Tight-binding photonic bands in metallophotonic waveguide networks and flat bands in kagome lattices

TL;DR

This paper demonstrates the realization of tight-binding photonic bands in metallophotonic networks, introduces flat bands in kagome lattices with extremely slow group velocities, and shows potential for designing novel photonic materials.

Contribution

It introduces a new approach to create tight-binding photonic bands using metallophotonic waveguide networks and proposes flat bands in kagome lattices for slow light applications.

Findings

Photonic bound states form tight-binding bands at network crossings.

Low-lying photon dispersions are accurately described by tight-binding models.

Flat photonic bands with group velocities as low as 1/1000 of light speed are achievable.

Abstract

We propose that we can realize "tight-binding photonic bands" in metallophotonic waveguide networks, where the photonic bound states localized around the crossings of a network form a tight-binding band. The formation of bound states at the crossings is distinct from the conventional bound states at defects or virtual bound states in photonic crystals, but comes from a photonic counterpart of the zero-point states in wave mechanics. Model calculations show that the low-lying photon dispersions are indeed described accurately by the tight-binding model. To exemplify how we can exploit the tight-binding analogy for a {\it designing} of photonic bands, we propose a "flat photonic band" in the kagome network, in which the photonic flat band is shown to arise with group velocities that can be as small as 1/1000 times the velocity of light in vacuum.