Dynamically crossing diabolic points while encircling exceptional curves: A programmable symmetric-asymmetric multimode switch

TL;DR

This paper introduces a method to control mode switching in multimode non-Hermitian photonic systems by dynamically encircling exceptional curves and crossing diabolic points, enabling advanced light manipulation.

Contribution

It demonstrates a novel approach to multimode switching by winding around exceptional curves and crossing diabolic points in a four-mode PT-symmetric system, overcoming adiabaticity issues.

Findings

Successful control of mode switching in a four-mode PT-symmetric system.

Overcoming adiabaticity breakdown by crossing diabolic points.

Potential for advanced light manipulation in non-Hermitian photonics.

Abstract

Nontrivial spectral properties of non-Hermitian systems can lead to intriguing effects with no counterparts in Hermitian systems. For instance, in a two-mode photonic system, by dynamically winding around an exceptional point (EP) a controlled asymmetric-symmetric mode switching can be realized. That is, the system can either end up in one of its eigenstates, regardless of the initial eigenmode, or it can switch between the two states on demand, by simply controlling the winding direction. However, for multimode systems with higher-order EPs or multiple low-order EPs, the situation can be more involved, and the ability to control asymmetric-symmetric mode switching can be impeded, due to the breakdown of adiabaticity. Here we demonstrate that this difficulty can be overcome by winding around exceptional curves by additionally crossing diabolic points. We consider a four-mode $\cal PT$-symmetric bosonic system as a platform for experimental realization of such a multimode switch. Our work provides alternative routes for light manipulations in non-Hermitian photonic setups.