Collective effects in the quantum scattering of radiation

Victor Nikolaevich Popov, Vladimir Sergeevich Yarunin

Valentine P. Oleinik

B. B. Averbukh

It is well known, that for large Rabi frequencies the spectrum of resonance fluorescence of a single two-level atom contains three separate lines (Mollow triplet). Question naturally arise as to what effect sidebands of this triplet might have on the spectrum of the scattered radiation in the multiatom case. The purpose of the present paper, therefore, is to obtain a space-frequency dependent spectrum of the scattered radiation in backward direction (reflection) by a system of N noninteracting atoms. We neglect the translational motion of the atoms and multiple scattering and concentrate on the effects of the collective scattering. It is shown that spectral energy of the scattered radiation consists of two different parts. One is the incoherent and isotropic emission of fluorescence. The energy of radiation in this case is the sum of the atomic energies and then is proportional to N . The other is the collective emission (interference effect). The energy of radiation in this case is spatially focused in a small solid angles about three propagation directions and then is proportional to N2. Thus the frequency Mollow triplet is transformed into the space-frequency dependent triplet.

Fritz Haake

N. A. Enaki

The collective decay effects between the dipole-active three-level subsystems in the nonlinear interaction with dipole-forbidden transitions, like 2 S − 1 S of hydrogen-like radiators, are proposed, taking into consideration the cooperative exchanges between two species of atoms through the vacuum field in the scattering and the two-photon resonance processes. One of them corresponds to the situation when the total energy of the emitted two photons by the three-level radiator in the cascade configuration enters into the two-photon resonance with another type of dipole-forbidden transitions of hydrogen-like (or helium-like) atoms. The similar situation appears in the cooperative scattering between two species of quantum emitters when the difference of the excited energies of the two dipole-active transitions of the three-level radiators is in the resonance with the dipole-forbidden transitions of the Hydrogen-like radiators. These effects are accompanied by the interference between single- and two-quantum collective transitions of the inverted radiators from the ensemble. The two-particle collective decay rate is defined in the description of the atomic correlation functions taking into consideration the phase retardation between them. The kinetic equations which describe the cooperative processes as the function of time and correlation are obtained. The behavior of the system of radiators at short and long time intervals in comparison with the retardation time between them is studied.

I. M. Sokolov, D. V. Kupriyanov, Mark D. Havey

Based on the developed quantum microscopic theory, the interaction of weak electromagnetic radiation with dense ultracold atomic clouds is described in detail. The differential and total cooperative scattering cross sections are calculated for monochromatic radiation as particular examples of application of the general theory. The angular, spectral, and polarization properties of scattered light are determined. The dependence of these quantities on the sample size and concentration of atoms is studied and the influence of collective effects is analyzed.