Scattering Spectra and Hot Spots in Dielectric Ring and Ring-disk Dimer

We studied experimentally and theoretically the scattering spectra and electromagnetic field distribution patterns during a topological transition from a dielectric disk to a ring and in a “disk inside a ring” dimer. Using electromagnetic field patterns, we detected hot spots in the ring-disk dimer, as well as in the ring with the small hole, during the disk-ring topological transition. At the moment of formation of the coaxial air hole in the disk, a hot spot flares up, which is formed due to the Mie resonance m = 1, while other Mie resonances do not contribute to the effect due to symmetry. In the dimer, upon point contact between the ring and the disk, resonance hot spots were observed, which dissapear when the disk was displaced towards the center of the ring. The correspondence of the resonance hot spot frequency to the eigenmodes of the dimer is analyzed.