Electron dynamic control for the quantum path in the midinfrared regime using a weak near-infrared pulse

We theoretically investigate the electron dynamics of the high-order harmonics in a wave-form-controlled two-color midinfrared pulse synthesized by a 2000-nm driving pulse and a much weaker 800-nm control pulse. It is shown that the acceleration and the ionization steps can be simultaneously modulated in the few-cycle regime, which not only broadens the bandwidth but also enhances the harmonic yields of the generated supercontinuum with the photon energies of hundreds of eV. The most important result is that the electrons with the highest return kinetic energies, which contribute to the supercontinuum generation near the cutoff, can be ionized near the peak of the electric field where the ionization rate reaches maximum. We also extend this electron dynamic control to the multicycle regime, enabling the generation of a supercontinuum with a bandwidth of 60 eV and an intensity comparable to that of the lower-order harmonics.