Optics of an opal modeled with a stratified effective index and the effect of the interface

TL;DR

This paper presents a stratified effective index model to describe the optical reflection and transmission in artificial opals, accounting for interface effects and light scattering, with validation against experimental data.

Contribution

The paper introduces a stratified medium model based on a one-dimensional effective index variation, specifically addressing interface effects in artificial opals and extending applicability to various photonic structures.

Findings

Interface regions significantly affect reflection away from Bragg peaks

Model accurately predicts experimental reflection and transmission data

Effective index stratification simplifies complex photonic crystal analysis

Abstract

Reflection and transmission for an artificial opal are described through a model of stratified medium based upon a one-dimensional variation of an effective index. The model is notably applicable to a Langmuir-Blodgett type disordered opal. Light scattering is accounted for by a phenomenological absorption. The interface region between the opal and the substrate -or the vacuum- induces a periodicity break in the photonic crystal arrangement, which exhibits a prominent influence on the reflection, notably away from the Bragg reflection peak. Experimental results are compared to our model. The model is extendable to inverse opals, stacked cylinders, or irradiation by evanescent waves