Principal Investigator Dirk Englund
Co-investigator Ruonan Han
Nitrogen-vacancy (NV) centers in diamond have attracted attention for spin-based quantum sensing in ambient conditions. They have demonstrated outstanding nanoscale sensing and imaging capabilities for magnetic-fields. However, these sensing systems require many discrete devices to operate. This limits their scalability. In this work, we demonstrate a chip-scale CMOS and NV integrated platform for magnetic field sensing. The CMOS chip performs the required spin manipulation and read-out functions for NV sensing protocols.
Magnetic field sensing is accomplished by determining the spin states of the NV. The frequency of the spin states is determined by through optically detected magnetic resonance (ODMR). The magnetic field is proportional to the frequency splitting of the spin states (2.8 MHz/Gauss). The system has an on-chip microwave (MW) signal generator, operating from 2.6 GHz to 3 GHz. In addition, an on-chip coil with parasitic loops radiates the AC magnetic field with an amplitude up to 10 Gauss with 95% uniformity over 50 µm x 50 μm. This MW radiation efficiently manipulates the NV spin ensembles. This is followed by on-chip optical readout of the spin state. A CMOS-compatible metal-dielectric structure filters out the optical pump (532 nm) with an isolation of 10 dB. An on-chip patterned P+/N-Well photodiode, beneath the MW coil and the filter, detects the NV red fluorescence. This photodiode is patterned to reduce the unwanted coupling to the MW coil. The measured photodiode responsivity is 230mA/W. The proposed system opens the door for a highly integrated quantum system with applications in the life sciences, tracking, and advanced metrology.