Behavioral study of high-order harmonics and attosecond pulse generation via bichromatic driving laser fields

High-order harmonics intensity and subsequently attosecond pulses which are generated after the interaction of some two color femtosecond pulses with helium ions are studied in this paper. Cutoff frequency in the high-order harmonics' intensity spectrum, maximum ionization probability, attosecond pulse intensity and duration in this research are investigated versus the frequency spacing of the two color driving pulse elements (delta omega). It is seen that the cutoff frequency decays exponentially by delta omega, whereas generation of the most powerful and shortest attosecond pulses as well as the maximum ionization probability occurs around the value of delta omega = 0 (Le., for the single color pulses). However, the longest attosecond pulses are generated for the case of delta omega = 0.8 omega(0) (in which omega(0) is the frequency of the fundamental pulse). Finally, the most isolated attosecond pulses are generated for the case in which delta omega = 1.25 omega(0).