Nonlinear Scattering and Absorption Effects in Size-Selected Diphenylpolyynes

The nonlinear optical properties of monodispersed diphenylpolyynes with different chain length were studied by using a nanosecond pulsed laser excitation. A strong optical limiting response was detected at laser fluences above 0.35 J/cm2. The nature of the nonlinear effect as a function of the number of carbon atoms in the linear chain was investigated by the Z-scan technique, determining the molecular second-order hyperpolarizability γ. An interesting coupling was found between the decrease of scattering phenomena and the alignment of longer carbon chains in the focus region. The effect of an external highly intense electric field, combined with a detailed density functional theory (DFT) investigation, has been invoked to explain molecular arrangement, polarizability, isomery, and scattering of diphenylpolyynes. The interesting findings derived from our investigations demonstrate that phenyl-end-capped polyynes could be very interesting for various optoelectronic applications.