Tuning exceptional points with Kerr nonlinearity
Shahab Ramezanpour, Andrey Bogdanov
Abstract
An exceptional point (EP) is a singularity in non-Hermitian systems which exhibits exotic functionalities such as high sensitivity to external perturbations and fine selectivity of a laser mode arising due to the abrupt transition in the eigenvalue spectra. To achieve an EP, both the real and imaginary parts of two or several eigenfrequencies should coincide. Perturbations that appeared at the fabrication stage usually lift the degeneracy, and it impedes the experimental observation of EPs. In this work, we reveal that a Kerr-type nonlinearity can compensate for an initial distortion in resonant frequencies that is hardly avoidable in practice using the example of a pair of coupled ring resonators. We analyze the behavior of the eigenvalues and mode amplitudes in the vicinity of the second- and third-order EPs as a function of excitation amplitude. This work can help to improve the characteristics of the systems that support EPs, broadening their application to the domain of nonlinear photonics.