Observation of light propagation through a three-dimensional cavity superlattice in a 3D photonic band gap

TL;DR

This study demonstrates the experimental observation of light propagation through a 3D superlattice of resonant cavities within a photonic band gap, revealing potential for advanced 3D photonic applications.

Contribution

It provides the first experimental evidence of 3D cavity superlattice bands in a silicon photonic crystal with a broad band gap, showing how cavities couple in three dimensions.

Findings

Observation of narrow spectral features matching superlattice bands

Cavities are coupled in all three dimensions when closely spaced

Light hops in high symmetry directions, enabling 3D photonic networks

Abstract

We experimentally investigate unusual light propagation inside a three-dimensional (3D) superlattice of resonant cavities that are confined within a 3D photonic band gap. Therefore, we fabricated 3D diamond-like photonic crystals from silicon with a broad 3D band gap in the near-infrared and doped them with a periodic array of point defects. In position-resolved reflectivity and scattering microscopy, we observe narrow spectral features that match well with superlattice bands in band structures computed with the plane wave expansion. The cavities are coupled in all three dimensions when they are closely spaced and uncoupled when they are further apart. The superlattice bands correspond to light that hops in high symmetry directions in 3D - so-called Cartesian Light - that opens applications in 3D photonic networks, 3D Anderson localization of light, and future 3D quantum photonic networks.