Optical emission spectra of the plasma produced by 1.06 mum Nd:YAG laser irradiation of a potassium titanium phosphate (KTP) crystal in vacuum and in air were recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma in vacuum were determined with the Boltzmann plot method using five Ti(II) emission lines and the Stark-broadened linewidths of neutral K atoms, respectively. The dependence of the electron densities and temperatures on distance from the target surface and on laser irradiance were manifested. In order to see the effect of backing gas, we also performed laser ablation of a KTP crystal in air and compared the results with that of the ablation in vacuum. Gas dynamical parameters of the laser-induced KTP evaporation wave were simulated using a hydrocode developed in our group based on the self-similar solutions of the gas dynamical equations. Moreover, the velocity of the evaporating wave and the vapor pressure were calculated under different laser power densities. (C) 2002 Elsevier Science B.V. All rights reserved.