Optical Lattices with Higher-order Exceptional Points by Non-Hermitian Coupling

TL;DR

This paper explores the formation and interaction of multiple higher-order exceptional points in a four-waveguide optical system with non-Hermitian coupling, revealing complex EP patterns and state mixing.

Contribution

It introduces a novel four-waveguide system demonstrating higher-order EPs and their interactions, expanding understanding of EP physics in higher dimensions.

Findings

Unique EP formation patterns in phase diagrams

Calculation of absolute phase rigidities showing state mixing

Potential applications in advanced PT devices

Abstract

Exceptional points (EPs) are degeneracies in open wave systems with coalescence of at least two energy levels and their corresponding eigenstates. In higher dimensions, more complex EP physics not found in two-state systems is observed. We consider the emergence and interaction of multiple EPs in a four coupled optical waveguides system by non-Hermitian coupling showing a unique EP formation pattern in a phase diagram. In addition, absolute phase rigidities are computed to show the mixing of the different states in definite parameter regimes. Our results could be potentially important for developing further understanding of EP physics in higher dimensions via generalized paradigm of nonHermitian coupling for a new generation of parity-time (PT) devices.