Soviet Journal of Quantum Electronics

Nondegenerate reversal of polarized light by four-wave interaction in a resonant medium

G. G. Adonts, D G Akopyan

Published Sep 30, 1985• 0 citations

Abstract

The representation of irreducible tensor operators is used to develop a theory of wavefront reversal (WFR) in the absence of saturation effects. This theory deals with arbitrarily polarized waves in a two-level resonant medium having arbitrary angular momenta. It is shown that there are three different physical reversal mechanisms associated with a nonuniform population and with the coherence of the magnetic sublevels in the field. An investigation is made of the influence of the decay times of the polarization moments of the system (the total population, orientation, alignment) on WFR. In particular, it is shown that, subject to specific relationships between the decay times, new collision-induced reversal processes can occur in the presence of deorienting collisions. An investigation is made of the spectral composition of the reflection coefficient of the reversed wave and it is shown that there are various spectral ranges of efficient reversal which in general depend on the polarizations of the interacting waves.

DOI: 10.1070/qe1985v015n09abeh007658

Related papers

Spectral characteristics of light wave reversal in a nondegenerate four-wave interaction in a resonant medium

Pavel A Apanasevich, Anatolii A Afanas'ev, С. П. Жвавый

An investigation is made of wavefront reversal of optical radiation in a nondegenerate four-wave interaction in a resonant medium. It is shown that for a pump intensity comparable with the saturation intensity of the absorption line of the resonant medium, the reversed wave spectrum has two side peaks positioned symmetrically relative to the central peak which corresponds to a degenerate interaction. These side peaks are attributable to regions of negative absorption (amplification) of weak radiation by the resonant medium situated in a high-power field of opposite pump waves. The dependences of the magnitudes and positions of these peaks on the pump intensity can be used to control the spectral and energy characteristics of the reflected radiation. The conditions for self-excitation of a reversing system based on resonant four-wave interaction are determined. In particular, the ranges of the pump intensity and the optical density of the resonant medium in which self-excitation of the reversing system may occur, are determined for a degenerate interaction.

Soviet Journal of Quantum ElectronicsFeb 28, 19830 citations

Polarisation theory of phase conjugation in resonant non-degenerate four-wave mixing

G. G. Adonts, D G Akopyan

The theory of polarised light phase conjugation (PC) in non-degenerate four-wave mixing in a resonant medium has been developed in the irreducible tensorial formalism. The theory is applied to a wave with any polarisation in a resonant medium with levels of arbitrary momentum in the absence of pump-induced saturation effects. The formula for the non-linear susceptibility of the medium has been found and it is shown that the change of the polarisation at PC is essentially connected with the relaxation of the atomic multipole momenta (population, orientation and alignment). Wave equations were investigated for different pump-wave polarisations and three different physical mechanisms of the PC are discussed. The influence of the different relaxation rates of the atomic multipole momenta on the PC reflectivity has been investigated. The spectral dependence of the reflectivity and the spectral ranges which depend on the wave polarisation are found. For motionless atoms with small momenta (J 1 = 1 / 2 to J 2 = 1 / 2 , J 1 =1 to J 2 =0), exact formulae for the non-linear susceptibility of the medium as a function of pump intensity were found. The spontaneous decay of higher level to the lower one was taken into account. Because of optical pumping, saturation effects can be shown at considerably smaller intensities than in the usual two-level system. The exact expressions for the PC reflectivity at different polarisations of the pump waves are given.

Journal of Physics B Atomic and Molecular PhysicsAug 28, 198510 citations

Nonstationary theory of polarized light pulse propagation through a four-level resonant medium with allowance for nonlinear complex refractive index of medium

G. G. Adonts, Mikayel Arzakantsyan

Nonstationary theory of polarized light pulse propagation through the medium with resonant transition 1/2 -1/2 is developed with taking into account complexity of the medium nonlinear refractive index. The theory is developed based on the irreducible tensor formalism which allows diagonalizing relaxations matrix and introducing effective decay times associated with the population relaxation, as well as relaxation of coherence between magnetic sublevels of the resonant system. It is shown that as a result of interference of magnetic sublevels in the polarized radiation field the inversionless amplification of radiation occurs due to optical pumping process. The dependence of inversionless amplification on the line broadening and resonance detuning is studied.

Journal of Contemporary Physics (Armenian Academy of Sciences)Aug 29, 20130 citations

Wavefront reversal of optical beams in resonant media

Nikolai V. Kukhtarev, T. I. Semenets

It is shown that detuning from resonance in resonant media may cause wavefront reversal (WFR) accompanied by rotation. This effect is due to parametric diffraction from phase gratings of the population difference. In resonance, WFR may be found without phase distortions as a result of diffraction from gain gratings in the inverted medium. An analysis is made of the initial stage of the WFR kinetics and the possibility of observing inhomogeneities in WFR is studied.

Soviet Journal of Quantum ElectronicsAug 31, 19803 citations

Nondegenerate four-wave interaction in a resonant medium with Doppler broadening of the absorption line

Anatolii A Afanas'ev, А. П. Войтович, M V Dotsenko

An analysis is made of nondegenerate four-wave interaction (FWI) in a resonant medium (two-level model) with Doppler line broadening allowing for nonlinear absorption of the weak radiation. The cubic approximation with respect to the field is used to derive expressions for the coefficients of parametric coupling and absorption of the mixed waves. The angular dependences of the reflection coefficient are studied for quasicollinear and orthogonal FWI geometries. It is shown that, as a result of the thermal motion of the particles, the dependence of the reflection coefficient on the angle θ between the interacting waves results in considerable limitation of the angular width of the reversed beams. This limitation is greater for degenerate FWI. In the case of nondegenerate FWI, as a result of the selective action of waves on groups of atoms having a specific velocity projection, the reversal efficiency may increase on increase in θ.

Soviet Journal of Quantum ElectronicsMar 31, 19870 citations

Influence of linear absorption and reflection on the characteristics of four-wave wavefront reversal

Boris Ya Zel'dovich, Tatiana Victorovna Yakovleva

An analysis is made of the theory of four-wave wavefront reversal allowing for linear absorption and reflection of all the interacting waves from a mirror which forms a second reference wave from the first incident wave. The Born approximation is used to find the optimum thickness of the nonlinear medium giving the maximum reversal coefficient. Conditions for parametric four-wave oscillation with an arbitrary frequency shift are determined and the dependence of the threshold intensity of the incident reference wave on the linear reflection coefficient of the wave-forming mirror is found for a given thickness of the medium in the absence of absorption.

Soviet Journal of Quantum ElectronicsSep 30, 19812 citations