# Axion Detection with Cavity Arrays

## TL;DR

This paper explores cavity arrays with negative and positive couplings to enhance axion detection sensitivity by increasing mode volume without changing frequency, using eigenmode analysis and 3D FEM modeling.

## Contribution

It introduces a novel cavity array design with controllable dispersion properties, demonstrating potential for improved axion search sensitivity through larger mode volumes.

## Key findings

- Negative mutual coupling creates higher frequency modes with larger mode volumes.
- Chiral structures enable control of dispersion properties in cavity arrays.
- Arrays of metallic rods can realize these effects in practical setups.

## Abstract

Using eigenmode analysis and full 3D FEM modelling, we demonstrate that a closed cavity built of an array of elementary harmonic oscillators with negative mutual couplings exhibits a dispersion curve with lower order modes corresponding to higher frequencies. Such cavity arrays may help to achieve large mode volumes for boosting sensitivity of the axion searches, where the mode volume for the composed array scales proportional to the number of elements, but the frequency remains constant. The negatively coupled cavity array is demonstrated with magnetically coupling coils, where the sign of next-neighbour coupling (controlled with their chirality) sets the dispersion curve properties of the resonator array medium. Furthermore, we show that similar effects can be achieved using only positively coupled cavities of different frequencies assembled in periodic cells. This principle is demonstrated for the multi-post re-entrant system, which can be realised with an array of straight metallic rods organised in chiral structures.