Circularly polarized molecular high-order harmonic generation in H~(2+) with intense laser pulses and static fields

摘要

Molecular high-order harmonic generation (MHOHG) by a combined intense circularly polarized laser pulse and static electric field has been studied from the appropriate time-dependent Schrodinger equation (TDSE) for the H2+ molecular ion. It is found that for a particular static field strength derived from a classical model, efficient MHOHG spectra are obtained with maximum energy I_p + 9.05U_p, where I_p is the ionization potential and U_p = E_0~2/4m_eω_0~2 is the ponderomotive energy at amplitude E_0 and frequency ω_0 of the circularly polarized laser pulse. The static field controls recollision of the electron with parent ions and is confirmed by numerical solutions of the H_2~+ TDSE at equilibrium. To produce circularly polarized MHOHG spectra, a combination of an elliptically polarized pulse and a static electric field is found to be most efficient. A time-frequency analysis obtained via Gabor transforms is employed to identify electron recollision times responsible for the generation of these high-order harmonics. It is found that only single recollision trajectories contribute to the circularly polarized harmonics, thus generating new sources for high-frequency circularly polarized attosecond pulses.