Dynamically encircling an exceptional point in anti-PT-symmetric systems: asymmetric mode switching for symmetry-broken states

TL;DR

This paper demonstrates that dynamically encircling an exceptional point in anti-PT-symmetric systems induces chiral, asymmetric mode switching in symmetry-broken states, with potential applications in on-chip optical signal processing.

Contribution

It reveals that anti-PT-symmetric systems exhibit chiral dynamics during exceptional point encircling in the PT-broken phase, supported by an analytic theory and experimental validation.

Findings

Chiral dynamics occur in anti-PT systems when encircling an EP in the PT-broken phase.

Experimental demonstration of asymmetric mode switching in three-waveguide systems.

Potential for novel on-chip optical functionalities based on anti-PT symmetry.

Abstract

Dynamically encircling an exceptional point (EP) in parity-time (PT) symmetric systems shows an interesting chiral dynamics, leading to asymmetric mode switching in which the output modes are different when the encircling direction is reversed. Here we show that the dynamical encircling of an EP in anti-PT-symmetric systems can also result in chiral dynamics if the starting/end point lies in the PT-broken phase, in contrast to PT-symmetric systems where chiral dynamics emerges if the starting/end point lies in the PT-unbroken phase. For many applications, such as signal processing using waveguides, the asymmetric mode switching of symmetry-broken modes in anti-PT-symmetric systems is more useful since each eigenmode is localized in one waveguide only. We develop an analytic theory for anti-PT-symmetric chiral dynamics and perform experiments using three waveguides to demonstrate the asymmetric mode switching. The new wave-manipulation phenomena observable in anti-PT-symmetric systems may pave the way towards designing on-chip optical systems with novel functionalities.