Light propagation and magnon-photon coupling in optically dispersive magnetic media

TL;DR

This paper develops a theoretical framework for magnon-photon coupling in dispersive, epsilon-near-zero media, highlighting enhanced coupling near the ENZ frequency and polarization effects, aiding the design of optomagnonic systems.

Contribution

It provides a detailed derivation of the magnon-photon coupling Hamiltonian in dispersive media and explores the effects of dispersion and polarization on coupling strength.

Findings

Enhanced magnon-photon coupling near ENZ frequency

Polarization selection rules cause coupling vanishing at specific frequencies

Lorentz dispersion model illustrates theoretical predictions

Abstract

Achieving strong coupling between light and matter excitations in hybrid systems is a benchmark for the implementation of quantum technologies. We recently proposed [arXiv:2110.02984] that strong single-particle coupling between magnons and light can be realized in a magnetized epsilon-near-zero (ENZ) medium, in which magneto-optical effects are enhanced. Here we present a detailed derivation of the magnon-photon coupling Hamiltonian in dispersive media both for degenerate and non-degenerate optical modes, and show the enhancement of the coupling near the ENZ frequency. Moreover, we show that the coupling of magnons to plane-wave non-degenerate Voigt modes vanishes at specific frequencies due to polarization selection rules tuned by dispersion. Finally, we present specific results using a Lorentz dispersion model. Our results pave the way for the design of dispersive optomagnonic systems, providing a general theoretical framework for describing engineering ENZ-based optomagnonic systems.