convenient means to adaptively maintain EM signal strength slightly above the optimal level (≈− 35 dBm) in wireless power and information transmission systems, enabling user‐friendly smart EM environments.