Optimization of power broadening in optically detected magnetic resonance of defect spins in silicon carbide

Defect spins in silicon carbide have become promising platforms with respect to quantum information processing and quantum sensing. Indeed, the optically detected magnetic resonance (ODMR) of defect spins is the cornerstone of the applications. In this work, we systematically investigate the contrast and linewidth of laser and microwave power-dependent ODMR with respect to ensemble-divacancy spins in silicon carbide at room temperature. The results suggest that magnetic field sensing sensitivity can be greatly improved for the optimized laser and microwave power range. The experiment will be useful for the applications of silicon carbide defects in quantum information processing and ODMR-dependent quantum sensing.

Figure 1

Saturation curve and ODMR spectrum of divacancy defects. (a) The saturation behavior of divacancy defects at different laser powers. (b) Comparison of the counts of the superconducting single-photon detector and the voltage of the Femto photoreceiver. (c) The ODMR spectrum of divacancy defects at a magnetic field of zero. (d) The ODMR spectrum of divacancy defects as a function of the magnetic field.

Figure 2

Coherent control of PL6 defects at room temperature. (a) Three Rabi oscillations with different MW powers (the red lines represent data fitting using the exponentially decaying cosine function, and the inset shows the Rabi frequencies). (b) Rabi frequencies increase linearly with the square root of the total MW power on the copper wire (the red line is a linear fit). (c) Ramsey oscillation of the defects (the MW frequency detunes for 4.4 ± 0.2 MHz). (d) Spin-echo measurement of the defect spins (the red line represents data fitting using the decaying exponential function [1]).

Figure 3

ODMR signals of PL6 defects. (a) The ODMR measurement of defects with a wide MW frequency scanning range at a magnetic field of 3.25 mT (the red line represents the data fit using the Lorentzian function). (b) The ODMR measurement of the left branch of the PL6 at low laser power ($1\mathrm{mW}/\mu {\mathrm{m}}^2$) and 0.18 MHz Rabi frequency (the red line is the data fit using three Lorentzian functions, the center peak consists of the PL6 electron spin signals that were not strongly coupled to any nuclear spins, and the two small peaks correspond to the PL6 electron spins signals that were strongly coupled with ${}^{29}\mathrm{Si}$ nuclear spins of 9.8 ± 0.2 MHz). (c) Three representative ODMR measurements at different Rabi frequencies for a laser power of $2\mathrm{mW}/\mu {\mathrm{m}}^2$ (the ODMR signal was magnified five times for 0.18 MHz MW power). (d) Three representative ODMR measurements at different laser powers for a Rabi frequency of 2.1 MHz (a sum of three Lorentzian peaks was used to fit the data at a laser power of 0.3 and $2\mathrm{mW}/\mu {\mathrm{m}}^2$).

Figure 4

Laser- and MW power-dependent ODMR contrast and linewidth. (a) and (b) represent the ODMR contrast and linewidth of three different Rabi frequencies as a function of laser power plotted in log scale, respectively. (c) and (d) represent the ODMR contrast and linewidth of three different laser powers as a function of Rabi frequency plotted in log scale, respectively.

Figure 5

(a) Two-dimensional plot of the experimental magnetic field sensitivity as a function of laser power and Rabi frequency (the lines represent the isomagnetic field sensitivities).