Experimental probe of a complete 3D photonic band gap.

Manashee Adhikary,Cornelis A M Harteveld,Ravitej Uppu,Willem L Vos,Diana A Grishina

doi:10.1364/oe.28.002683

Abstract

The identification of a complete three-dimensional (3D) photonic band gap in real crystals typically employs theoretical or numerical models that invoke idealized crystal structures. Such an approach is prone to false positives (gap wrongly assigned) or false negatives (gap missed). Therefore, we propose a purely experimental probe of the 3D photonic band gap that pertains to any class of photonic crystals. We collect reflectivity spectra with a large aperture on exemplary 3D inverse woodpile structures that consist of two perpendicular nanopore arrays etched in silicon. We observe intense reflectivity peaks (R>90%) typical of high-quality crystals with broad stopbands. A resulting parametric plot of s-polarized versus p-polarized stopband width is linear ("y=x"), a characteristic of a 3D photonic band gap, as confirmed by simulations. By scanning the focus across the crystal, we track the polarization-resolved stopbands versus the volume fraction of high-index material and obtain many more parametric data to confirm that the high-NA stopband corresponds to the photonic band gap. This practical probe is model-free and provides fast feedback on the advanced nanofabrication needed for 3D photonic crystals and stimulates practical applications of band gaps in 3D silicon nanophotonics and photonic integrated circuits, photovoltaics, cavity QED, and quantum information processing.

Highlights

Controlling the emission and the propagation of light simultaneously in all three dimensions (3D) remains a major outstanding target in the field of Nanophotonics [1,2,3,4,5]
To arrive at a purely experimental probe of the band gap, we exploit the fact that a 3D photonic band gap is a common gap for both polarizations at all wave vectors in the Brillouin zone simultaneously, cf., Fig. 1(a)
In addition we add a 4th point, namely, we track the stopband widths versus volume fraction to obtain many parametric data points that all agree with the band gap expectation

Summary

Introduction

Controlling the emission and the propagation of light simultaneously in all three dimensions (3D) remains a major outstanding target in the field of Nanophotonics [1,2,3,4,5]. Since the local density of states vanishes in a 3D photonic band gap, the 3D gap is a powerful tool to radically control spontaneous emission and cavity quantum electrodynamics (QED) of embedded quantum emitters [11,12,13,14]. Applications of 3D photonic band gap crystals range from dielectric reflectors for antennae [15] and for efficient photovoltaic cells [16,17,18], via white light-emitting diodes [19], mode and polarization converter [20] to elaborate 3D waveguides [21,22], for 3D photonic integrated circuits [23], to thresholdless miniature lasers [24] and to devices that control quantum noise for quantum measurement, amplification, and information processing [14,25].

Objectives

Results

Discussion

Conclusion