Fig. 1. (a) NV center energy level diagram, with zero-field splitting D between ground-state electronic spin levels |0〉 and |±1〉. In the presence of a magnetic field, energy levels |±1〉 experience a Zeeman shift, which forms the basis of NV magnetometry. The NV thermometer is based on the |0〉 energy level shifting with temperature. (b) ODMR spectrum of the diamond sensor under a DC bias magnetic field of 46 Gauss, provided by a permanent magnet beneath the head. f₀ is far off resonant frequency. f₁ to f₄ are the maximum slopes of the ODMR spectral line, respectively. (c) Configuration of a time-division multiplexing diamond sensor. A CPC on the bottom of the NV diamond sample, combined with an optical filter and convex lens, guides fluorescence from NV centers to the photodiode. The additional 532 laser is used for reference signals. The pulse generator modulates SW1 and SW2 by means of TTL signals. The output signal of SW1 and SW2 only contains temperature and magnetic field information, and it is sent to LIA1 and LIA2 for processing. (d) Diagram of a time-domain multiplexed frequency modulation time sequence. S₁₁−S₁₂ shows that the signal seen by LIA1 has temperature information. S₂₁−S₂₂ shows that the signal measured by LIA2 gives information about the magnetic field.

Fig. 2. Contour plot of the ratio of ODMR peak and width as a function of light power and MW power.

Fig. 3. Confirmation of simultaneous temperature and magnetic field measurements. (a) Demodulated amplitude value of R of the LIA. The measurement was performed in an environment where a bias magnetic field was applied, the jitter in 0.5 s was caused by activating the electromagnet, and the temperature change was caused by the laser heating after starting the measurement. (b), (c) Dual-frequency driving and frequency modulation are used to measure magnetic fields and temperatures. f₁−f₃ (f₁ − f₄) indicates that the MWs are applied separately in time. f₁ + f₃ (f₁ + f₃) indicates that MWs are applied simultaneously in time. (d) Temperature and magnetic field measurements taken simultaneously; S₁₁ − S₁₂ are the results of LIA1 measurements, which only give temperature. S₂₁ − S₂₂ are the results of LIA2 measurements, which only give magnetic field.

Fig. 4. (a), (b) X and Y are measured under the condition of time-divided measurements. B-X and B-Y are modulated by LIA1. T-X and T-Y are demodulations by LIA2. A magnetic field of 0.2 mT is applied at 0.5 s. (c) Sensitivity is measured as noise power and frequency spectrum.