Universal Characterisation of Cavity--Magnon Polariton Coupling Strength Verified in Modifiable Microwave Cavity

TL;DR

This paper presents a universal method to characterize cavity-magnon coupling strength using a re-entrant cavity, validated by experiments, allowing precise engineering of coupling in various cavity designs without geometric limitations.

Contribution

It introduces a re-entrant cavity-based approach and reworked theory for predicting coupling strength solely from simulations, enabling advanced cavity-magnon experiments.

Findings

Achieved strong coupling between 20-140 MHz.

Validated the reworked theory experimentally.

Demonstrated feasibility of deep strong coupling regime.

Abstract

A comprehensive study of the frequency dependence of the photon-magnon coupling for different magnetic samples is made possible with a tuneable 3D--printed re--entrant cavity. Strong coupling is achieved, with values ranging between 20--140 MHz. The reworked theory, experimentally verified for the first time here, enables coupling values to be calculated from simulations alone, enabling future experiments with exotic cavity designs to be precisely engineered, with no limitations on sample and cavity geometry. Finally, the requirements of the deep strong coupling regime are shown to be achievable in such experiments.