"In this thesis, CW-pumped Nd:YVO4 lasers passively Q-switched with LiF:F2- and YAG:Cr4+ saturable absorbers are modeled and comparatively analyzed. The model takes into account the geometric factor representing the distributions of the orientations of the F2- color centers and Cr4+ ions relatively to the corresponding crystalline hosts on the output parameters of the lasers. It is shown that the LiF:F2- Q-switching has evident advantages over the YAG:Cr4+ one, in the senses of a much more expanded range of pump powers where the giant-pulse regime is supported in the laser and, as the consequence, of potentially higher average output peak pulse powers accessible. Additionally, passive Q-switching (PQS) of a diode-side-pumped Nd:YVO4 laser using a LiF:F2- crystal as a saturable absorber is reported. Applying the grazing-incidence geometry to the cavity, we obtained trains of giant pulses of minimal duration of ~10 ns and peak power of hundreds watts. The laser efficiency and beam quality in the PQS regime are shown to strongly depend on the cavity arrangement and output coupler reflectivity. In particular, maximum of average output of 18.5 W at high-quality (TEM00 mode) PQS operation is obtained at pump power of 38 W at the asymmetrical cavity coupled by a mirror with reflectivity 30%. A theorical modeling of the PQS Nd: YVO4 / LiF:F2- laser is performed as well; its results are demonstrated to be in agreement with experimental data."