Fig. 4: Homogeneous linewidth and state preparation.
From: Check-probe spectroscopy of lifetime-limited emitters in bulk-grown silicon carbide
a Experimental sequence. A resonant laser at f1 and a microwave (MW) pulse resonant with the ground-state spin transition act as a resonance check, initialising the optical transition near f1. Next, a second laser probes the defect emission at f2 (for 2 ms), yielding a measurement of the linewidth with minimal disturbance. b Experimental data showing narrow optical transitions, with the bottom (top) data corresponding to a waiting time of 5 μs (40 ms) between the f1 and f2 laser pulses (offset for clarity). Data are fitted to a Lorentzian with a FWHM of 39(3) MHz (44(6) MHz). The counts threshold is set to T = 7 during the f1 pulse. c Data and fits as in (b)(bottom), scanning f2 around f1, when f1 is set at different frequencies (various shades of red) within the broad diffusion-averaged line measured in Fig. 1g. d Measured resonance center frequency as a function of the set f1 frequency (solid grey line: f = f1). The defect emission frequency can effectively be tuned over a GHz range. e Corresponding linewidths extracted from (c), with inverse-variance weighted mean 36(1) MHz (solid grey line). The shaded region denotes the expected minimum linewidth (~36 MHz), given the lifetime limit of ~20 MHz, and correcting for power broadening (~26 MHz, Fig. 5j) and residual inhomogeneous broadening (~15 MHz, Eq. (2)).
