We present a multipolar model of surface-lattice resonances (SLRs) in two-dimensional arrays of spheres including the electric dipole, magnetic dipole, and electric quadrupole moments of the spheres. We identify SLRs of dipolar and multipolar character, show the importance of nonresonant multipoles in their description, and discuss the sensitivity of SLRs to illumination conditions. We link SLRs to an excitation of modes supported by the array, and we propose a simplified model of the mode dispersion relations that explains the sensitivity of SLRs and the band gap in mode dispersion found at low frequencies. Finally, we discuss the resonant features associated with a direct coupling to a mode which can occur in addition to the diffractive coupling signaled by SLRs.

• Received 3 March 2017
• Revised 18 April 2017

DOI:https://doi.org/10.1103/PhysRevB.95.195406