Symmetry Breaking in Photonic Crystals: On-Demand Dispersion from Flatband to Dirac Cones

TL;DR

This paper introduces a method to control the energy-momentum dispersion in photonic crystals by symmetry breaking, enabling on-demand tuning from flatbands to Dirac cones, with experimental validation of dispersion transformations.

Contribution

It presents a general theoretical framework and experimental demonstration for on-demand dispersion tuning in photonic crystals through symmetry breaking.

Findings

Symmetry breaking enables tuning of local density of states from zero to infinity.

Experimental transformation of a photonic band from quadratic to Dirac, flat, and multivalley dispersions.

Provides a new degree of freedom for optical dispersion engineering.

Abstract

We demonstrate that symmetry breaking opens a new degree of freedom to tailor the energy-momentum dispersion in photonic crystals. Using a general theoretical framework in two illustrative practical structures, we show that breaking symmetry enables an on-demand tuning of the local density of states of a same photonic band from zero (Dirac cone dispersion) to infinity (flatband dispersion), as well as any constant density over an adjustable spectral range. As a proof-of-concept, we experimentally demonstrate the transformation of a very same photonic band from conventional quadratic shape to Dirac dispersion, flatband dispersion and multivaley one, by finely tuning the vertical symmetry breaking. Our results provide an unprecedented degree of freedom for optical dispersion engineering in planar integrated photonic devices.