Non-linear coherent perfect absorption in the proximity of exceptional points

Coherent perfect absorption is one of the possibilities to get high absorption but typically suffers from being a resonant phenomena, i.e., efficient absorption only in a local frequency range. Additionally, if applied in high power applications, the understanding of the interplay of non-linearities and coherent perfect absorption is crucial. Here we show experimentally and theoretically the formation of non-linear coherent perfect absorption in the proximity of exceptional point degeneracies of the zeros of the scattering function. Using a microwave platform, consisting of a lossy nonlinear resonator coupled to two interrogating antennas, we show that a coherent incident excitation can trigger a self-induced perfect absorption once its intensity exceeds a critical value. Note, that a (near) perfect absorption persists for a broad-band frequency range around the nonlinear coherent perfect absorption condition. Its origin is traced to a quartic behavior that the absorbance spectrum acquires in the proximity of the exceptional points of the nonlinear scattering operator. Coherent perfect absorption allows control of light, with wide ranging applications. Here, this concept is experimentally implemented in the presence of non-linearities, where the formation of a self-induced exceptional point coherent perfect absorption mechanism is identified.

Automated summary

Non-linear coherent perfect absorption mechanism is formed near exceptional point degeneracies of the zeros of the scattering function, allowing for self-induced perfect absorption triggered by a coherent incident excitation exceeding a critical intensity. This broad-band absorption persists around the nonlinear coherent perfect absorption condition due to a quartic behavior acquired in the absorbance spectrum. Coherent perfect absorption provides control of light with wide ranging applications.