[en] We report the results of theoretical studies and numerical simulations of optical high-power pulse compression systems based on the spectral broadening in a Kerr nonlinear medium with subsequent pulse compression in a dispersive delay line. It is shown that the effective spectral broadening requires suppressing a smallscale instability arising due to self-focusing, which is possible in quasi-periodic systems consisting of a nonlinear medium and optical relay telescopes transmitting images of the laser beam through the system. The numerical calculations have shown the possibility of broadening the spectrum, followed by 15-fold pulse compression until the instability is excited. (control of laser radiation parameters)

[en] End-diode-pumped lasers based on one and two Yb : KYW crystals operating in cw and Q-switched regimes, as well as in the regime of mode-locking, are studied. The single-crystal laser generated stable ultrashort (shorter than 100 fs) laser pulses at wavelengths of 1035 and 1043 nm with an average power exceeding 1 W. The average output power of the two-crystal laser exceeded 18 W in the cw regime and 16 W in the Q-switched regime with a slope efficiency exceeding 30%.

No abstract available

[en] The interaction of 1.5 ps FWHM laser pulses with solid targets at intensity 10¹⁵-10¹⁷ W/cm² and contrast ratio 10⁶ is studied. Red shift of a 'mirror' reflected fundamental wave and its second harmonic depending on the incident laser pulse energy and angle of incidence are observed. They are associated with Doppler shift corresponding to inward movement of the critical density surface from laser pondermotive pressure. Back scattered light has nonlinear dependence from laser intensity connected with SBS and changing of plasma surface

[en] We present a dual-crystal Yb:KGW laser that is able to operate as a Q-switched oscillator with output power up to 24 W and pulse length of 20 ns, or as a regenerative amplifier with output power up to 21 W and pulse duration below 200 fs after compression of chirped pulses. Both lasers have excellent beam quality with beam parameter M² < 1.2. We discuss some aspects of the design and performance optimization of dual-crystal Yb:KGW laser systems. (letter)

[en] Diode-pump absorption is experimentally studied in a high-power Yb:KGd(WO_4)_2 (Yb:KGW) laser in the presence and absence of lasing. The maximum absorption efficiency in the cw regime exceeds 77% which is by a factor of 1.4 greater than the maximum absorption efficiency in the absence of lasing. The powers of thermo-optical lenses induced in laser crystals during lasing are measured. A strong dependence of the lens power and aberrations on the orientation of laser crystals relative to the propagation direction and polarisation is confirmed. (lasers)

[en] A simple and reliable method for the measurement of the contrast of ultrashort pulses was implemented. It is based on the application of the principles of chirped-pulse spectral interferometry. The method is linear in terms of the field of the investigated radiation and is based on the measurement with interferometric precision of the spectrum of an amplified chirped pulse before it passes through a temporal compressor. It is shown that, when a recording system with a dynamic range of 10² is used, measurements of the contrast up to 10⁵ are possible. The possibility of applying the method for the on-line monitoring of the parameters of the radiation of solid-state laser sources of ultrashort optical pulses is demonstrated. This is done by taking as an example the optimisation of the front end of a neodymium glass picosecond laser system generating ∼1 ps pulses at its output. (control of laser radiation parameters)

[en] The methods for improving the radiation resistance and strength of metallised diffraction gratings for laser pulse compression systems are considered. It is shown that the modification of the method for applying gold on the holographic grating surface provides a substantial increase in the grating damage threshold. It is also shown that the use of additional dielectric coatings allows a further doubling of the damage threshold for nanosecond laser pulses. (laser applications and other topics in quantum electronics)

[en] We report the experimental investigation of the thermo-optical effects that limit the brightness of radiation in the diode-end-pumped lasers with N_g- and N_p-cut Yb:KGW anisotropic crystals. It is shown that the geometry of laser crystals and their relative positioning in relation to the directions of radiation propagation and polarization vector influence essentially the laser output power and beam quality at high pump power. By optimizing the crystal configuration we obtained the output power of 22 W in Q-switched mode and that of 17 W at regenerative amplification of chirped pulses with a beam quality of M² < 1.1. (paper)

[en] We have studied self-action effects (self-focusing and self-phase modulation) and stimulated Raman scattering in an Yb : KGW chirped-pulse amplification laser system. The results demonstrate that self-focusing in combination with thermal lensing may significantly limit the chirped pulse energy in this system (down to 200 μJ) even at a relatively long pulse duration (50 ps). Nonlinear lenses in the laser crystals in combination with thermal lenses bring the regenerative amplifier cavity in the laser system to the instability zone and limit the average output power at pulse repetition rates under 50 kHz. Self-phase modulation, a manifestation of self-action, may significantly distort a recompressed femtosecond pulse at energies near the self-focusing threshold. Stimulated Raman scattering in such a laser has a weaker effect on output parameters than do self-focusing and thermal lensing, and Raman spectra are only observed in the case of pulse energy instability. (nonlinear optical phenomena)