Critical power for self-focusing in the case of ultrashort laser pulses

We attempt to evaluate the applicability of the concept of the critical power for self-focusing, originally developed for intense quasi-continuous-wave (cw) beams, to the case of ultra-intense and ultrashort laser pulses propagating in air. Our results show that, unlike in the cw case, no particular value of peak pulse power can be viewed as a sharp demarcation line between linear and nonlinear propagation regimes. Our analysis further reveals the important role played by chromatic dispersion in the propagation dynamics of the laser pulse.