Measurement and modelization of silica opal optical properties

Amaury Avoine,Laurent Coolen,Agnès Maître,Kifle Aregahegn,Bruno Gallas,Paul Bénalloul,Catherine Schwob,Hugo Frederich,Pham Thu Nga,Phan Ngoc Hong

doi:10.1088/2043-6262/5/1/015005

Abstract

We present the synthesis process and optical characterization of artificial silica opals. The specular reflection spectra are analyzed and compared to band structure calculations and finite difference time domain (FDTD) simulations. The silica optical index is a key parameter to correctly describe an opal and is usually not known and treated as a free parameter. Here we propose a method to infer the silica index, as well as the silica spheres diameter, from the reflection spectra and we validate it by comparison with two independent infrared methods for the index and, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the spheres diameter.

Highlights

Artificial opals are stackings of sub-micrometer dielectric spheres ordered in a compact crystallographic structure
The spheres diameter inferred from measurements on these images of the surface periodicity is equal to 330 ± 10 nm
The results summarized in table 1 show the good agreement between the method we developed to extract the opal effective index and the spheres diameter from the reflection spectra and other independent methods (IR ellipsometry and spectroscopy for the index, scanning electron microscopy (SEM) and atomic force microscopy (AFM) measurements for the diameter)

Summary

Introduction

Artificial opals are stackings of sub-micrometer dielectric spheres ordered in a compact crystallographic structure. They can be synthetized by various protocols of selforganization [1, 2]. They provide versatile and cost-efficient three-dimensional photonic crystals, and thereby present bands of forbidden light propagation [1, 3]. The dependence of the wavelength of these stop bands as a function of the considered propagation direction can be treated in two ways. A second way is to model the opal by a lattice of scattering

Methods

Results

Conclusion