2 October 1997 Spontaneous self-alignment and structural changes of unpoled hemicyanine dopant in silica film
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Hemicyanine doped silica film was fabricated by sol-gel technique. Time evolution of structural changes in hemicyanine and their influence on the second order optical nonlinearity were investigated through UV-Vis absorption and the second harmonic generation measurements. Three factors were found to have dominant influence on the self alignment and optical nonlinearity of the film. Self alignment was believed to complete right after the evaporation of the solvent. Conversion of protonated hemicyanine to monomeric hemicyanine occurred within 4 hours after film deposition. During this period of time the SHG signal continued to rise and finally reached the maximum. The growth of optical nonlinearity was mainly due to deprotonation of hemicyanine molecules. Optical nonlinearity of the film can also be increased by reducing the amount of hemicyanine aggregates in the film. Blue shift of the absorption peaks for aggregate was found during the drying of the film, it was attributed to resulted from enhanced molecular interaction.
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Lei Xu, Liying Liu, Jing Yu, Wencheng Wang, Fuming Li, Zhi-Ming Zhang, "Spontaneous self-alignment and structural changes of unpoled hemicyanine dopant in silica film", Proc. SPIE 3136, Sol-Gel Optics IV, (2 October 1997); doi: 10.1117/12.279152; https://doi.org/10.1117/12.279152

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