Enhanced sensitivity with nonlinearity-induced exceptional points degeneracy lifting

Abstract

Bifurcation of exceptional points (EPs), particularly higher-order EPs, can offer applications in metrology by amplifying sensitivity, but this method suffers from a tradeoff between sensitivity and robustness. To break this constraint, we experimentally introduce nonlinearity into the EP degeneracy lifting at the coupled electric resonators and observe a sixth-order nonlinear bifurcation which amplifies the sensitivity elevenfold compared to the conventional EP-based approach operating in the linear regime, while maintaining the degrees of freedom, thereby without cost in robustness. Moreover, we discover a chaotic dynamics near the EP due to the nonlinear contribution, which constitutes a distinct difference from the EP degeneracy lifting in the linear regime with random noise. Our study expands the scope of EP degeneracy lifting into nonlinearity, providing a paradigm to exploit the benefit of EPs.