Half-space invisible states in dielectric particles.

The concept of invisible optical states in dielectric particles is developed. Two cases for excitation of invisible states are discussed. The first one is the excitation in the microparticles with fixed shapes (e.g. spheres) by variation of the properties of incident radiation. The second one is the search for a complex shape of a particle in which invisible states are excited for fixed properties of the incident radiation (e.g. a plane wave). Based on the proposed numerical assessment of the invisibility of the scattered field, a method for finding invisible particles by varying its shape has been developed. A method for calculating the scattered field is generalized in the framework of the theory of surface perturbation for the case of an arbitrary initial shape of the particle.

Spontaneous Light Emission Assisted by Mie Resonances in Diamond Nanoparticles.

Spontaneous light emission is known to be affected by the local density of states and enhanced when coupled to a resonant cavity. Here, we report on an experimental study of silicon-vacancy (SiV) color center fluorescence and spontaneous Raman scattering from subwavelength diamond particles supporting low-order Mie resonances in the visible range. For the first time to our knowledge, we have measured the size dependences of the SiV fluorescence emission rate and the Raman scattering intensity from individual diamond particles in the range from 200 to 450 nm. The obtained dependences reveal a sequence of peaks, which we explicitly associate with specific multipole resonances. The results are in agreement with our theoretical analysis and highlight the potential of intrinsic optical resonances for developing nanodiamond-based lasers and single-photon sources.