Abstract
We have investigated the spectral dispersion of real and imaginary parts of third-order nonlinear optical susceptibility of silver nanospherical particles in the aqueous solution using Z-scan and antiresonant ring interferometric nonlinear spectroscopic (ARINS) techniques by femtosecond pulses from the modelocked Ti:Sapphire laser over the spectral range of 720–820nm. The observed characteristic of imaginary part shows a peak at ∼766nm which coincides with the peak of spectral dispersion of real part induced thermally. The observed peak in the dispersion of nonlinear absorption coefficient at ∼766nm is attributed to the two-photon absorption. This two-photon resonance peak is attributed to l=2 plasmon (quadrupolar mode) arising from the phase retardation effects in the spherical nanoparticles present in our polydispersed sample with their diameters (80±20nm) beyond the quasi-static limit.
Published Version
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