Model of a passively Q-switched laser accounting nonlinear absorption anisotropy in a passive switch

Interest to the passive Q-switching mode in lasers does not fade on decades. Manufacturing in the last time of new passive Q-switches (PS) of crystalline type allows one to realize this regime for lasers of the broad spectral range. This, in turn, demands to perfect the model describing this mode of oscillation. In particular, general formulas for output energy and giant pulse duration are recently generalized for the case of excited state (ES) absorption in PS with phototropic centers (PC). The aim of the present paper is further developing of this model, i.e. finding general formulas for output energy and duration of giant pulse, taking into account: (i) PC orientations in crystalline PS (is done at first) and (ii) the ratio of generation spot sizes in PS and active medium (AM). On the one hand, despite to be considered in a sample of classic works, (ii) is used in incorrect form in others. On the other hand (ii) is not reflected in general expressions. Our paper is aimed to fill these gaps. Here, we present the theoretical analysis of the generalized model; its verification by the experiment with a Nd:YAG laser passively Q-switched with PS based on an LiF:F₂ ^- or an Cr⁴⁺:YAG crystal; and the main conclusions of the work