Absolute absorption on the rubidium D₁line including resonant dipole–dipole interactions

Abstract

Here we report on measurements of the absolute absorption spectra of dense rubidium vapour on the D1 line in the weak-probe regime for temperatures up to 170• C and number densities up to 3 × 10 14 cm −3 . In such vapours, modifications to the homogeneous linewidth of optical transitions arise due to dipole-dipole interactions between identical atoms, in superpositions of the ground and excited states. Absolute absorption spectra were recorded with deviation of 0.1% between experiment and a theory incorporating resonant dipole-dipole interactions. The manifestation of dipole-dipole interactions is a self-broadening contribution to the homogeneous linewidth, which grows linearly with number density of atoms. Analysis of the absolute absorption spectra allow us to ascertain the value of the self-broadening coefficient for the rubidium D1 line: β/2π = (0.69 ± 0.04) × 10 −7 Hz cm 3 , in excellent agreement with the theoretical prediction.

Shifts of a Resonance Line in a Dense Atomic Sample

“…Optical experiments in dense samples [5,8,11] have shown good agreement with theory [4]. Our fitted value Γ varies somewhat with the thickness of the sample, but is in the neighborhood of Γ ∼ 17γ.…”

“…If the polarizability has a Lorentzian line shape then so does the susceptibility, but the resonance is shifted by what is known as the Lorentz-Lorenz (LL) shift [3]. The LL shift serves as the generic frequency scale for other density dependent phenomena in an atomic sample such as collisional self-broadening of absorption lines [4,5] and collective Lamb shift (CLS) [6][7][8][9][10].Local-field corrections are a standard workhorse in solid and liquid media. On the other hand, in a resonant atomic gas a density conducive to LL shift and CLS results in an optically thick sample, which might explain the sparsity of laser spectroscopy era experiments.…”

Photons and Atoms Cooperate, Virtually

“…To illustrate this, we also plot the theoretical prediction with the line shift removed. From fitting the data, the collisional broadening is found to be 3 for thicknesses greater than =4 in agreement with previous work (see [23] and references therein). For thicknesses shorter than =4, we observe additional broadening that requires further investigation.…”

“…For a gaseous ensemble, atomic motion leads to collisions that also contribute a density dependent shift Á col and broadening À self of the resonance lines (see [23] and references therein), and thus the total shift for a thermal ensemble becomes…”

Coupling Thermal Atomic Vapor to Slot Waveguides

“…The density dependence of the Lorentzian width is plotted in part (a) and shows a nearly linear increase with the growing number density. This behavior is attributed to a self-broadening contribution to the homogeneous linewidth due to resonant dipole-dipole interactions [44,45]. Assuming this, the total Lorentzian width is given by Γ tot ¼ Γ þ Γ TT þ βN , where Γ TT is the transit time broadening, β is the self-broadening coefficient, and N is the number density.…”