Imaging of Silicon Naphthalocyanine in Toluene

Pulsed-laser shadowgraphs and images of scattered light are combined with limiting and scattering data to build a model of the response of silicon napthalocyanine (SiNc) at concentrations on the order of 10-3 M in toluene to 12-16 ns 532 nm laser pulses over an energy range from 10 nJ to 2 mJ. The inherent spherical aberration induced by the sample has a profound effect on the response. The scattering is extremely intense above pulse energies of 100 µJ. The data indicates the response at pulse energies below 300 mJ is due to reverse saturable absorption. Full absorbance is not observed until the agglomerates vaporize. At fluences approaching 1 J/cm2 a plasma begins to form and the liquid near the window starts to boil. Intense scatter from the boiling liquid combined with plasma absorption produces hard clamping.