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second harmonic generation diagnostic of polymers and elecronic matarials.

Abstract : Nonlinear optical response stability of azo-dye (disperse red 1) doped amorphous glassy polymers prepared by spin-coating and azo-dye functionalized polymer prepared by Layer-by-Layer self-assembly process is studied and discussed. Results of second order nonlinear susceptibility relaxation reveal that rotational stability of dopant depends not only on glass transition temperature but also on polymer architecture. Retardation of rotational relaxation of dopant upon All-Optical Poling is discussed. In addition, a ‘restoring torque' model is introduced for understanding intrinsic orientation stability of azo-dye in Layer-by-Layer nonlinear optical polymer.

Second order nonlinear optical properties of a polar inorganic crystal (Zinc Oxide) scaling from milli-meter to nano-meter is studied. Size effect of zinc oxide crystal to its second order nonlinear susceptibility is studied. Second Harmonic Generation (SHG) measurement shows that for nano-scale zinc oxide crystal, surface effect has to be taken into account for its contribution to SHG. Enhancement of SHG in nano-scale zinc oxide is attributed to efficient charge separation at nano-crystal surface. Electric Field Induced Second Harmonic Generation (EFISHG) contributes significantly to SHG of nano-size zinc oxide clusters due to the establishment of strong local external electric field across nano-structure. Quantity of charge accumulation during photo-excitation is also estimated.

Centro-symmetric electronic materials fullerene (C60) and copper phthalocyanine (CuPc) are found to give high second order nonlinear optical response which is not comprehensible under the consideration of the absence of dipole-allowed high second harmonic generation contribution. Inverse proportionality of sample thickness to its second order nonlinear response suggests that quadratic nonlinear optical response of C60 and CuPc do not originate from higher order nonlinear optical mechanisms. We propose that there is a spontaneous charge transfer at the interface of substrate and organic film (C60 or CuPc) which leads to EFISHG effect. Kelvin probe technique for surface potential measurement is discussed for investigating interfacial charge transfer phenomena.
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Submitted on : Wednesday, July 4, 2007 - 3:40:39 AM
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  • HAL Id : tel-00159741, version 1


Siu-Wai Chan. second harmonic generation diagnostic of polymers and elecronic matarials.. Atomic Physics [physics.atom-ph]. Université d'Angers, 2007. English. ⟨tel-00159741⟩



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