Line Shape of Two-Photon Absorption in a Standing-Wave Field in a Gas

M. S. Pindzola

Kevin K. Lehmann

A weak excitation transit-time resolution limited analytic line shape is derived for a Doppler broadening-free degenerate two-photon transition from a standing wave with a TEM00 transverse profile. This approximation is appropriate when the collisional mean free path is much larger than the transverse width of the TEM00 beam. It is considerably simpler than the two-photon absorption line shape previously published, Bordé, C. R. Hebd. Seances Acad. Sci., Ser. B 282, 341–344 (1976), which was derived for more general experimental conditions. The case of a saturating field, with an intensity-dependent shift of the resonance frequency, is treated and expressed in reduced units. Numerical calculations are presented for the line shape for a range of the reduced intensity and light intensity shifts values.

Moorad Alexanian, S. Bose

E. V. Baklanov, B Ya Dubetskiĭ

An analysis is made of the influence of transit effects on the profile of a two-absorption line of a gas interacting with a standing wave field. It is shown that in the case of a confined light beam the resonance width is governed by the transit times of atoms across the beam. When two light beams separated by a large distance are present, there is an additional resonance line of width which is the reciprocal of the transit time between the beams. This resonance is analyzed allowing for the relaxation of atomic levels.

Gerard Nienhuis

F. Biraben, Bernard Cagnac, G. Grynberg

Experiments on the $3S\ensuremath{-}5S$ two-photon transition in sodium give evidence that Doppler broadening is eliminated if the atom absorbs two photons propagating in opposite directions. The proof is given by the comparison of the two-photon absorption line shape in traveling and standing waves.