Methodology of improving sensitivity of silicon vacancy spin-based sensors based on double spiral coil RF resonance structure

Abstract

<sec> Due to the power instability and field non-uniformity of radio frequency (RF), microwave (MW) and laser signals, inhomogeneous broadening of spin magnetic resonance line causes the absorption to decrease in a nuclear resonance system, which can reduce the sensitivity of spin-based sensing and testing technology. In this paper, we propose and design a double solenoid coil RF resonance antenna structure. The nearly uniform RF field density is produced by the two solenoid coil antenna structures that are parallel to the symmetry axis. The size of the uniformity in the center region of double solenoid coil RF resonance antenna structure is about π×375 mm<sup>2</sup> × 10 mm. And the non-uniformity is less than 0.9%. Comparing with a single straight wire antenna and the single solenoid coil RF resonance antenna structure, the uniformity is improved by about 56.889 times and 42.889 times, respectively. At the same time, based on the near-field mutual inductance coupled resonance effect, the intensities of RF field in the center region of the two-solenoid coil antenna structure is enhanced. Comparing with the single solenoid coil antenna structures, it is enhanced by about 1.587 times. And the equivalent sensitivity of the silicon vacancy color center spin based sensor is enhanced by about 4.833 times.</sec><sec> In the experiment, an optical detection magnetic resonance measurement system based on the spin magnetic resonance effect of silicon vacancy color center in single crystal SiC is built. Comparing with the single straight wire antenna and the single solenoid coil RF resonance antenna structure, the contrast of the silicon vacancy color center spin magnetic resonance signals of the double solenoid coil RF resonance antenna structure increases about 6 times and 2.4 times, respectively. The sensitivity of the spin-based sensor is increased by 4.833 times and 2.071 times through using the modulation and demodulation method, and the noise decreases by 8 times and twice. Hence, based on this double solenoid coil RF resonance antenna structure, the sensitivity of the silicon vacancy spin sensor can be improved. Combined with chip manufacturing technology of SiC wafer, it proves to be a potential approach to developing the high precision, chip scale spin sensor devices and measurement technology.</sec>