Microwave power self-coherent reference measurement based on ensembles of nitrogen-vacancy centers in diamond

Microwave detection based on optical detection magnetic resonance technology (ODMR) of nitrogen-vacancy (NV) centers is simple and non-invasive. However, in high microwave power ranges, saturation appears and cannot be used for accurate power measurement. The self-coherent reference measurement for high-power microwave based on ODMR of NV centers has been demonstrated. Firstly, by introducing the principle of microwave self-coherent reference, that is, by adjusting the phase difference to achieve power regulation of microwave, a conversion model by phase modulation between enhancement and attenuation of microwave power is introduced. Then, the microwave self-coherent reference measurement is established under combinations of microwave power with different phase settings. Combined with the frequency modulation technology, the sensitivity of measurement is significantly improved from 4.59 nT/Hz^1/2 to 67.69 pT/Hz^1/2. The maximum measurement range of microwave power can be extended to 2×10⁴ times the initial saturated power of direct measurement with ODMR. The results show that the method efficiently overcomes saturation under the direct measurement of ODMR and provides useful technical assistance for near-field detection, performance monitoring, and problem diagnostics for microwave devices.