Effect of spatial-time dispersion on the propagation of electromagnetic waves in photonic crystals

TL;DR

This paper investigates how spatial and temporal dispersion affect electromagnetic wave propagation in three-dimensional photonic crystals, revealing new types of excitations and complex band structures influenced by dispersion effects.

Contribution

It introduces the analysis of dispersion effects on wave vectors and band gaps in photonic crystals, highlighting the emergence of unique polaritons and deformation of the Brillouin zone.

Findings

Dispersion increases the number of transparency bands.

Band gap widths depend on frequency and media parameters.

Wave interactions deform the Brillouin zone, affecting classical Bragg conditions.

Abstract

We study the influence of the space and time dispersion on the frequency dependence of the wave vectors of electromagnetic waves propagating in three-dimensional photonic crystals. Two types of structures are considered: media with weak periodic modulation of the permittivity, and photonic crystals composed of the periodically arranged identical resonant dielectric particles. It is shown that in these systems, in contrast to electrons in solid crystals, different types of excitations exist. For example, a peculiar kind of polaritons arises in the photonic crystals due to the interaction of the electromagnetic field, eigenoscillations of the dielectric medium, and Debye resonance. The widths of the transparency zones and of the band gaps have been calculated as functions of the frequency and of the parameters of the media. It is shown that in the photonic crystals with dispersion, the number of transparency bands is larger than in non-dispersive systems, and the width of the gaps in the frequency spectrum of photons depends on the wave vector. The interaction of different types of waves deforms the Brillouin zone, so that it may not have a plane boundary (for example, a sphere), in which case the classical Bragg condition does not hold.