Efficient, uniform, and large-volume microwave magnetic coupling to NV centers in diamond using dielectric resonator antennas

Ensembles of nitrogen-vacancy color centers in diamond hold promise for ultra-precise magnetometery, competing with superconducting quantum interference device detectors. Sensor and metrology applications for situations involving high sensitivity require efficient manipulation of the nitrogen-vacancy color centers electronic spins within large volume. Thus, the design of microwave antennas providing a uniform and strong microwave magnetic field over a relatively large volume is on a high demand. In this paper we report different antenna designs based on low loss high permittivity dielectric materials for coherent manipulation of a large ensemble of nitrogen-vacancy color centers in diamond. The operational principle of the proposed antennas is based on excitation of transverse electric (TE) or hybrid electromagnetic (HEM) modes of dielectric resonators. The first antenna design is based on TE01 mode excited inside the resonator made on a ceramic with permittivity of 80. The uniformity of the microwave magnetic field generated by the antenna was verified by measurement of the optically detected magnetic resonance and Rabi frequency in a high-density ensemble of nitrogen-vacancy color centers placed in the center bore of the antenna. Rabi frequency of 10 MHz in a volume of 7 cubic millimeters with a standard deviation of less than 1% at 5 W pump power has been measured at the room temperature. This is enough to coherently excite all color centers in commercially available diamond plates at room temperature. The second antenna design is based on HEM11δ mode excited in the ceramic resonator characterized by the permittivity of 235. The numerical simulations predict the Rabi frequency value of 34.85 MHz in a volume of 6 cubic millimeters with a standard deviation of less than 5% at 5 W pump power. The obtained result paves the way to improve the sensitivity of cutting-edge nitrogen-vacancy color centers based magnetometers by several orders of magnitude, practically reaching superconducting quantum interference device detectors level of sensitivity.