Passive Q-switching of diode pumped Nd: KGd(WO4)(2) lasers by V3+: Y3Al5O12 crystal with anisotropy of nonlinear absorption

Use of a V3+:y(3)Al(5)O(12) crystal as a saturable absorber Q-switch for 1.07 and 1.35 mu m Nd:KGd(WO4)(2) diode pumped lasers shows a considerable dependence of output characteristics on the orientation of the intracavity field polarization vector regarding V3+:y(3)Al(5)O(12) crystallographic axes. Anisotropy of nonlinear absorption of V3+ ions in a Y3Al5O12 single crystal at wavelengths of 1.08 and 1.35 mu m has been experimentally studied. The experimental data are analyzed within the framework of a phenomenological model when the V3+ ions are described as three sets of linear dipoles oriented along the crystallographic axes. Ground-state and excited-state absorption cross sections at 1.08 and 1.35 mu m are evaluated to be sigma(gsa) = 3.4 x 10(-18) cm(2), sigma(esa) = 3.0 x 10(-19) cm(2) and sigma(gsa) = 5.4 x 10(-18) cm(2), sigma esa = 4.8 x 10(-19) cm(2), respectively. Saturation fluence and intensity at 1.08 and 1.35 mu m are estimated as 55 mJ/cm(2) and 1.1 MW/cm(2), respectively. (C) 2007 Optical Society of America.