Polymer composites doped with nonlinear optical species have been shown to have large nonlinear optical susceptibilities, and are of prime interest in the study of photorefraction.\u00a0 These composites consist in part of a moiety responsible for a linear electrooptic effect, essential for photorefraction and directly related to its strength.\u00a0 This role is filled by chromophores (the nonlinear optical species), each acting as a dipole, in the polymer composites to be studied.\u00a0 In order to observe photorefraction in polymers an external electric field must be applied to align these chromophores, thereby creating a noncentrosymmetric media and making second order effects such as the electrooptic effect possible.\u00a0 The dynamics of how the chromophores align with the electric field and with the photogenerated space charge field associated with the photorefractive effect are of great interest in the understanding of the photorefractive response and dynamics.<\/span><\/p>\n \u00a0\u00a0\u00a0\u00a0\u00a0 Previous work focused on electric field-induced second harmonic generation (EFISH) and ultra-fast laser pulses for the purpose of understanding this orientational dynamic has also resulted in the observation of several surprising phenomena.\u00a0 Among these are an unexpected initial rise and fall in second harmonic generation (SHG) in several composites and an increase in SHG in polymers doped with C60<\/sub> (buckyballs) when exposed to He-Ne light.\u00a0 These processes and their relation to chromophore orientation will be studied and characterized both experimentally and theoretically.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":" Andrew Stickrath with Ken SingerOrientational Mobility of Chromophores in Photorefractive Polymer Composites<\/p>\n Polymer composites doped with nonlinear optical species have been shown to have large nonlinear optical susceptibilities, and are of prime interest in the study of photorefraction.\u00a0 These composites consist in part of a moiety responsible for a linear electrooptic effect, essential for photorefraction and directly related to its strength.\u00a0 This role is filled by chromophores (the nonlinear optical species), each acting as a dipole, in the polymer composites to be studied.\u00a0 In order to observe photorefraction in polymers an external electric field must be applied to align these chromophores,<\/p>\n