Strongly Confining Light with Air-Mode Cavities in Inverse Rod-Connected Diamond Photonic Crystals

Mike P C Taverne,John G Rarity,Ying-Lung D Ho

doi:10.3390/cryst12030303

Mike P C Taverne, John G Rarity + Show 1 more

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https://doi.org/10.3390/cryst12030303

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Abstract

Three-dimensional dielectric optical crystals with a high index show a complete photonic bandgap (PBG), blocking light propagation in all directions. We show that this bandgap can be used to trap light in low-index defect cavities, leading to strongly enhanced local fields. We compute the band structure and optimize the bandgap of an inverse 3D rod-connected diamond (RCD) structure, using the plane-wave expansion (PWE) method. Selecting a structure with wide bandgap parameters, we then add air defects at the center of one of the high-index rods of the crystal and study the resulting cavity modes by exciting them with a broadband dipole source, using the finite-difference time-domain (FDTD) method. Various defect shapes were studied and showed extremely small normalized mode volumes (Veff) with long cavity storage times (quality factor Q). For an air-filled spherical cavity of radius 0.1 unit-cell, a record small-cavity mode volume of Veff~2.2 × 10−3 cubic wavelengths was obtained with Q~3.5 × 106.

Highlights

Three-dimensional (3D) photonic crystal microcavities, which are known to have high-quality factors and ultra-small mode volumes (Veff), provide a novel way of trapping light [1,2,3]. Such 3D structures would allow the observation of spontaneous emission modification [4], as well as the investigation of the strong coupling [5] of a small number of quantum emitters in the cavity mode
The enhancement and suppression of spontaneous emission by cavities are useful for single-photon sources, for quantum information processing, while strong coupling allows the creation of all-optical switches, quantum logic gates, and quantum memories using spin-photon entanglement [6]
Most previous research on photonic crystal cavities is based on two-dimensional (2D) photonic crystals for sensors [8,9], while significant work on cavity field enhancement has been performed with a view to coupling with single emitters [10]

Summary

Introduction

Three-dimensional (3D) photonic crystal microcavities, which are known to have high-quality factors (high-Q) and ultra-small mode volumes (Veff), provide a novel way of trapping light (photons) [1,2,3]. Such 3D structures would allow the observation of spontaneous emission modification (via the Purcell effect) [4], as well as the investigation of the strong coupling [5] of a small number of quantum emitters (such as quantum dots or diamond NV-color centers) in the cavity mode.

Results

Conclusion