Abstract
The dynamical encirclement around a second-order exceptional point (EP) and corresponding chirality driven nonadiabatic modal dynamics have attracted enormous attention in the topological study of various non-Hermitian systems. However, dynamical encirclement around multiple second-order EPs in a multistate system is yet to be explored. Here, exploiting an exclusive design of a planar gain-loss assisted three-mode supported optical waveguide with local Kerr nonlinearity, we encounter multiple second-order EPs. Judiciously, choosing a specific parameter space by varying the unbalanced gain-loss profile, we encircle multiple EPs simultaneously, and explore the beam dynamics toward corresponding chiral or nonchiral aspects of the device. While propagating through the designed waveguide, three coupled modes are collapsed into a specific dominating mode, owing to corresponding nonadiabatic corrections around multiple EPs. We reveal that in the absence of chirality the same amount of focusing- and defocusing-type nonlinearity gives different dominating output, irrespective of the choice of inputs, for the same topological structure of the waveguide. An analytical model to describe this anomalous mode collapsing phenomenon due to interplay between nonlinearity and the EP has been developed. Our findings should provide a promising opportunity to switch or retrieve a selective mode from a multimode signal in integrated devices.