Influence of TiO 2 on Second Harmonic Generation in Disperse Red -1 doped Organic-Inorganic Hybrid Thin Films
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1015-BB01-07
Influence of TiO2 on Second Harmonic Generation in Disperse Red -1 doped OrganicInorganic Hybrid Thin Films Congji Zha1, Xinshi Luo2, Anna Samoc1, Andrei Rode1, and Barry Luther-Davies1 1 Laser Physics Centre, The Australian National University, ACTON, ACT0200, Canberra, 0200, Australia 2 Molecular & Health Technologies, CSIRO, Clayton, Melbourne, VIC, 3169, Australia ABSTRACT Disperse Red 1 (DR1) doped TiO2-SiO2 inorganic-organic hybrid polymers were prepared by an anhydrous sol-gel process and second harmonic generation (SHG) of the fundamental 1053nm in these polymeric thin films was measured using Maker-fringe method. The nonlinear optical activity of DR1 in the thin films was studied by corona poling at different temperature (from room temperature to 140 oC), and the stability of SHG after switching off corona power was evaluated by analyzing the SHG decay dynamics. Experimental results showed that the stability of the SHG of DR1 significantly increases with the cross-linkage degree of the TiO2SiO2 hybrid polymer network, and that the second harmonic coefficient d33 increases as the DR1 concentration increases. TiO2-doping can promote the polymerization of unsaturated C=C double bonds in the hybrid thin films during in-situ hot poling, enhancing the cross-linkage of the network of the hybrid material, and resulting in a great improvement of the stability of SHG. The excellent stability of second harmonic generation in the hybrid polymer thin films suggests that TiO2-doped inorganic-organic hybrid polymer is promising for chromophore doping for nonlinear optical applications. 1.
INTRODUCTION
Second harmonic generation and other nonlinear processes have been studied extensively since the demonstration of frequency doubling by Franken et al [1]. However, chromophore doping with the simple guest-host method in conventional organic polymers generally shows very fast decay in the nonlinear optical signals after corona poling. In order to find a solution for this limitation, several methods have been proposed, including chemically binding the chromophore molecules onto the polymer as either a side chain or in the main chain [2-3], and the use of the sol-gel process to freeze the oriented chromophore molecules in a threeñ dimensional rigid inorganic network [4-6]. Thermal treatment under moderate temperature (up to 200 oC) can lead to further cross-linking of the sol-gel inorganic matrix, which is useful for reducing the relaxation of chromophore molecules and improving the stability of SHG. Generally there are two methods to incorporate nonlinear optical chromophores into sol-gel glass networks: physically mixing in a guest-host scheme and chemically covalent linking in a sidechain or main chain scheme. The advantages of physical mixing method include low cost equipment invest and the simplicity of the process with easy manipulation, but the limited solubility of organic chromophores in the inorganic sol-gel glass network is always a drawback. For the chemical covalent linking method, chromophore molec
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