Enhanced Sensitivity with Nonlinearity-Induced Exceptional Points Degeneracy Lifting

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. Bifurcation of exceptional points (EPs) could offer applications in metrology by amplifying sensitivity. The authors find that introducing experimentally nonlinearity can bifurcate the EP degeneracy lifting yielding an elevenfold sensitivity enhancement and a chaotic dynamics near the EP compared to the conventional EP-based approach in the linear regime.