A method for selecting laser media for generation of short laser pulses using the forced Kerr lens with a soft aperture has been developed. It is based on measurements of the tuning lasing characteristics of a solid-state laser with a plane-spherical resonator and a narrow longitudinal pump beam as compared to the size of the fundamental mode of an empty resonator. A scheme is proposed in which the active element is mounted close to a flat mirror. The technique based on the example of the Nd:YVO$_4$ laser made it possible to assign the found resonator configurations to the corresponding irreducible fractions determining the degeneracy conditions 1/6, 1/4, 1/2, 1/5, 1/3, 3/8, 2/7. The dependence of the threshold power on the length of the resonator is obtained under conditions of continuous pumping and with optical shutter with a duty factor 100 over the resonator stability region and near the semi-focal configuration, as well as the output power near the specified configuration. The measurement of the generation threshold with a longitudinal spatial resolution of 0.05 mm was sufficient to determine the boundaries of the region corresponding to the stable generation of short pulses.
42.55.Px Semiconductor lasers; laser diodes
42.55.Rz Doped-insulator lasers and other solid state lasers
$^1$Bauman Moscow State Technical University\
$^2$Lebedev Physical Institute of the Russian Academy of Sciences
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