Solid State Spin Ensemble Coupled with a Room-Temperature Planar Resonator

Spin-cavity coupling with solid state quantum defects possessing long room temperature coherence times could improve performance in a number of platforms, including magnetometry, masing, time keeping, and EPR spectroscopy. Due to their typical microwave frequency ground state splittings, free-space cavity modes span decimetre lengths, preventing miniaturization and resulting in poor geometric overlap between the spin ensembles and cavity mode. A new planar inverse anapole (PIA) microwave resonator using gold deposited on sapphire generates a smaller mode volume in a chip-like form factor more readily transitionable to compact devices. We demonstrate coupling an ensemble of hyperpolarized diamond nitrogen-vacancy centers to a PIA resonator and characterize the coupling for a range of input powers. Furthermore, we apply a multiplexed lock-in detection scheme to perform vector magnetometry with a single cavity mode, and compare the performance to other platforms.