Fig. 1. Characterization of anti-Stokes and Stokes emissions from two types of color centers in 4H-SiC. (a) Excitation and emission schematic: a 980 nm laser is employed to excite silicon vacancies and divacancies simultaneously. The energy level diagram depicts phonon absorption and emission processes during anti-Stokes and Stokes emissions. Energy levels of the excitation process for divacancy centers under Stokes excitation (i) and VSi defects under anti-Stokes excitation (ii). The yellow arrows indicate optical excitation. For normal Stokes excitation, the energy of the emission photon is less than that of the excitation laser, with the phonon sideband emission typically dominating at room temperature. In contrast, for anti-Stokes excitation of silicon-vacancy centers, the photon energy of the laser energy is less than the transition, necessitating phonon absorption, as indicated by the blue square in the energy level diagram. (b) Optical setup schematic: the fluorescence from Si vacancies and divacancies is bifurcated into two channels by a beam splitter and subsequently collected post-filtering by an SNSPD and an APD. Key components are labeled as BS (beam splitter), LP (long-pass filter), and SP (short-pass filter). (c) Photoluminescence spectrum: the emission peaks associated with silicon vacancies (black) and divacancies excited by a 980 nm laser are illustrated. (d) Microwave system diagram: microwaves traverse through a dual-switch setup enabling 20 Hz modulation for continuous waveforms and pulse modulation for rapid spin control. The output feeds into a lock-in amplifier (Stanford Research System SR830) for detection enhancement. (e) ODMR spectrum for silicon-vacancy centers under anti-Stokes excitation. (f) ODMR spectrum for PL5 and PL6 across a magnetic field (0–30 Gauss): the depicted spectra highlight the behavior of PL5 and PL6 emissions under an increasing c-axis magnetic field, demonstrating divergent and bending trends, respectively.

Fig. 2. Characterization of anti-Stokes and Stokes emission. (a) Schematic illustration and a photo of the temperature change device. The sample is attached to a ceramic piece and heated by applying voltage to the TEC module. (b) Temperature dependence of anti-Stokes fluorescence from silicon vacancy. Each data point was collected over a 20 min period with measurements taken at 50 ms intervals, and the error bars represent the standard deviation of these measurements. The data fits well with the Arrhenius-type equation Ae−EakBT, and Ea=89.7  meV is coincident with ZPL of silicon-vacancy at 917 nm (86.9 meV). (c) Change of Stokes fluorescence with temperature. (d) Temperature dependence of anti-Stokes to Stokes PL ratio. The ratio fits an exponential curve a+becT−T0, showing high sensitivity in temperature sensing applications.

Fig. 3. Attributes of nanoscale thermometry. (a) Longtime trace of anti-Stokes to Stokes PL ratio over 20 min, displaying the stability of measurement. (b) Uncertainty as a function of integration time. The temperature resolution is ηT=δTtm, where tm is the integration time.

Fig. 4. Confocal scan of Anti-stokes emission at different temperatures from around 306 K to 412 K.