Field-free alignment and orientation of linear molecules by two-color trapezoidal laser pulses
The field-free alignment and orientation of the linear molecule by the two-color trapezoidal laser pulses were theoretically investigated. The trapezoidal shape of a laser pulse allows to enhance the maximum alignment degree for the same intensity and duration comparing to the conventional Gaussian laser pulse. The alignment and orientation persist after the pulse for both non-adiabatic and adiabatic regimes. While the maximum (during the pulse) alignment degree quickly saturates and remains almost constant with the pulse duration increase, the dependencies of the maximum (outside the laser pulse) alignment and orientation degrees on the pulse duration show the clear periodic structures in the adiabatic regime. The effect of the non-zero temperature is also shown. Applying additional the monochromatic or two-color prepulse increases the maximum orientation degree, but the application of the two-color prepulse leads to a higher maximum orientation degree than the monochromatic prepulse. The effect of the relative phase variation on the molecular orientation in case of one and two pulses was also discussed.