Exceptional points in perturbed dielectric spheres: A resonant-state expansion study

Netherwood, K. S., Riley, H. and Muljarov, E. A. ORCID: https://orcid.org/0000-0002-2878-4148 2024. Exceptional points in perturbed dielectric spheres: A resonant-state expansion study. Physical Review A 110 (3) , 033518. 10.1103/PhysRevA.110.033518

Preview

PDF - Published Version Available under License Creative Commons Attribution. Download (23MB) | Preview

Abstract

Exceptional points (EPs) in open optical systems are rigorously studied using the resonant-state expansion (RSE). A spherical resonator, specifically a homogeneous dielectric sphere in a vacuum, perturbed by two pointlike defects which break the spherical symmetry and bring the optical modes to EPs, is used as a worked example. The RSE is a nonperturbative approach encoding the information about an open optical system in matrix form in a rigorous way, and thus offering a suitable tool for studying its EPs. These are simultaneous degeneracies of the eigenvalues and corresponding eigenfunctions of the system, which are rigorously described by the RSE and illustrated for perturbed whispering-gallery modes (WGMs). An exceptional arc, which is a line of adjacent EPs, is obtained analytically for perturbed dipolar WGMs. Perturbation of high-quality WGMs with large angular momentum and their EPs are found by reducing the RSE equation to a two-state problem by means of an orthogonal transformation of a large RSE matrix. WGM pairs have opposite chirality in spherically symmetric systems and equal chirality at EPs. This chirality at EPs can be observed in circular dichroism measurements, as it manifested itself in a squared-Lorentzian part of the optical spectra, which we demonstrate here analytically and numerically in the Purcell enhancement factor for the perturbed dipolar WGMs.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Physics and Astronomy
Publisher:	American Physical Society
ISSN:	2469-9926
Date of First Compliant Deposit:	30 May 2024
Date of Acceptance:	21 May 2024
Last Modified:	08 Nov 2024 02:00
URI:	https://orca.cardiff.ac.uk/id/eprint/169304

Actions (repository staff only)

Edit Item