Nonlinear absorption of a carbocyanine dye 1,1′,3,3,3′,3′-hexamethylindotricarbocyanine iodide using a z-scan technique

Experimental and theoretical data are presented for the nonlinear absorption of the organic laser dye 1,1′,3,3,3′,3′-hexamethylindotricarbocyanine iodide (HITCI) using a z-scan technique. Experimental data show an induced absorption above laser fluences of 10 mJ/cm2 and a saturation of the nonlinear absorption above fluences of 0.5 J/cm2. A self-consistent theoretical analysis, based on rate equations, is used to predict accurately the results of z scans taken at different pulse energies. Photophysical parameters, including the excited state lifetimes and absorption cross sections are derived for HITCI.