Molecular engineering of organic materials for nonlinear absorption in thevisible range: the excited states of tetraphenyl-diamine derivatives

We report on nonlinear absorption measurements of tetraphenyl-diamine dyes developed for use as transparent materials for optical limiting application s in the visible range. All the excited state properties which are relevant to the process are investigated experimentally using three different and c omplementary nonlinear spectroscopy tools. Through a modification of the su bstitution of the peripheral benzene rings of the original dye, we could si gnificantly improve its optical limiting activity, especially in the red re gion where it had a rather poor efficiency.