We demonstrate the possibility of extension of the open aperture Z-scan technique to measurement of nonlinear refractive indices for self-phase modulation and two-color cross-phase modulation
of optical materials by measurement of power-weighted time-averaged propagation factor [M<sup>2</sup>(t)] of the beam after the sample.
The influence of the temporal shape of the pulse is investigated for two cases: when the pulse peak intensity at the beam waist is known, or when the total energy of the pulse and the duration of the correlation function are known only. Numerical calculations show that the determined values of refraction indices might vary noticeably if the proper pulse shape is not taken into account.
New results of the numerical and experimental investigation of compact solid-state lasers with pulse compression by backward stimulated scattering and multipass laser amplifiers are presented. New models of the master oscillator with the combined passively and actively Q-switched Nd:YAG produce single-mode pulses whose energies are approximately 6 mJ, duration < 2 ns and timing jitter approximately 5 ns. Investigations of Cr<SUP>4+</SUP>:YAG crystal bleaching by 150 ps and 2.3 ns long pulses with the Gaussian intensity distribution permitted to obtain more reliable values for ground and excited state absorption cross sections. Application of the active Q-switching with negative feedback enabled to achieve synchronized single-mode pulses with the duration of < 2 ns and the energy of approximately 7 mJ with energy deviations of +/- 1.5% and timing jitter of < 0.5 ns. It is shown that the SBS-compressor filled with heavy fluorocarbons and pumped by amplified (approximately 40 mJ) symmetrical short (approximately 2 ns) pulses can produce the Stokes pulses with 25 mJ energy and the duration as short as 90 ps. A modified Nd:YAG laser with a hybridly Q-switched master oscillator and heavy freon as a Brillouin medium and a multipass Nd:YAG amplifier can generate pulses with the duration of approximately 100 ps and the energy of > 0.6 J at repetition rates of approximately 10 Hz with pulse jitter approximately 1 ns.