Influence of Microwave Detuning on Ramsey Fringes of a Single Nitrogen Vacancy Center Spin in Diamond

We investigate the Ramsey fringes of a single electron spin of the nitrogen-vacancy center in diamond with different microwave radiation frequency detunings. The fast Fourier transform demonstrates that the Ramsey fringes consist of three components caused by hyperfine interaction with ¹⁴N nuclear spin, and the Ramsey fringes cannot be well explained without the phase term of the three components, which has not been mentioned before. Each phase is determined by the microwave frequency detuning and the resonant Rabi frequency as well as the π/2 pulse.