Coupling between Fano and Bragg bands in photonic band structure of two-dimensional metallic photonic structures

TL;DR

This paper investigates the interaction between Fano and Bragg bands in the photonic band structure of two-dimensional metallic photonic structures, revealing how their coupling influences transmission spectra and field distributions.

Contribution

It identifies and analyzes the coupling between Fano and Bragg bands in 2D metallic photonic crystals, providing insights into their formation and symmetry properties.

Findings

Fano bands manifest as Fano resonances in transmittance.

The interplay between scattering mechanisms affects band structure properties.

Spatial magnetic field distributions reflect band symmetry characteristics.

Abstract

Frequency and transmission spectrum of two-dimensional array of metallic rods is investigated numerically. Based on the recent analysis of the band structure of two-dimensional photonic crystal with dielectric rods [P. Marko\v{s}, Phys. Rev. A 92 043814 (2015)] we identify two types of bands in the frequency spectrum: Bragg (P) bands resulting from a periodicity and Fano (F) bands which arise from Fano resonances associated with each of the cylinders within the periodic structure. It is shown that the existence of Fano band in a certain frequency range is manifested by a Fano resonance in the transmittance. In particular, we re-examine the symmetry properties of the H- polarized band structure in the frequency range where the spectrum consists of the localized modes associated with the single scatterer resonances and we explore process of formation of Fano bands by identifying individual terms in the expansion of the LCAO states. We demonstrate how the interplay between the two scattering mechanisms affects properties of the resulting band structure when the radius of cylinders is increased. We show that a different character of both kinds of bands is reflected in the spatial distribution of the magnetic field which displays patterns corresponding to the corresponding irreducible symmetry representations.