Organic nonlinear optical (NLO) materials provide an alternative to conventional inorganic crystals with the potential to provide high nonlinear susceptibilities in an economical fabrication process. NLO materials based on ionic self-assembled multilayers (ISAM) films are particularly promising because of the ease of tailoring noncentrosymmetric structures and the long-term stability [1,2]. These films are made by alternately immersing a substrate in two solutions, containing a polycation and a polyanion, respectively. If the substrate initially carries negative surface charges, dipping in the polycation solution will result in a nanoscale polymer layer self- assembled on the substrate, yielding a positively charged substrate. Subsequent dipping in the polyanion solution results in a second layer of the polyanion formed on top of the first layer. The process can be repeated as many times as desired, building up films to arbitrary thickness with nanoscale precision. ISAM films may have substantial χ(2) values, comparable to that of lithium niobate[2]. Here, we demonstrate a new approach to enhance the second-order NLO susceptibility by several orders of magnitude by creating hybrid structures from ISAM films and noble metal nanoparticles [3].
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