Dependence of Resonant Absorption Linewidth on Atomic Vapour Column Thickness for D1 Line of Cs Atoms Confined in Nano-Cell

TL;DR

This study investigates how the linewidth of resonant absorption in Cs atoms confined in a nano-cell varies with the cell's thickness, revealing conditions for narrowing and broadening of spectral lines at different laser intensities.

Contribution

The paper introduces a nano-cell with variable thickness to systematically study the dependence of absorption linewidths on cell thickness and laser intensity, supported by a theoretical model.

Findings

Narrowing of absorption spectrum at specific thicknesses for low laser intensity.

Broadening of spectrum at other thicknesses and higher intensities.

Observation of velocity selective optical pumping and saturated resonances.

Abstract

A new nano-cell with smoothly varying longitudinal thickness of the atomic vapour layer L in the range of 350 - 5100 nm allowing to study the resonant absorption of D1 and D2 lines of Cs atoms for thicknesses changing from L = Lambda/2 to L = 6 Lambda with the step of Lambda/2 (Lambda = 852 nm or 894 nm are the resonant laser wavelengths) and for different intensities is developed. It is revealed that for low laser intensities there is narrowing of the resonant absorption spectrum for the thicknesses L = (2n + 1)Lambda/2 (where n is an integer) up to L = 7Lambda /2 and broadening of the spectrum for L = n Lambda. For relatively high laser intensity (>1 mW/cm2), velocity selective optical pumping/saturated resonances of a reduced absorption (with the line-width close to the natural one), and centred on the hyperfine transitions occur when L = n Lambda. The possible application of these resonance peaks is given. The developed theoretical model describes well the experiment.