Negative group velocity in layer-by-layer chiral photonic crystals

TL;DR

This paper investigates negative group velocity in layer-by-layer chiral photonic crystals, revealing conditions for negative refraction and proposing feasible structures with computational validation.

Contribution

It introduces a new class of chiral photonic crystals exhibiting negative group velocity, supported by analytical models and computational results.

Findings

Negative group velocity exists in the proposed structures.

Negative refraction depends on interface orientation.

Computational results align with simplified models.

Abstract

We study the group velocity of light in layer-by-layer chiral photonic crystals composed of dielectrics and metals. Through studying the band structures with an extended-zone scheme that is given by a Fourier analysis, we show the existence of negative group velocity in the proposed chiral structures. The physical mechanism is interpreted with the help of a simplified model that has an analytical solution. The iso-frequency contours of the photonic band structure suggest that the negative group velocity can lead to either positive or negative refraction, depending on the orientation of the medium interface. We propose a feasible realization of such kind of photonic crystals. Computational results on the proposed realization are consistent with that of the simplified models.