Doppler-free, two-photon induced coherence and emission

M. M. T. Loy

M. D. Levenson

Nikolay N. Evtikhiev, Задерновский Анатолий Андреевич

Summary form only given. We discuss a way to remove the negative role of chaotic motion of nuclei by ignition of two-quantum induced gamma emission in counterpropagating intense photon beams. Our approach is based on a well known Doppler-free technique used in two-quantum absorption spectroscopy.

Masahiro Matsuoka, Hiroki Nakatsuka, Jumpei Okada

Calcium vapor has been excited by two-photon absorption of a mode-locked dye-laser pulse, and emission from a coherent superposition state of the $4{s}^{2}^{1}S_{0}$ and $4s3d^{1}D_{2}$ levels has been observed using a delayed off-resonant interrogation pulse in the picosecond regime. The emission signal intensity was measured as a function of the delay time of the interrogation pulse, and showed a peak well delayed from that of the dye-laser pulse. This reflects the fact that the induced coherence is expressed by a time integral of the excitation. The emission signal was then found to decay as a result of the Doppler effect. The above process is analyzed by Bloch and Maxwell equations. This is the first reported observation of the coherence of an atomic system induced by two-photon absorption, a coherence which persists after the passage of the excitation pulse and decays inhomogeneously as a result of thermal motion. In carrying out the experiment, deformation of the input dye-laser pulse during propagation through the two-photon resonant medium was carefully avoided.

Bernard Cagnac

G. Grynberg, F. Biraben, M. Bassini +1 more

We report here the first experimental demonstration of Doppler-free three-photon spectroscopy. The Doppler broadening is eliminated by insuring that the sum of the momenta of the three photons simultaneously exchanged between the atom and the laser beams is equal to 0. This is accomplished by making a proper choice of the angles between the three exciting beams. The observation has been made on the sodium $3{S}_{\frac{1}{2}}\ensuremath{-}3{P}_{\frac{1}{2}}$ transition with absorption of two photons and induced emission of one.