We investigate the effect of laser frequency chirp on the generation of a dense energetic electron sheet. The direct acceleration regime of laser driven dense electron sheet requires high laser intensity to function efficiently. We demonstrate this requirement can be relaxed by applying chirped lasers. The acceleration becomes more efficient while driven by a pulse with a proper linear chirp, leading to a dense energetic electron sheet in nanoscale, and therefore requires lower laser intensity.

The feasibility of population transfer from a populated level via an intermediate state to the target level driven by fewcycle pulses is theoretically discussed. The processes of on-or far-resonance stimulated Raman scattering with sequential or simultaneous ultrashort pulses are investigated respectively. We find that the ultrashort pulses with about two optical cycles can be used to realize the population operation. This suggests that the population transfer can be completed in the femtosecond time scale. At the same time, our simulation shows that the signal of the carrier-envelope-phase-dependent effect can be enlarged due to quantum interference in some conditions. Our theoretic study may promote the research on the coherent control via ultrashort pulses in the related fields.