Complete photonic band gaps in 3D foams

TL;DR

This paper demonstrates, through numerical simulations and experimental techniques, that FCC foam structures can achieve complete 3D photonic band gaps in the visible spectrum using standard fabrication methods.

Contribution

It introduces a new approach to create 3D photonic band gaps in the visible range using FCC foam structures with practical fabrication pathways.

Findings

FCC foams can open complete band gaps at 500 nm.

Monodisperse solid Kepler foams were successfully produced.

A feasible pathway for downsizing foams to 400 nm was presented.

Abstract

To-date, despite remarkable applications in optoelectronics and tremendous amount of theoretical, computational and experimental efforts, there is no technological pathway enabling the fabrication of 3D photonic band gaps in the visible range. The resolution of advanced 3D printing technology does not allow to fabricate such materials and the current silica-based nanofabrication approaches do not permit the structuring of the desired optical material. Materials based on colloidal self-assembly of polymer spheres open 3D complete band gaps in the infrared range, but, owing to their critical index, not in the visible range. More complex systems, based on oriented tetrahedrons, are still prospected. Here we show, numerically, that FCC foams (Kepler structure) open a 3D complete band gap with a critical index of 2.80, thus compatible with the use of rutile TiO2. We produce monodisperse solid Kepler foams including thousands of pores, down to 10 um, and present a technological pathway, based on standard technologies, enabling the downsizing of such foams down to 400 nm, a size enabling the opening of a complete band gap centered at 500 nm.