Dual-Wavelength Analysis of Nitrogen-Vacancy Center Quantum Magnetometry Enhanced by Uniformly Coated Gold Nanoparticles

We present a dual-wavelength analysis of nitrogen-vacancy (NV) center quantum magnetometry enhanced by uniformly coated gold nanoparticles (AuNPs). An ensemble-averaged model is developed to analyze the AuNP-enhanced stimulated absorption at the 532 nm excitation wavelength and the spontaneous emission at 637 nm. The resulting detected optically magnetic resonance (ODMR) signal profiles are simulated for both enhancement mechanisms. We find that the enhanced stimulated absorption at 532 nm significantly amplifies the ODMR signal intensity without broadening the linewidth, thereby improving the signal-to-noise ratio (SNR) without sacrificing the magnetic field sensing resolution. Conversely, enhancing the 637 nm spontaneous emission increases the total photo emission rate but simultaneously broadens the ODMR detection linewidth due to the direct reduction in the effective spin coherence time of excited states by the enhanced spontaneous rate. The dual-wavelength analysis provides valuable design guidance for the development of low-cost spin-coated AuNP-enhanced NV-center quantum magnetometry technologies.