The results of the formation and amplification of positive chirped 0.1 ns laser pulse at a central wavelength of 470 nm in the laser system THL-100 are presented. It is shown that a front-end allows forming a radiation pulse with a Gaussian intensity profile and the energy up to 7 mJ. At amplification in XeF(C-A) amplifier of the pulse with 2-5 mJ energy a saturated mode is realized and 3.2 J output laser beam energy is reached.
We present the results of studies of energy accumulation during the non-destructive interaction of extremely intense near infrared laser radiation with model wide band gap dielectric crystals of lithium fluoride, when the intensity of pulses is sufficient for effective highly nonlinear absorption of light and for the excitation of the electron subsystem of matter and the energy of pulses is still not sufficient for significant heating, evaporation, laser breakdown or other destruction to occur. We studied the emission of energy in the form of light sum of thermally stimulated luminescence accumulated under conditions of self-focusing and multiple filamentation of femtosecond laser radiation. It was established that it's the F<sub>2</sub> and F<sub>3</sub><sup>+</sup> color centers and supplementary to them centers of interstitial type which accumulate energy under the action of a single femtosecond laser pulses. When irradiated by series of pulses the F<sub>3</sub>, F<sub>3</sub><sup>-</sup> and F<sub>4</sub> centers additionally appear. F<sub>2</sub> centers are the main centers of emission in the process of thermally stimulated luminescence of accumulated energy. The interstitial fluoride ions (I-centers) are the kinetic particles. They split off from the X<sub>3</sub><sup>-</sup> centers in the result of thermal decomposition of latter on the I-centers and molecules X<sub>2</sub><sup>0</sup>. I-centers recombine with F<sub>3</sub><sup>+</sup> centers and form F<sub>2</sub> centers in excited state. The latter produce the characteristic emission spectrum emitted in the form of thermally stimulated luminescence.
The paper presents the results of theoretical and experimental studies of the second harmonic generation process in the Ti:sapphire femtosecond complex, which includes a generator of the femtosecond pulse, stretcher, regenerative amplifier, two multi-pass amplifiers, compressor and second-harmonic generator. This complex provides the 50-fs pulses with energy of 20 mJ and it is used as a master oscillator in THL-100 hybrid laser system, which operates in the visible region at a wavelength of 475 nm. Experiments and calculations for various beam parameters of the fundamental harmonic, such as radiation intensity, spatial profile of the beam and the level of the noise component were performed. It is theoretically shown that in the absence of the noise component in the beam of the fundamental wave a good uniformity of the second harmonic should be observed. When making the amplitude heterogeneities in the first harmonic even greater heterogeneities in the second harmonic are appeared. It is experimentally shown that with increasing of energy beam the inhomogeneity of the second harmonic beam increases.
The influence of the optical inhomogeneities effect of the prism stretcher elements on the spatial, angular and spectral parameters of the transmitted radiation and the degree of change in the phase aberrations of the laser beam during its propagation in the stretcher are studied. It is shown that the prism material does not allow transmitting of a required diameter of 75 mm without linear distortions of the beam. The maximum intensity and beam diameter allowing to amplify the picosecond pulses in XeF(C-A) amplifier are determined.