The spectra of two-color few-cycle pulses in a two-level medium are investigated by solving the full Maxwell-Bloch equations. It is shown that the spectra depend crucially on the relative phase /spl phi/ of the two pulses.
Using a $\ensuremath{\omega}\ensuremath{-}2\ensuremath{\omega}$ combination scenario, we investigate the spectra of two-color ultrashort laser pulses in a two-level medium. It is found that higher spectral components can be produced even for small area pulses due to the interference effect of the two laser pulses. Moreover, these higher spectral components depend crucially on the relative phase $\ensuremath{\varphi}$ of the two laser pulses: continuum and distinct peaks can be achieved through the control of the relative phase.
Using the full Maxwell-Bloch equations which avoid the limitations of slowly-varying-envelope approximation and the rotating--wave approximation as ultrashort pulses are considered, we investigate the coherent control of spectra effects with two color few-cycle laser pulses. We demonstrate that the interference effect of the two laser pulses can substantially modify the behavior of the spectra, higher spectral components can occur even for small area pulses. Moreover, comparing the ω-2ω combination with the ω-3ω scenario, we find due to the deferent superposition of the two kinds of combined laser pulses, the features of these higher spectral components can be much different.
A theoretical investigation on the coherent control of optical transient four-wave mixing interactions in two-level systems with two intense few-cycle propagating laser pulses of central angular frequencies $\ensuremath{\omega}$ and $3\ensuremath{\omega}$ is reported. By numerically solving the full Maxwell-Bloch equations beyond the slowly varying envelope and rotating-wave approximations in the time domain, the nonlinear coupling to the optical field at frequency $5\ensuremath{\omega}$ is found to depend critically on the initial relative phase $\ensuremath{\phi}$ of the propagating pulses: the coupling is enhanced when the pulses interfere constructively in the center $(\ensuremath{\phi}=0)$, while it is nearly suppressed when they are out of phase $(\ensuremath{\phi}=\ensuremath{\pi})$.
The phase-dependent feature of few-cycle pulsed laser propagation in a resonant two-level atom medium is demonstrated by solving the full Maxwell-Bloch equations. Even in the perturbative region, the propagating carrier field and the corresponding spectra of the few-cycle pulsed laser are sensitive to the initial phase due to self-phase modulation. For the larger pulse area, the fact that the carrier-wave reshaping comes from the carrier-wave Rabi flopping is also responsible for this sensitivity, and the phase-dependent feature is more evident.