Experimental study of nonlinear absorption in polymethine dye solutions by the z-scan method

The nonlinear absorption coefficients β and the ratios k of absorption cross sections in the ground and excited states are measured by the open-aperture z-scan method for three polymethine dyes excited by nanosecond 532-nm second-harmonic pulses of a Nd:YAG laser. The values of k measured for the 789, 842, and 823 dyes are 10, 11, and 11, respectively, and correlate with the limiting properties of these dyes.