Field-free molecular orientation by two-color shaped laser pulse together with time-delayed THz laser pulse

摘要

We theoretically investigate field-free molecular orientation by using an off-resonant two-color shaped laser pulse with a slow turn-on and rapid turn-off and a time-delayed THz laser pulse. It is shown that the molecular orientation can be greatly enhanced by applying this scheme compared to the two-color shaped or THz laser pulse alone. We discuss the effects of the rise time and the electric field amplitude of the two-color shaped laser pulse on molecular orientation, and demonstrate that effective molecular orientation can be achieved by a moderate intensity laser pulse with a short rise time. Furthermore, by changing the delay time between the two-color shaped laser pulse and the THz laser pulse and the carrier envelope phase of the THz laser pulse, the molecular orientation can be enhanced or lowered to some degree.