Effect of nonlinear light scattering in air on ablation of materials produced by femtosecond laser pulses

Nonlinear light scattering appearing upon air breakdown induced by high-power ultrashort pulses (110 – 5200 fs) from a Ti:Al₂O₃ laser is studied. As a result of forward scattering, the beam profile is severely deformed, which is accompanied by spectral conversion of the incident radiation to a series of shorter-wavelength peaks extending into the visible spectral range. Measurements are made of the thresholds and the scattered radiation energy, which amounts to 75% of the incident energy. The effect of scattering on the material ablation in air is investigated. The obtained data offer an explanation for the experimentally observed paradoxical morphology of the channels ablated by high-power femtosecond pulses.