Infiltrating a thin or single layer opal with an atomic vapour: sub-doppler signals and crystal optics

TL;DR

This paper investigates the optical properties of thin or single-layer artificial opals infiltrated with resonant alkali vapour, revealing sub-Doppler signals and crystal anisotropy through experimental and modeling approaches.

Contribution

It extends previous work by analyzing sub-Doppler resonant signals in ultra-thin opal layers and develops models to predict their optical behavior and anisotropy.

Findings

Sub-Doppler structures observed in thin opal infiltrations.

The layered optical model accurately predicts lineshape variations.

Crystalline anisotropy demonstrated via diffraction in single-layer opals.

Abstract

Artificial thin glass opals can be infiltrated with a resonant alkali-metal vapour, providing novel types of hybrid systems. The reflection at the interface between the substrate and the opal yields a resonant signal, which exhibits sub-Doppler structures in linear spectroscopy for a range of oblique incidences. This result is suspected to originate in an effect of the three-dimensional confinement of the vapour in the opal interstices. It is here extended to a situation where the opal is limited to a few or even a single layer opal film, which is a kind of bidimensional grating. We have developed a flexible one-dimensional layered optical model, well suited for a Langmuir-Blodgett opal. Once extended to the case of a resonant infiltration, the model reproduces quick variations of the lineshape with incidence angle or polarization. Alternately, for an opal limited to a single layer of identical spheres, a three-dimensional numerical calculation was developed. It predicts crystalline anisotropy, which is demonstrated through diffraction on an empty opal made of a single-layer of polystyrene spheres.