Observation of Ground and Excited Flat Band States in Graphene Photonic Ribbons

TL;DR

This paper reports the experimental observation of flat band states in a photonic graphene ribbon, demonstrating non-diffracting propagation of fundamental and dipolar modes, and enabling photonic emulation of higher orbital dynamics.

Contribution

The first experimental realization of flat band states in a photonic graphene ribbon supporting multiple flat bands and their non-diffracting propagation.

Findings

Observation of two sets of flat bands in photonic graphene ribbons

Successful excitation and demonstration of non-diffracting propagation of flat band modes

Potential for photonic emulation of higher orbital dynamics

Abstract

Understanding the wave transport and localisation is a major goal in the study of lattices of different nature. In general, inhibiting the energy transport on a perfectly periodic and disorder-free system is challenging, however, some specific lattice geometries allow localisation due to the presence of dispersionless (flat) bands in the energy spectrum. Here, we report on the experimental realisation of a quasi-one-dimensional photonic graphene ribbon supporting four flat-bands. We study the dynamics of fundamental and dipolar modes, which are analogous to the s and p orbitals, respectively. In the experiment, both modes (orbitals) are effectively decoupled from each other, implying two sets of six bands, where two of them are completely flat. Using an image generator setup, we excite the s and p flat band modes and demonstrate their non-diffracting propagation for the first time. Our results open an exciting route towards photonic emulation of higher orbital dynamics.