We observe Ramsey fringes in the absorption line shape for a weak optical field probing the transition between an unperturbed quantum state and one that is dynamically Stark shifted by a strong pump field. \textcopyright{} 1996 The American Physical Society.
The dynamic Stark effect (Autler-Townes splitting and radiative shift) of a J = 0 ↔ J = 1 optical transition have been investigated. The barium atomic beam is illuminated by a strong pump beam, resonant or slightly non-resonant with the BaI resonance line (λ = 5 535 Å) ; the fluorescence induced by a weak probe beam is detected versus the probe frequency. With linear polarizations for the two beams one deals either with a two-level (parallel polarizations) or with a three-level system (perpendicular polarizations). In the latter case and for small detunings of the pump beam, the Autler-Townes doublet has been observed. For large detunings of the pump beam a single, shifted resonance has been obtained with both polarization settings. In the three-level case the observation of the passage from the Autler-Townes situation to the light-shift situation, is reported. The corresponding calculations are presented; a particular attention is paid to the case of large detunings for the pump beam (light-shift situation). The evolution calculated for the resonance curve (position and relative intensities of the peaks) when the relative polarization directions are changed is consistent with the experimental data.
In this report, we discussed the interference phenomenon of the AC Stark effect in optical frequency standard with Ramsey spectroscopy. The analytic expression and its numerical result show that an interference fringe is superimposed on the usual AC Stark level shift dispersion line-shape. This phenomenon has never been observed before. By numerical method, we have analyzed the interesting feature of this effect in detail. A method to measure the interference of the AC Stark effect is presented. Finally, a method to observe super-steep dispersion in separated fields scheme is proposed.
We report the observation of the Autler-Townes absorption spectrum of a two-level atom in a 100% amplitude-modulated optical field. Two frequency-stabilized dye lasers interact with a three-level atomic cascade system. One of the two lasers is used to create the bichromatic field that saturates the lower transition, while the second one is tuned in the frequency between the second and third levels to probe the absorption line shape. We investigate the dependence of the spectrum on the detuning between the average frequency of the bichromatic field and the lower atomic resonance. In order to study the effects of saturation, for every value of the detuning we take a series of data for different intensity levels of the bichromatic field. There is very good agreement between theory and experiment and profound differences from the conventional Autler-Townes results with a monochromatic pump field. \textcopyright{} 1996 The American Physical Society.