Multipole analysis of bound states in the continuum supported by a periodic array of spheres

Abstract

In this work we propose an alternative explanation of the both symmetry-protected and accidental BIC's origin in terms of multipole moments and a group-theoretical approach. We develop an analytical method determining the contribution of vector spherical harmonics to the far field, which helps to find symmetry allowed and forbidden spherical harmonics describing bound states in the continuum. We explore a multipole expansion of eigenmodes and explain formation mechanism of bound states in the continuum in periodic dielectric nanospheres. Show more