Third-order nonlinear response of Ag/methyl orange composite thin films

The large third-order nonlinearities of metal nanocluster doped oxide matrix composite films have been investigated widely, but there is very little literature reporting third-order nonlinearity of metal nanoparticle doped azobenzene molecule thin films induced by picosecond laser pulses. This paper has investigated the third-order nonlinearity of colloidal Ag and methyl orange composite films using the Z-scan technique with 38 ps pulses at 532 nm apart from the surface plasma resonance frequency of composite film. Large and negative third-order nonlinearity was observed. The mechanism responsible for the process of nonlinear refraction was discussed in terms of the enhancement of the local field effect, which was confirmed by using the SERS technique. At the end, the figures of merit were evaluated and the results showed that this material would be valuable in the application of all-optical devices.