Three-dimensional single gyroid photonic crystals with a mid-infrared bandgap

TL;DR

This paper reports the design, fabrication, and characterization of amorphous silicon gyroid photonic crystals with a complete mid-infrared bandgap, demonstrating precise control over their optical properties through a novel synthesis approach.

Contribution

It introduces a new method for creating 3D gyroid photonic crystals with tailored mid-infrared bandgaps using two-photon lithography and material deposition.

Findings

Achieved 100% reflectance at 7.5 μm for specific gyroid structures

Confirmed bandgap positions match electromagnetic simulation predictions

Demonstrated control over bandgap by adjusting unit cell size

Abstract

A gyroid structure is a distinct morphology that is triply periodic and consists of minimal isosurfaces containing no straight lines. We have designed and synthesized amorphous silicon (a-Si) mid-infrared gyroid photonic crystals that exhibit a complete bandgap in infrared spectroscopy measurements. Photonic crystals were synthesized by deposition of a-Si/Al2O3 coatings onto a sacrificial polymer scaffold defined by two-photon lithography. We observed a 100% reflectance at 7.5 \mum for single gyroids with a unit cell size of 4.5 \mum, in agreement with the photonic bandgap position predicted from full-wave electromagnetic simulations, whereas the observed reflection peak shifted to 8 um for a 5.5 \mum unit cell size. This approach represents a simulation-fabrication-characterization platform to realize three-dimensional gyroid photonic crystals with well-defined dimensions in real space and tailored properties in momentum space.