Field-free molecular alignment by shaping femtosecond laser pulse with cubic phase modulation

We propose a scheme to enhance the field-free molecular alignment by shaping the femtosecond laser pulse with cubic phase modulation. We show that the molecular alignment can be obtained adiabatically during the shaped pulse and can be revived at the full rotational periods with the same degree as that at the peak of the shaped pulse. The behavior of the molecular alignment by the shaped pulse is the same as that by the slow turn-on and rapid turn-off laser pulse. Furthermore, we show that the shaped pulse with cubic phase modulation has a slight advantage in enhancing the field-free molecular alignment by comparing it with the slow turn-on and rapid turn-off laser pulse under the same laser intensity.