High-Q Photonic Bandgap Microwave Cavity for Dark Matter Axion Searches

A 3D photonic bandgap (PBG) crystal forbids the propagation of electromagnetic waves with energy within a certain range in all directions. We create an electromagnetic cavity by designing a defect inside the crystal such that its frequency lies within the forbidden gap. With enough number of periods in the crystal, the Q-factor is only limited by the dielectric loss in the material. One of the potential applications is in the Axion Dark Matter search, which is currently limited by the usage of low Q-factor copper cavities due to the presence of a strong magnetic field. We present various designs and experimental results of dielectric materials which can significantly increase the sensitivity and scanning rate of axion search. We predict the Q-factor of a PBG cavity to increase in the presence of a large magnetic field due to the shift in the two-level system energies to a higher level.