Loss-difference-induced localization in a non-Hermitian honeycomb photonic lattice

TL;DR

This paper demonstrates light localization in a reconfigurable non-Hermitian honeycomb photonic lattice by inducing absorptive differences that extend Dirac points into flat bands, enabling effective confinement of light.

Contribution

It introduces a novel method to achieve and control light localization using loss-induced flat bands in a non-Hermitian photonic lattice.

Findings

Light localizes at less absorptive lattice sites due to flat band formation.

Loss differences can be tuned to control the extent of localization.

The approach enables reconfigurable and tunable flat band engineering.

Abstract

Non-Hermitian systems with complex-valued energy spectra provide an extraordinary platform for manipulating unconventional dynamics of light. Here, we demonstrate the localization of light in an instantaneously reconfigurable non-Hermitian honeycomb photonic lattice that is established in a coherently-prepared atomic system. One set of the sublattices is optically modulated to introduce the absorptive difference between neighboring lattice sites, where the Dirac points in reciprocal space are extended into dispersionless local flat bands. When these local flat bands are broad enough due to larger loss difference, the incident beam is effectively localized at one set of the lattices with weaker absorption, namely, the commonly seen power exchange between adjacent channels in photonic lattices is effectively prohibited. The current work unlocks a new capability from non-Hermitian two-dimensional photonic lattices and provides an alternative route for engineering tunable local flat bands in photonic structures.