Fast passage effect in cw-ODMR of an ensemble of NV− centers

A rapid scan technique of the magnetic field has been developed to improve excitation efficiency in continuous wave (cw)-electron spin resonance. The resulting passage effects induce significant responses of magnetizations, most notably an inversion of longitudinal magnetization. The change in longitudinal magnetization can be observed in optically detected magnetic resonance (ODMR), but the passage effect has not been investigated in cw-ODMR spectroscopy. In this study, we combine the ODMR technique with the rapid scan of the magnetic field to demonstrate the impact of fast passage effects on the field-swept cw-ODMR. An ensemble of negatively charged nitrogen-vacancy (NV−) centers in a diamond crystal is used as a model system. By selecting the fast passage adiabatic region among six distinct passage regions, efficient ODMR detection is achieved through the macroscopic control of longitudinal magnetization. Experimental results are explained by the numerical analyses of classical time-dependent Bloch equations and related rate equations under an optical cycle. This knowledge paves the way for the facilitation of versatile applications of ODMR for quantum sensors.