We report the experimental investigation of the thermo-optical effects that limit the brightness of radiation in the diode-end-pumped lasers with Ng- and Np-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.

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