Propagation of ultrashort laser pulses in dry and humid air

Propagation of an ultrashort laser pulse in the atmosphere is considered with allowance for diffraction and dispersion properties of the atmosphere. Results of numerical simulation of the propagation of pulses with a duration from several to tens of femtoseconds in air at a room temperature are presented. A rapid spreading of such pulses under the corrected Gaussian form of the time envelope is shown. The propagation of a pulse with a negative initial chirp in dry and humid air is calculated; the chirp makes it possible to partially compensate dispersion and diffraction effects. The distance at which the pulse duration becomes minimal is derived as a function of air humidity.