Abstract
By using the exact analytical solution and exploring the effect of ultra-short strong pulses in the presence of an external classical field for a two-level atom, we discuss the influence of the phase jump on the behavior of the atomic inversion, coherence and squeezing entropy during the time evolution of various pulse shapes. We show the optimal conditions to attain the phenomenon of coherence trapping. Moreover, we identify the range of physical parameters required for squeezing and its enhancement. The few-cycle pulses present new interesting features for controlling the physical quantities and are a good candidate to perform quantum optics tasks.