Saturable and Reverse Saturable Absorption in Nanocomposite Films of Naphthol Green B Dye-polymer System.

Naphthol Green B dye-polyvinyl alcohol composite films were fabricated and their nonlinear absorption properties were investigated using the Z-scan technique under excitation with 5ns laser light pulses at 532 nm. The samples displayed a switchover from saturable absorption to reverse saturable absorption with increase in either intensity or concentration. The measured values of β and I_S were found to be of the order of 10^-7 cm/W and 10⁹ W/cm² respectively. The atomic force microscopic analysis of the composite films revealed homogeneous distribution of aggregated nanoclusters marked by a low average surface roughness ≈1.8 nm. [ABSTRACT FROM AUTHOR]