Propagation dynamics of nonlinear chirped optical laser pulses in a two-level medium

Valerică Ninulescu, Andreea-Rodica P. Sterian

Haifeng Yao Haifeng Yao, Yueping Niu Yueping Niu, Yandong Peng +1 more

We investigate the propagation dynamics of nonlinear chirped optical laser pulses in a two-level medium.For certain chirp strength and chirp width, an incident 2π nonlinear chirped pulse will split into optical precursors and a stable self-induced transparency soliton.This is caused by the particular Fourier spectrum that includes not only central resonant frequency components but also high-frequency and low-frequency sidebands.Moreover, the effects of chirp parameters on the evolution of nonlinear chirped pulses are also discussed.

J Zhang

Recently, the advances in generation and characterization techniques of ultrashort laser pulses made it practical to prepare precisely defined laser pulses, these open up new possibilities for studying and controlling dynamical processes in femtosecond time scale. Hitherto, frequency-synthesized or chirped laser pulses have been widely applied to high-order harmonic generation (HHG) [3], population transfer [4], multiphoton transitions between Rydberg states [5], ect. Both the interference of two-color pulses and the nontrivial time dependence of chirped pulse laser field may lead to very interesting results. Moreover, recent studies have manifested that chirping can also have much impacts on the laser pulses as it propagates through different medium. For example, the propagation properties of chirped soliton pulses in optical nonlinear Kenmedia were investigated by Desaix et al. [6]. The result indicates that the properties of asymptotically emerging solitons depend not only on the magnitude, but also on the form of the initial chirp. In particular, the splitting of an initial pulse into separating soliton pulse pairs only occurs for certain classes of initial chirp functions. The influence of pulse shape and frequency chirp on stability of optical solitons was studied by Klaus and Shaw [7]. They found that destabilization occurs when eigenvalues of an associated Zakharov-Shabat system, which move along the positive imaginary axis with increasing chirp parameter, either are absorbed into the lower half plane or collide with a nother eigenvalue. Furthermore, the signal and group velocities for chirped pulses propagating through a GaAs cavity were measured by Centini et al. [8]. They showed that the chirp substantially modifies the group velocity of the pulse, but leaves the signal velocity unaltered.

Szczepan Chelkowski, André D. Bandrauk

G. Demeter, David Dzsotjan, Gagik P. Djotyan

We study the propagation of frequency-chirped laser pulses in optically thick media. We consider a medium of atoms with a $\ensuremath{\Lambda}$ level-scheme (Lambda atoms) and also, for comparison, a medium of two-level atoms. Frequency-chirped laser pulses that induce adiabatic population transfer between the atomic levels are considered. They induce transitions between the two lower (metastable) levels of the $\ensuremath{\Lambda}$-atoms and between the ground and excited states of the two-level atoms. We show that associated with this adiabatic population transfer in $\ensuremath{\Lambda}$-atoms, there is a regime of enhanced transparency of the medium---the pulses are distorted much less than in the medium of two-level atoms and retain their ability to transfer the atomic population much longer during propagation.

Vasily G. Arkhipkin, Д. В. Манушкин, V. P. Timofeev