Features of diffraction and collimation of few-cycle optical beams

The paper reports theoretical spectral and spatial-temporal features of diffraction and collimation of few-cycle optical beams in transparent isotropic linear media. Equation describing asymmetric distribution in temporal structure of electric field in far field region of diffraction, which with increasing distance becomes symmetric is given. It is shown the frequency of maximum spectral density increases with distance from source of radiation along the axis of propagation. The frequency shift is inversely proportional to the initial duration of the wave packet and decreases with increasing of oscillations number.