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The main regularities of induced change of light polarization in the field of powerful ultrashort pulses in the resonant gaseous medium are investigated. Frequency-tunable ultrashort pulses allow to observe the polarization plane rotation at large values of detuning, in the different schemes of single-photon and two-photon interaction. On the other hand, the high intensity of these pulses allows to investigate the nonresonant interaction in the crystalline and solid transparent media. Our experiments carried out permit to propose the polarization technique for forming the given parameters pulses or train of pulses. In the observing medium placed between crossed polarizers, at counter propagation, powerful pump and linearly polarized probe pulses interact, because of which the probe pulse polarization changes. The polarization rotation angle as a time function is determined by the intensity of ultrashort pulse, the parameters of medium and frequencies of interacting waves. At the definite choice of the experimental conditions, registering a probe wave after a crossed polarizer we can obtain the pulse which duration is determined by the length of medium, where interaction occurs. Using a nonresonant transparent media we have the possibility of forming the pulses of given duration tunable in a wide spectral region.

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We propose an all-optic Fourier transformer which completely reproduces the field of input radiation by Fourier image of output. The latter will allow to register the temporal envelope of radiation by means of common spectrometric measurement. This performance is similar to the task of classic spectroscopy where instead of amplitude and phase registration of radiation complex field, the temporal and spectral distributions of intensity are measured by oscilloscope and spectrometer. Moreover, the proposed optical Fourier transformer solves the problem of direct phase measurements of ultrashort pulses, as well this problem is reduced to simplest one dimensional registration technique of beams spatial profile of phase.

For the most part, experiments on harmonic generation in rare gases and in laserproduced plasma use multiple pulses illumination from high-power nano-and picosecond lasers, which allows high-order harmonics to be observed in a substantially nonperturbative regime.