Development of a cavity with photonic crystal structure for axion searches

TL;DR

This paper reports the development and testing of photonic crystal structured cavities, called DRiPC cavities, with tunable resonance frequencies suitable for axion search experiments, demonstrating good agreement with simulations and promising features for future research.

Contribution

The study introduces DRiPC cavities with a novel photonic crystal structure, showing their tunability, high agreement with simulations, and potential for axion searches.

Findings

Resonance frequency tunability from 5.10 GHz to 6.72 GHz.

Excellent agreement between experimental results and finite element simulations.

TM010-like electric field mode observed across a range of grid intervals.

Abstract

Two cavities in different size with the photonic crystal structure have been developed for axion searches. In the cavities, the dispersion relation in the photonic crystal is utilised, and so was named to "DRiPC cavities". The size of the smaller one is 100 mm x 100 mm x 10 mm, where 16 cylindrical metal poles with a diameter of 4 mm are introduced in a 4x4 grid at 20 mm intervals. In this study, the grid interval in x direction in the small size cavity, Lx, was changed to investigate resonance frequency, Q-value, and electric field profile at each Lx. The lowest three frequencies have been compared with the ones simulated by the finite element method to be found in excellent agreement. The lowest frequency mode could be tuned from 5.10 GHz (Lx = 25.0 mm) to 6.72 GHz (13.9 mm), centering on 5.87 GHz at Lx = 20 mm. This wide range tunability, 27.7%, was suitable for a search with a modest Q-value. By examining the electric field distributions with the bead pull method, the lowest frequency mode at Lx = 16.0 - 25.0 mm were TM010-like. This mode was also obtained in a larger size cavity (180 mm x 180 mm x 20 mm x 2) with the same photonic crystal structure. These results led us to conclude a DRiPC cavity has the noble features for future axion search experiments.