Nonlinear optical absorption of zinc-phthalocyanines in polymeric matrix

We realized and investigated films of zinc-phtalocyanines into poly(methylmethacrylate) (PMMA) for optical limiting applications. The ratio by weight of the compound to the host polymer was 0.083% and 0.15%. Linear optical characterization of films, performed by spectrophotometry, show a low degree of molecular aggregation of zinc-phtalocyanines in the polymeric matrix.Two different type of nonlinear optical investigation were performed separately on the obtained films. Measurements of nonlinear transmission were carried out using a ns Nd:Yag laser followed by OPO (532 nm) and a nonlinear response was observed. From the experimental data, the nonlinear absorption coefficient β was retrieved and found to be 29 and 43 cm/GW, respectively. The measurements of β was also performed via the z-scan technique on the same films, using 100 fs pulses at 800 nm. At this wavelength, the nonlinear absorption coefficient was evaluated to be 0.40 and 0.23 cm/GW.