Effect of the light wavefront on polarization of a molecule in a strong resonance field

José Luis Arce Diego, Félix Fanjul-Vélez, David Pereda Cubián +3 more

The potentialities of diffraction methods for wavefront transformations may be considerably widened due to the use of nonlinear recording of dynamic holograms enabling multiwave mixing in media with the fifth and higher order nonlinearities. There is a great variety of such media including the resonant ones for which the presence of higher order nonlinearities is conditioned by the absorption saturation effect and transitions between different excited states of the molecules. However, in the majority of previous studies of multiwave mixing the resonant medium approximation has been used disregarding the induced anisotropy effect. This work presents a theoretical model and experimental studies of the energy efficiency of multiwave mixing in complex molecular media exhibiting higher order nonlinearities, in two cases: when the nonlinear cavity is introduced in the Fabry-Perot interferometer (IFP), and without it. Owing to the use of different combinations of mutually aligning polarizations for interacting waves, one is enabled to determine the contribution into the interaction efficiency by various dynamic gratings and nonlinearity mechanisms. The role of polarization gratings resultant from spatial modulation of the light field polarization state at the orthogonal polarization of the hologram recording waves has been established. Comparisons between the contributions of the above gratings and “normal” gratings recorded by identically polarized light beams into the process of multiwave mixing have demonstrated that the relation of these contributions is dependent on the intensity of interacting waves, and also it has been found that polarization of the diffracted wave is dependent on the diffraction order.

Yu. T. Mazurenko, Vladimir Sergeevich Yarunin

Nikolai I. Pavlov, A. A. Kiselev, A. V. Lyaptsev

G. G. Adonts, D G Akopyan

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.

G. A. Vugalter, Alexey V. Shvetsov

The effect of electromagnetically induced transparency in crystals of magnetic molecules was theoretically investigated. The problem of choosing the polarizations of strong and weak resonant magnetic fields acting on a crystal is discussed. Estimates of the amplitude of strong resonant field that is necessary for manifestation of this effect in crystals of magnetic molecules Mn 12 and Fe 8 are reported.

Frank A. Novak