Design of full-k-space flat bands in photonic crystals beyond the tight-binding picture.

Changqing Xu,C T Chan,Yun Lai,Jie Luo,Gang Wang,Zhi Hong Hang

doi:10.1038/srep18181

Abstract

Based on a band engineering method, we propose a theoretical prescription to create a full-k-space flat band in dielectric photonic crystals covering the whole Brillouin Zone. With wave functions distributed in air instead of in the dielectrics, such a flat band represents a unique mechanism for achieving flat dispersions beyond the tight-binding picture, which can enormously reduce the requirement of permittivity contrast in the system. Finally, we propose and numerically demonstrate a unique application based on the full-k-space coverage of the flat band: ultra-sensitive detection of small scatterers.

Highlights

Based on a band engineering method, we propose a theoretical prescription to create a full-k-space flat band in dielectric photonic crystals covering the whole Brillouin Zone
One possible route to realize slow light is the creation of flat bands in photonic crystals[2,3,4,5,6,7,8,9,10,11,12,13,14,15], which exhibit dramatically small group velocities and high density of states (DOS), and provide an efficient method to slow down and control photons
In order to expand the range of the flat bands so as to cover the whole Brillouin Zone, the conventional wisdom is to make the wave functions in the photonic crystal more localized in space

Summary

Introduction

Based on a band engineering method, we propose a theoretical prescription to create a full-k-space flat band in dielectric photonic crystals covering the whole Brillouin Zone. In the typical band structures of photonic crystals, flat bands usually only appear in a small region in k-space, such as the Brillouin zone edge or center[16,17,18,19,20,21,22,23].

Results

Conclusion