Optical anisotropy induced by light pulse in a two-level medium with a relaxing excited state

S. E. Kumekov

M. H. Hovhannisyan

Abilities of the method of accumulation of coherent unstable response of a medium for amplification of the rotated component of the probe wave’s polarization in the atomic medium of three-level atoms are studied. Probe wave is examined in frames of the perturbation theory and its frequency is considered near to one photon resonance from the ground to the first excited level. The intense monochromatic pump field connects two excited energy levels and propagates through the medium without a change. The broadening of spectral lines caused by the relaxation processes and the Doppler broadening are included into the calculations. It is shown that by multiple consistent instantaneous change of input probe field’s phase from 0 to π and back, it is possible to obtain, in the tail part of the rotated component of the probe field, a separate narrowed light pulse along with the increase in intensity by more than an order of magnitude with respect to the input field.

Mikhail D. Tokman, Maria Erukhimova

V. R. Nagibarov, I. A. Nagibarova, N. K. Solovarov +1 more

An analysis is made of the evolution of a light pulse in a two-level resonant medium as a function of the degree of preliminary excitation by another pulse. It is shown that, in addition to self-induced transparancy observed under certain conditions associated with the degree of excitation of the atomic system, resonance scattering is also found due to the existence of macroscopic polarization of the medium. This scattering is not observed when the medium is in a noncoherent state. The transverse reversible relaxation time T * 2 can be determined from the variation of the scattering intensity.

B. M. Arutyunyan, A. Zh. Muradyan, L. Petrosyan

Y. B. Band

We consider the nonlinear propagation of an intense short pulse of polarized light through a molecular medium with ground- and excited-state absorption, excited-state emission, and fluorescence from the excited state to the ground state and possibly to a lower-lying excited state. We incorporate the effects of saturation, field-induced alignment, and rotational diffusion of the molecules in the medium. Our approach uses a slowly varying envelope approximation for the light propagation and rate equations for the effective parallel and perpendicular (and higher-multipole) population components of the molecular states. The time dependence of the anisotropy of the fluorescence occurring after preparation of the medium by the intense short pulse is determined. We can treat propagation through an optically nonthin medium wherein the intensity of the pulse decreases while propagating through the medium. An example of a 100-ps pulse propagating through a sample of Rhodamine-6G is presented. We compare our method with others used to describe intense-short-pulse propagation in molecular media.