Experimental observation of wave localization at the Dirac frequency in a two-dimensional photonic crystal microcavity.

Lei Hu,Junxi Zhang,Jianxiang Wen,Haiming Jiang,Kang Xie,Qiuping Mao,Jingjing Chen,Zhijia Hu,Jiangying Xia

doi:10.1364/oe.26.008213

Abstract

Trapping light within cavities or waveguides in photonic crystals is an effective technology in modern integrated optics. Traditionally, cavities rely on total internal reflection or a photonic bandgap to achieve field confinement. Recent investigations have examined new localized modes that occur at a Dirac frequency that is beyond any complete photonic bandgap. We design Al2O3 dielectric cylinders placed on a triangular lattice in air, and change the central rod size to form a photonic crystal microcavity. It is predicted that waves can be localized at the Dirac frequency in this device without photonic bandgaps or total internal reflections. We perform a theoretical analysis of this new wave localization and verify it experimentally. This work paves the way for exploring localized defect modes at the Dirac point in the visible and infrared bands, with potential applicability to new optical devices.

Highlights

Photonic crystals (PCs) are a kind of artificial material composed of periodic dielectric structures
The internal physical mechanism of trapping photons is traditionally attributed to photonic bandgaps or total internal reflections (TIR) [9]
The above discussion explains the appearance of wave localization at the Dirac frequency in the PC, and confirms the algebraic profile of the modes

Summary

Introduction

Photonic crystals (PCs) are a kind of artificial material composed of periodic dielectric structures They have been widely studied due to their theoretical value and engineering applications in recent decades. The Dirac point within the triangular series lattice [10,11,12] photonic band structures has attracted much attention due to the strong similar conical singularities in the electronic band structures of graphene [13]. The diverse approaches for photon capturing lead to an unusual algebraic decay of state and a unique frequency located beyond the bandgaps These modes have not been identified experimentally. Böhm et al [26] demonstrated the implementations of the continuous quantum wave search algorithms and directed wave transport in artificial graphene lattice In this ingenious experiment, localized search states were brought into resonance with an extended lattice state near the Dirac point. This work may lead to new theory and applications of guided waves

Discussion of the problem

Experimental study