ИСТИНА

Diamond particles with color centers have found numerous applications in quantum optics, bioimaging and nanosensing. Here, we report on an experimental study of the optical Mie resonances of subwavelength diamond particles and their effect on the fluorescence of nitrogen- vacancy centers. We employ single-particle scattering spectroscopy to reveal the fundamental optical resonances of individual diamond particles and measure the fluorescence saturation curves using continuous-wave excitation to evidence the difference in the spontaneous emission rate of the color centers in different particles. A simple analytical model has been used to predict the dependence of the saturation intensity on the particle size for a free-standing spherical diamond. Experimentally, we have shown that the magnetic dipole and quadrupole modes are excited in the fluorescence spectral range for particles of approximately 250–350 nm in size and that the saturation intensity for such particles is by an order of magnitude higher than for a smaller one, which is in agreement with our calculations. The results demonstrate that the efficiency of diamond-based sensors and single-photon sources can be improved by simply choosing particles of a proper size.