Vorticity Generation with Defocusing Effect for Dual-Pulse Laser Plasma in Air *

We consider the dual pulse laser energy deposition, when plasma is already present in the focal area after the first pre-ionizing pulse. The subsequent laser pulse is partially reflected due to changes in the refractive index caused by the laser plasma formation, resulting in the deviation of the laser intensity profile from the Gaussian shape, defined as defocusing effect. We used a three-temperature plasma model coupled with Navier-Stokes equations and the beam propagation solver to quantify how the laser intensity changes with defocusing. The effect of defocusing on the vorticity generation and dual-pulse laser plasma dynamics in air is reported.