A tunable photonic band gap resonator for axion dark matter searches

TL;DR

This paper introduces the first tunable photonic band gap resonator designed for axion dark matter searches, offering improved mode selectivity and tunability over traditional microwave resonators used in haloscopes.

Contribution

It presents a novel, tunable PBG resonator that enhances mode control and frequency tuning for axion detection experiments, overcoming limitations of existing cylindrical cavities.

Findings

Successful confinement of the TM$_{010}$ mode across the tuning range

Elimination of TE modes within the operational bandwidth

Demonstrated tunability and mode selectivity of the PBG resonator

Abstract

Axions are a well-motivated dark matter candidate particle. Haloscopes aim to detect axions in the galactic halo by measuring the photon signal resulting from axions interacting with a strong magnetic field. Existing haloscopes are primarily targeting axion masses which produce microwave-range photons and rely on microwave resonators to enhance the signal power. Only a limited subset of resonator modes are useful for this process, and current cylindrical-style cavities suffer from mode mixing and crowding from other fundamental modes. The majority of these modes can be eliminated by using photonic band gap (PBG) resonators. The band gap behavior of these structures allows for a resonator with mode selectivity based on frequency. We present results from the first tunable PBG resonator, a proof-of-concept design with a footprint compatible with axion haloscopes. We have thoroughly characterized the tuning range of two versions of the structure and report the successful confinement of the operating TM$_{010}$ mode and the elimination of all TE modes within the tuning range.