Flat-band localization and self-collimation of light in photonic crystals

TL;DR

This paper explores how flat bands in a quasi-one-dimensional photonic crystal lead to light localization and self-collimation, with potential applications in controlling light propagation.

Contribution

It demonstrates the existence of flat bands causing localized states and self-collimation in a specific photonic crystal structure using FDTD simulations.

Findings

Flat bands cause localized light states due to destructive interference.

Self-collimation occurs at the flat-band frequency along a specific direction.

Flat bands are nondispersive along one axis and dispersive along another.

Abstract

We investigate the optical properties of a photonic crystal composed of a quasi-one-dimensional flat-band lattice array through finite-difference time-domain simulations. The photonic bands contain flat bands (FBs) at specific frequencies, which correspond to compact localized states as a consequence of destructive interference. The FBs are shown to be nondispersive along the $\Gamma\rightarrow X$ line, but dispersive along the $\Gamma\rightarrow Y$ line. The FB localization of light in a single direction only results in a self-collimation of light propagation throughout the photonic crystal at the FB frequency.