High-Q resonances with low azimuthal indices in all-dielectric high-index nanoparticles

Recently, a novel class of high-Q optical resonators based on all-dielectric subwavelength nanoparticles with high refractive index has been proposed [M. V. Rybin, et al, arXiv:1706.02099, 2017]. Here we study a complex spectrum of such nanoscale resonators by means of the resonant-state expansion, treating the problem as a nonHermitian eigenproblem. We show that the high-Q features can be described within the mechanism of external coupling of open channels via the continuum. For ceramic resonators with permittivity = 40, we demonstrate that the quality factor of a trapped mode with a low azimuthal index could reach the value Q = 104.This work has been supported by the Ministry of Education and Science of the Russian Federation (3.1668.2017/4.6) and the Russian Foundation for Basic Research (16-02-00461, 16-37-60064, 17-02-01234)