Abstract:
The conclusions of a theoretical study of the joint propagation in a resonant medium of two laser pulses with the same input intensity and envelope shape are reported. The resonant medium is modeled by the $\Lambda$-scheme of inhomogeneously broadened quantum transitions between degenerate levels $^3P_0$, $^3P^0_1$ and $^3P_2$ of the $^{208}$Pb isotope. Cases of opposite and identical directions of circular polarizations of input fields are considered. It is shown that the process of pulse propaga-tion is accompanied by a transfer of energy from the high-frequency component of the radiation, resonant with the transition between the lower and upper energy levels of the $\Lambda$-scheme, into the low-frequency component, resonant with the transition between excited levels and of the $\Lambda$-scheme. The high-frequency component in the case of different directions of circular polarizations of the input pulses propagates in the medium over a much greater distance than in the case of identical directions of circular polarizations of these pulses. During propagation, the pulse intensity envelopes are distorted, and in the case of opposite circular polarizations of the input pulses, the deformation of the envelopes is noticeably less than in the case of the same polarization directions of these pulses. In all cases, when pulses propagate, trains of short subpulses of significant intensity appear at their trailing edges. In the case of opposite directions of circular polarizations of the input fields, both radiations retain the original circular polarization in the medium and are devoid of phase modulation. However, in the case of identical directions of circular polarization of the input pulses, their radiation in the medium represents elliptically polarized waves with a variable eccentricity of the polarization ellipse and the presence of phase modulation.
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