The Studies Of The Third Order Nonlinear Properties On Novel Cyanine Chromophores And Their Self-aggregated Thin Films

In the last few decades, scientists have shown great interest in the studies of new nonlinear optical (NLO) materials, due to their wide use and attractive application foreground, for instance, in modern laser technology, optical communication, data storage, optical information process, and other fields. It has become an important project to find new NLO materials of high efficiency. Much emphasis has been put on the organic NLO materials because they have many advantages, such as wide response wave band, good flexibility, high optical damage threshold, low cost, and easy combination and modification.More recently, considerable attention has also been focused on cyanine chromophores as promising candidates for the large optical nonlinearities, the wide transparent range and the polarizability of the conjugated Ï€-electron under an external field. However, most of the investigations always focus on the second-order nonlinear optical properties of cyanine chromophores, and few studies about third-order nonlinearities of cyanine chromophores, even their different condensed slates, has been reported, which impedes the further applications of the cyanine chromophores. In this paper, for the sake of the more understanding and application in cyanine chromophores, the third order nonlinearities of two typical samples are investigated not only in monomer but also in different self-aggregations: (1) The high density J-aggregates film of the centrosymmetric cyanine chromophore(HR1300), with the large third-order nonlinear optical property (x³=2.55×10^-12esu), is fabricated on the silica substrate by the spin-coating technique, and the well-designed film structure is investigated by ultraviolet-visible spectra, infrared (IR) spectra, small-angle X-Ray diffraction, ellipsometer and Atomic Force Microscopy (AFM). It is believed that for the centrosymmetric cyanine chromophore, the inter-molecular electrostatic interaction is contributed to the formation of HR1300 J-aggregation, which will induce a size-enhanced response in the third order nonlinearities. Because in monomers the molecules do not...