We present the results of a computer experiment designed to investigate the effect of chirp on the amplitude of the solitons produced in resonant media by incident coherent optical pulses. Comparison is made to the predictions derived from higher conservation laws.
Higher conservation laws associated with the phase-dependent Maxwell-Bloch equations are derived and employed to determine both amplitudes and frequency shifts of the final-state solitons produced in a resonant medium by an initially phase-modulated optical pulse of area $<5\ensuremath{\pi}$. The higher conservation laws are shown to provide a relatively efficient method of relating the parameters of the final pulses to those of the incident pulse. Connection is made to the computer work of Diels and Hahn.
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.
We report the coherent propagation of optical pulses through a three-level atomic system embedded in a nonlinear dispersive waveguide. We treat the case where an initially chirped soliton in resonance with the pump transition propagates together with a seed without chirp in resonance with the Stokes transition. It is found that the initial chirp is suppressed during the soliton frequency conversion, demonstrating the principle of a frequency converter that produces chirp-free soliton pulses. Numerical solutions of the complete equation set describing our system corroborate our analytical result.
If an incident pulse is chirped, the critical parameters for self-induced transparency to occur in coherent pulse propagation can no longer be obtained from the well-known McCall-Hahn area theorem. We have been able to obtain these parameters by solving the Zakharov-Shabat eigenvalue equation for the bound-state eigenvalues. We find that critical (threshold) areas will be increased for a chirped incident pulse in almost all cases, except for a box profile or for a pulse that is approximately box-like in shape. In these latter cases, the chirped critical areas will instead decrease for the second and all higher branches. The first branch’s critical area is always increased due to chirping.
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.