Frequency-Tunable and Circularly Polarized Microwave Resonator for Magnetic Sensing With NV Ensembles in Diamond

A microwave (MW) resonator to provide frequency-tunable and circularly polarized MW fields is proposed. This technology enlarges the range of application in optically detected magnetic resonance (ODMR) systems based on the diamond negatively charged nitrogen-vacancy (NV) center and enable the selective excitation of its electronic spins. The characteristics of this resonator are simulated and discussed via a series of experimental studies. An adjustable MW frequency (f
_MW
) can be provided in the 2.5-3.1GHz range and the value of the input return loss (S11) corresponding to f
_MW
measures <; -15 dB which mean at least 96.84% coupling efficiency between the microwave resonator and the microwave source. When f
_MW
is equal to the resonance frequency of the NV center (f
_NV
) for different external magnetic fields (B), the results of the ODMR experiment indicate that the fluorescence increases upon an increase in |B|. Finally, the resonator provides a circularly polarized MW output with a purity of 97.17%. This study paves the way to novel applications and to the development of magnetic sensing devices based on the NV ensemble in diamond.