Investigation of defect cavities formed in three-dimensional woodpile photonic crystals

TL;DR

This paper optimizes the optical properties of defect cavities in 3D woodpile photonic crystals using computational methods, achieving high Q-factors and small mode volumes to enhance light-matter interactions.

Contribution

It introduces a systematic optimization of defect cavities in 3D woodpile photonic crystals, demonstrating high Q-factors and small mode volumes for potential quantum applications.

Findings

Achieved Q-factors up to 700,000.

Realized cavity volumes below 0.2 (λ/n)^3.

Enhanced spontaneous emission and strong coupling potential.

Abstract

We report the optimisation of optical properties of single defects in three-dimensional (3D) face-centred-cubic (FCC) woodpile photonic crystal (PC) cavities by using plane-wave expansion (PWE) and finite-difference time-domain (FDTD) methods. By optimising the dimensions of a 3D woodpile PC, wide photonic band gaps (PBG) are created. Optical cavities with resonances in the bandgap arise when point defects are introduced in the crystal. Three types of single defects are investigated in high refractive index contrast (Gallium Phosphide-Air) woodpile structures and Q-factors and mode volumes ($V_{eff}$) of the resonant cavity modes are calculated. We show that, by introducing an air buffer around a single defect, smaller mode volumes can be obtained. We demonstrate high Q-factors up to 700000 and cavity volumes down to $V_{eff}<0.2(\lambda/n)^3$. The estimates of $Q$ and $V_{eff}$ are then used to quantify the enhancement of spontaneous emission and the possibility of achieving strong coupling with nitrogen-vacancy (NV) colour centres in diamond.