Pulse polarization evolution and control in the wake of molecular alignment inside a filament

The polarization evolution and control of a femtosecond laser pulse in the wake of molecular alignment inside a laser filament was investigated. A weak probe pulse was delayed with respect to the fieldfree revivals of the pre-excited rotational wave-packets created by an infrared filamenting pulse in nitrogen gas. 30° was set between the pump and probe's initial linear polarization directions in order to control the output probe's polarization ellipse. The detailed physical response of the probe's polarization states was analyzed in the wake of alignment and dephasing of molecular N₂. The probe's polarization was modulated by varying the retarded time between the pump and probe pulses.