Resonant infiltration of an opal: reflection lineshape and contribution from in-depth regions

TL;DR

This paper investigates how resonant infiltration affects the optical reflection of artificial opals, revealing that the response oscillates with infiltration depth and depends on incidence angle and polarization, indicating deep infiltration effects.

Contribution

It introduces a stratified effective index model to analyze resonant infiltration effects and demonstrates the spatial oscillation of the resonant response with infiltration position.

Findings

Resonant response oscillates with infiltration depth.

Reflection shape varies sharply with incidence angle and polarization.

Deep infiltration influences the global optical response.

Abstract

We analyze the resonant variation of the optical reflection on an infiltrated artificial opal made of transparent nanospheres. The resonant infiltration is considered as a perturbation in the frame of a previously described one-dimensional model based upon a stratified effective index. We show that for a thin slice of resonant medium, the resonant response oscillates with the position of this slice. We derive that for adequate conditions of incidence angle, this spatially oscillating behavior matches the geometrical periodicity of the opal, and hence the related density of resonant infiltration. Close to these matching conditions, the resonant response of the global infiltration varies sharply in amplitude and shape with the incidence angle and polarization. The corresponding resonant reflection originates from a rather deep infiltration, up to several wavelengths or layers of spheres. Finally, we discuss the relationship between the present predictions and our previous observations on an opal infiltrated with a resonant vapor.