Coherent control of multiphoton processes in ultrashort and super intense pulsed laser fields

We present an ab initio quantum investigation of the production and control of a single attosecond pulse using few-cycle intense laser pulses as the driving field. The high-harmonic-generation (HHG) power spectrum is calculated by solving accurately and efficiently the time-dependent Schrodinger equation using the time-dependent generalized pseudospectral (TDGPS) method. The time-frequency characteristics of the attosecond pulse are analyzed by means of the wavelet transform of the time-dependent induced dipole moment. It is shown that harmonics in the supercontinuum regime are synchronized. These pulses can be controlled by the adjustment of the carrier envelope phase. Furthermore, the HHG cutoff position can be controlled through the optimization of the few-cycle chirped laser parameters. Classical results provide complementary and consistent information regarding the mechanisms responsible for the production of the attosecond pulse and for the substantial extension of the cutoff region. We extended the evolutionary optimization scheme for the coherent control of attosecond pulses in frequency and time domains. Coherent control of Rydberg atoms via chirped laser pulses in the microwave region is achieved. Hydrogen, lithium, and sodium atoms exposed to chirped laser fields are robustly driven through a sequence adiabatic passages of lower energy quantum states. In addition, we study the coherence properties of HHG process driven by a train of laser pulses. A frequency comb structure is preserved within each of the produced harmonics and their spacing is given by the reciprocal of the pulse separation tau. The spectral width of individual comb fringes depends upon the number of pulses used. Finally, the frequency comb structure persists even in the presence of appreciable ionization. Lastly, we present an ab initio nonpertubative investigation of the study of HHG from Ar atoms and Ar+ ions by means of the self-interaction-free time dependent density functional theory. Comparing the HHG behavior from Ar atoms and Ar+ ions in the super intense laser field, we conclude that the high energy HHG observed in the recent experiment originated exclusively from the ionized Ar atoms. We studied the electronic structure of carbon nanowires by means of higher-order finite difference pseudopotential method.