Ultrafast pulse interactions with two-level atoms

An iterative predictor-corrector finite-difference time-domain method is used to solve the semiclassical Maxwell-Bloch system numerically without invoking any of the standard approximations such as the rotating-wave approximation. This approach permits a more exact study of self-induced transparency effects in a two-level atom. In addition to recovering the standard results, for instance, for , 2, and 4 pulses, several features in the results appear at the zeros of the driving pulse, where its time derivatives are maximum. Several ultrafast-pulse examples demonstrate that time-derivative- driven nonlinearities have a significant impact on the time evolution of a two-level atom system. Moreover, typical small-signal gain results are also obtained with our Maxwell-Bloch simulator. We illustrate that these time-derivative effects can be used to design an ultrafast, single-cycle pump pulse that completely inverts the two-level atom population. A pump-probe signal set is then used to illustrate gain in the probe signal.