High-power cw and quasi-cw lasing at the fundamental and second harmonic frequencies is obtained from Nd:KGd(WO 4 ) 2 lasers based on N p -and N g -cut crystals pumped longitudinally by a diode laser at 879 nm. Because of different crystal lengths, the limiting pump power beyond which the crystals undergo thermomechanical damage is 26.8 W for the N p -cut and 17.3 W for the N g -cut. At these pump powers the cw outputs at λ = 1067.2 nm are 9.4 and 5.4 W, respectively, and the N g -cut crystal output is TEM 00 at the fundamental frequency. With quasicontinuous pumping at a 10% duty cycle the instantaneous laser power reaches ~11 W for both cuts with a periodic duration of 10-20 ms. The differential lasing effi ciency relative to the absorbed pump power is 66.4% for cw lasing and 77.4% for quasi-cw operation. With intracavity frequency doubling using a KTP crystal, better results were obtained with the N g -cut crystal because of its simpler thermal lensing. The maximum second harmonic power was ~1.1 W for cw operation and ~2.6 W for quasi-cw operation with a diode laser power of 27.3 W.Introduction. Of the solid-state matrices doped with trivalent rare-earth ions used as laser media and phosphors, crystalline potassium-gadolinium tungstate KGd(WO 4 ) 2 (referred to as KGW in the following) is exceptional. Crystalline KGW can be doped with isolated ions of Nd 3+ , Yb 3+ , Er 3+ , Ho 3+ , Tm 3+ , Pr 3+ , Dy 3+ , Eu 3+ [1][2][3][4][5][6][7] or their combinations, such as Er and Yb [8], Ho and Tm [9], Yb, Ho, Er, and Tm [10], etc. Since the ionic radius of the replaced Gd 3+ ion is close to the ionic radii of the other lanthanoids, the concentration of impurity centers in a KGW crystal can be quite high without causing signifi cant bulk deformations of the crystal lattice. For example, in the well known and easily available laser medium Nd:KGW the concentration of neodymium ion ranges from 3-10 at.%. In addition, the KGW matrix is active with respect to induced combination (Raman) scattering. Because of this, Nd:KGW lasers with fl ashlamp and diode pumping operate both at the fundamental wavelengths of the 4 F 3/2 -4 I 11/2 and 4 F 3/2 -4 I 13/2 transitions (1067.2 [11-13] and 1351 nm [14][15][16]) and at the wavelengths of the Stokes components owing to Raman self-conversion of the fundamental frequency (1180 [17], 1500 [18], and 1538 nm [19]). The combination of Raman conversion with the second harmonic (SH) generation or combination frequency effect makes it possible to obtain coherent light in the yellow region of the spectrum at wavelengths λ = 560 [20] and 590 nm [21] from Nd:KGW lasers.Nd:KGW lasers with frequency doubling of the fundamental at λ = 1.0672 μm have been discussed in the literature [22]. The distinctive feature of these lasers (λ l = 533.6 nm) is that they are suitable for optical pumping of Eu:KReW (where Re = Gd, Y, Lu) active media [7,23,24]. Pumping is in the 7 F 1 -5 D 1 absorption band of the europium ion. With pumping by a pulsed (Q-switched) frequency doubled Nd:KGW laser, for the fi rst...

Herein, on the basis of expressions for the refractive indices of isonormal waves, the possibility of performing collinear phase matching for optical parametric generation in arbitrary directions of a biaxial KTA crystal under pumping by radiation of a YAG:Nd laser is analyzed. The tuning curves that determine the tuning range of the signal and idler for type-I and II-type phase-matching and arbitrary angles θ and φ in cases where the tuning is carried out along the angle θ at a fixed angle φ and vice versa are calculated. The effective nonlinear coefficient is determined. It is shown that their maximum value is achieved аt a polar angle θ = 90° and type-II phase-matching. For the case of generation of eye-safe radiation the spectral and angular phase matching widths were estimated, as well as gain widths of KTA-OPO under monochromatic pumping.