Effects of laser defocusing on intermediate species during energy deposition

During dual pulse laser energy addition, when plasma is already present in the focal area, the remainder of the laser pulse is partially reflected causing a different spatial distribution of laser intensity profile compared with the Gaussian profile (defocusing). This study reports on the effects of defocusing during laser energy deposition in hydrogen-air mixture. Three temperature plasma model coupled with Navier-Stokes equation and an independent beam propagation solver to quantify intensity of laser during defocusing are used for the two-dimensional numerical simulations. The results show that the effects of defocusing are more pronounced in long lived species like H2O2 than the short-lived species like O, OH.