Nonlinearity-induced scattering zero degeneracies for spectral management of coherent perfect absorption in complex systems

We develop a coherent perfect absorption (CPA) protocol for cases where scale invariance is violated due to the presence of nonlinear mechanisms. We demonstrate, using a microwave setting that lacks geometrical symmetries, that the nonlinearity offers new reconfigurable modalities: the destruction or formation of nonlinear CPAs (NL CPAs), and their frequency positioning and bandwidth management using the incident power as a control knob. The latter occurs via the formation of exceptional point degeneracies of the zeros of nonlinear scattering processes. Our results establish NL-CPA protocols as a versatile scheme for the creation of reconfigurable hot or cold spots in complicated enclosures (e.g., buildings or vessels) with applications to next-generation telecommunications, long-range wireless power transfer, and electromagnetic warfare.