Fig. 2: In situ temperature measurement for laser-heated DAC.

a A schematic illustration of the ultrafast thermometry setup. Instead of measuring the entire thermal radiation spectra, the integrated intensity ratio of two radiation windows, A: 900–1450 nm and B: 1550–2200 nm, was used for the temperature measurement. b Temperature (red curve) has been calibrated based on the ratio (windows: B/A) of the intensities recorded by two detectors (gray and black curves). The temperature curve was measured with 1-µs temporal resolution. Temperature oscillations displayed between 2 and 7 ms might be due to a phase transition of the tungsten metal. c A pressure-temperature synthesis diagram of SiV-containing diamond is shown with red circles and blue crosses representing the formation of SiV and no formation of SiV, respectively. Dashed lines indicate the phase boundary for the formation of SiV, as evidenced by the PL peak of SiV’s ZPL. d At 18.4 GPa, with a laser intensity of 33 MW/cm² and a beam spot of 2.5 μm (FWHM), a 5-μs induction time was observed for the formation of the SiV center, which equals an energy fluence of 0.165 kJ/cm². After heating for 500 μs, the error bar of the temperature measurements becomes large due to temperature oscillations. The temperature error bars are from the fitting of the data.