| Summary: | 碩士 === 國立臺灣大學 === 物理學研究所 === 107 === In this thesis, we study spin relaxation of ground electronic triplet states in nitrogen-vacancy color center in fluorescent nanodiamond (FND). We measured the relaxation time from the ms = 0 state to equal distribution in the ms = 0, ±1 states, under the influence of a near-resonant microwave field. In data analyses, we first fitted the experimental data to single-exponential decay, from which we determined the relaxation time vs. the frequency and power of the applied microwaves. By plotting the relaxation time vs. microwave frequency, we constructed a relaxation spectrum, with a spectral shape close to that of the spin resonance spectrum. The spin resonance for and transition is ~2.87 GHz, which is commonly determined by optically detected magnetic resonance (ODMR) method, we thus coin our new method the optically detected relaxation spectroscopy (ODRS). In the resonance condition, the brightness of an FND is reduced by 10%, while the spin relaxation time can be much shorter than the intrinsic longitudinal relaxation time, T1, depending on the microwave power. Thus the ODRS gives a spectrum with a much higher contrast than that of an ODMR spectrum.
Finally, we fitted our data to a 3-level atom model, from which we determined T1 ~1290 μs. We further fitted the data to determine the Rabi frequencies which are 0.05 - 0.14 MHz for microwave powers 0.2 – 6 mW. In the future, we may can develop a nano-sensor for determining the frequency and power of a microwave utilizing spin relaxation in FND.
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