Probing Kerr-induced higher-order exceptional points in atom-coupled microring resonators

This article explores the eigenvalue spectrum and exceptional point (EP) behavior in two coupled optical micro-ring resonators interacting with a four-level atomic medium, emphasizing the impact of Kerr-nonlinearity. At zero Kerr effect, a third-order exceptional point (EP-3) appears at a specific atomic transition frequency, marking a transition from weakly interacting, dissipative modes to strongly hybridized, gain-dominated modes. Introducing Kerr-nonlinearity shifts and sharpens these EPs, induces nonlinear effects such as asymmetric splitting and self-trapping, and modulates gain–loss dynamics. The contour analyses reveal multiple second-order EPs and the emergence of EP-3 under strong Kerr influence. The findings underscore Kerr-nonlinearity as a crucial mechanism for tuning exceptional points, enabling precise control over mode interactions and nonlinear optical responses in hybrid micro-ring resonator atomic systems. Overall, the results provide comprehensive insights into the interplay between non-Hermitian physics, nonlinear optics, and atomic interactions in micro-ring resonator systems. This work advances understanding of nonlinear exceptional point physics in hybrid photonic–atomic platforms, highlighting the potential for enhanced control of light–matter interactions through Kerr nonlinearity modulation.