COLLIMATION AND FOCUSING OF PARAXIAL WAVE PACKET OBTAINED BY DIFFRACTION IN THE FAR AREA OF INITIAL SINGLE-CYCLE WAVE
It is shown that during the collimation of paraxial wave packet generated by diffraction in the far area of initial single-cycle wave a "W-shaped" 1.5 cycle spatiotemporal structure is formed, and its duration is proportional to the distance from the beam axis, and its central part is moving faster than the peripheral. With the increase of propagated distance by a collimated radiation from the collimating to focusing mirror the wave packet in the focus changes from 1.5 cycle wave to single-cycle and again backwards, the maximum of its spectrum is shifted first to the high frequencies at the beam axis and then back to the low frequencies. Single-cycle wave at the mirror focus is identical to the original one for collimating and focusing mirrors with equal focal lengths and distance between them is equal to twice focal length.