Use of an electric-dipole forbidden transition to optically probe the Autler Townes effect

TL;DR

This paper demonstrates how to optically probe the Autler Townes effect in rubidium atoms using a forbidden electric-dipole transition, combining experimental measurements with a detailed theoretical model.

Contribution

It introduces a novel method to study the Autler Townes effect via forbidden electric-dipole transitions in atomic gases, supported by an analytic three-level scheme and experimental validation.

Findings

Observation of Autler Townes splitting via forbidden transition

Good agreement between theoretical model and experimental data

Effective inclusion of Doppler and bandwidth effects in analysis

Abstract

We study the Autler Townes (AT) effect derived from a strong electric dipole transition stimulated by a resonant laser beam and probing it by means of a weak electric quadrupole transition with a controlled frequency detuning in a ladder configuration. The experiment was carried out for a $^{87}$Rb atomic gas at room temperature in a velocity-selective scheme. The AT effect was monitored via the splitting of the fluorescence spectra associated with the spontaneous decay to the ground state. The theoretical description incorporates the modification of standard few-level schemes introduced by forbidden electric-dipole transitions selection rules. We develop an analytic ladder three-level scheme to approximate the cyclic $5\mathrm{S}_{1/2} \mathrm{F}=2\rightarrow 5\mathrm{P}_{3/2} F=3 \rightarrow 6\mathrm{P}_{3/2} \mathrm{F}=1,2,3\rightarrow 5 \mathrm{S}_{1/2}\mathrm{F}=2$ path. Other levels that could have effects on the fluorescence are included via a fourth level with effective parameters. Doppler effects and finite bandwidths of the laser beams are included in the theoretical model to closely reproduce the experimental results.