NONLINEAR ABSORPTION OF CR4-YAG STUDIED WITH LASERS OF DIFFERENT PULSEWIDTHS()

A saturable absorber Cr4+:YAG, used for a passive Q switching of Nd: Y AG laser was studied in order to understand the physical mechanism of nonlinear absorption (photobleaching). An optical bleaching experiment was carried out using the two pulsed lasers with duration of pico- an d nanoseconds at 1.064 mu m wavelength. Experimental results were comp ared with numerical analysis of theoretical rate equations with all re levant energy levels. The inclusion of intersystem crossing between si nglet- and triplet- excited states with reasonable rate of transition k(isc) was necessary to explain the difference in the saturation behav iors for nanosecond and picosecond laser pulses. (C) 1998 American Ins titute of Physics. [S0003-6951(98)02448-6].