Optical limiting properties of a zinc porphyrin polymer and its dimer and monomer model compounds

We report on the strong decrease in laser light transmission with increasing excitation intensity observed in thin films of a zinc porphyrin polymer and its dimer and monomer model compounds. Nonlinear transmission measurements performed at 532 nm using 500 ps laser pulses show decreases of 40%, 60% and 65% at input fluences of 0.01 J/cm² for the monomer, dimer and polymer thin films, respectively. Its application as an optical limiting device for the protection of the eyes and optical sensors from high-fluence laser pulses is assessed. Additional pump-probe measurements performed at 595 nm using 0.8 ps excitation allow us to discuss the strong response in terms of a six-level model of the electronic structure.