N.N. Bogolubov

Two-phonon process in a three-level system

Abstract The dynamical behaviour of level filling and occupation numbers of photon modes is examined rigorously. A “quantum expression” for the Rabi frequency is obtained.

Double optical resonance in a system of atoms

Abstract The collective behaviour of N three-level atoms interacting with two resonant driving fields and an emitted field is discussed in the context of double optical resonance. The critical behaviour in the cooperative limit is discussed too.

On the exactly soluble model in quantum electrodynamics

The model of a ladder configuration three-level atom interacting with a two-mode near-resonant radiation field is treated. It is shown that the operator equations of motion can be solved explicitly. The dynamical behaviour of the photon numbers and level populations is studied for various initial conditions.

Exact results for a model of a three-level atom

Abstract For a three-level atom interacting with two modes of the quantized radiation field the time dependence of transition operators, photon amplitudes, and of operators of level populations and photon numbers is examined rigorously. It is shown that the availability of a mode detuning leads to the splitting of the “soft branch” of frequencies of two-photon Rabi oscillations.

Violation of the Cauchy-Schwarz inequality in collective resonánce fluorescence

Abstract The violation of the Cauchy-Schwarz inequality in the collective resonance fluorescence is discussed. The strong violation of this inequality for the two sidebands of the collective fluorescent spectrum is shown.

Collective effects in resonant Raman scattering of intense optical waves

Collective effects in resonant Raman scattering in the presence of intense incident and scattered light waves are investigated. The analytical expressions for the steady-state spectrum and normalised intensity correlation functions for components of the spectra are given. In the cooperative limit N to infinity the relative intensities and normalised intensity correlation functions for each component of the spectra have a discontinuous behaviour reminiscent of a typical non-equilibrium first-order phase transition.

Superradiance allowing for the pumping processes

An exact kinetic equation for a three-level macroscopic system interacting with an electromagnetic field is obtained taking into account the coherent pumping processes. On its basis the collective spontaneous radiation of the system is examined in the markovian limit. The relations between the parameters of the supperadiant pulse and those of the pumping pulse are obtained.

Photon statistics and atomic dynamics in a three-level plus two-mode model

Abstract The relations between photon statistical characteristics and atomic level populations are examined rigorously. The characteristic and photon distribution functions are found.

On the kinetics of Dicke-type systems

An exact hierarchy for the Dicke-type model problems is obtained. On its basis spontaneous-radiation processes are examined.

Statistical properties of photons in collective resonance fluorescence

The photon statistics of spectrum components and the cross correlation between spectrum components in resonance fluorescence are discussed. For the collective case anticorrelation between the central component and the sidebands is observed.