Exceptional points and asymmetric mode conversion in quasi-guided dual-mode optical waveguides.

Y D Chong,S N Ghosh

doi:10.1038/srep19837

Abstract

Non-Hermitian systems host unconventional physical effects that be used to design new optical devices. We study a non-Hermitian system consisting of 1D planar optical waveguides with suitable amount of simultaneous gain and loss. The parameter space contains an exceptional point, which can be accessed by varying the transverse gain and loss profile. When light propagates through the waveguide structure, the output mode is independent of the choice of input mode. This “asymmetric mode conversion” phenomenon can be explained by the swapping of mode identities in the vicinity of the exceptional point, together with the failure of adiabatic evolution in non-Hermitian systems.

Highlights

Non-Hermitian systems host unconventional physical effects that be used to design new optical devices
Many ideas from quantum mechanics have inspired the design of photonic structures, such as photonic crystals; recently, photonics researchers have drawn ideas from non-Hermitian quantum mechanics[1,2]
Waveguide structures with balanced of loss and gain regions have been used to achieve parity-time (PT ) symmetry[1,14,15,16,17]; the PT -breaking transition is a known example of an exceptional point (EP), but PT symmetry is not the only way to realize EPs, and in this paper we will not be constrained to PT symmetry

Summary

Introduction

Non-Hermitian systems host unconventional physical effects that be used to design new optical devices. One interesting phenomenon occurring in non-Hermitian systems is the exceptional point (EP): a point in parameter space where the Hamiltonian becomes defective, and two eigenstates coalesce[3,4]. An encircling of the EP can be realized via a spatial variation in the gain/loss profile.

Results

Conclusion