11 September 2013 Observation of switching between SA and RSA in silver/goldpolyaniline nanocomposite films
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In the present work, attempts have been made to embed Silver (Ag) /Gold (Au) - nanoparticles into polyaniline (PANI) matrix using an easy wet chemical route. It is expected that the resulting nanocomposite will show the interesting third order nonlinear optical characteristics of Ag/Au-nanoparicles modified by the advantageous properties of the conducting polymer PANI. Structural characterisation of Ag/Au-PANI nanocomposite samples was done using X-ray diffraction and Raman studies. UV-visible absorption spectra show the presence of surface plasmon resonance (SPR) peaks centred at 410 nm and 520 nm for Ag-PANI and Au-PANI nanocomposite films respectively, which is a signature of nano dimensionality of the composite samples. Third order nonlinear behaviour of the nanocomposite films was analysed using Z Scan technique employing the second harmonic output (532 nm) of a Q-switched Nd:YAG laser (Minilite, Continuum). It is seen that Ag/Au-PANI nanocomposite film samples show simultaneous presence of saturable absorption (SA) and reversible saturable absorptions (RSA) behaviour at 50 μJ laser excitation. This switching between SA and RSA has been reported in many metal nanocomposite systems. However similar behavior in nanocomposite film samples has not been pursued much. The highlight of the present work is the observation of the switching between SA and RSA in Ag/Au polyaniline nanocomposite films. The switching behavior can be ascribed to the interplay between ground state plasmon band bleaching and excited state absorption. Two photon assisted absorption has been identified as the prime factor contributing towards the observed RSA in these nanocomposite films.
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P. B. Anand, P. B. Anand, S. Jayalekshmi, S. Jayalekshmi, "Observation of switching between SA and RSA in silver/goldpolyaniline nanocomposite films", Proc. SPIE 8809, Plasmonics: Metallic Nanostructures and Their Optical Properties XI, 88092B (11 September 2013); doi: 10.1117/12.2027206; https://doi.org/10.1117/12.2027206

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