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Optimisation of poling parameters for nonlinear optical polymers from their dipolar orientation and relaxation behaviour

: Gerhard-Multhaupt, R.; Bauer, S.; Ren, V.; Yilmaz, S.; Wirges, W.

Molecular crystals and liquid crystals, science and technology. B, Nonlinear optics 11 (1994), No.1-4, pp.309
ISSN: 1058-7268
International Conference on Organic Nonlinear Optics (ICONO) <1, 1994, Val Thorens>
Journal Article, Conference Paper
Fraunhofer HHI ()
corona; dielectric polarisation; dielectric relaxation; electro optical effects; nonlinear optics; optical polymers; optimisation; polarisability; thermal analysis; thermally stimulated currents; nonlinear optical polymers; dipolar orientation; relaxation behaviour; poling parameter; molecular dipoles; hyperpolarisability; glassy polymer matrix; guest-host system; polymethylmethacrylate; disperse red; disperse red-styrene-maleic-anhydride-based side-chain material; corona-poling experiment; dielectric spectroscopy; thermally stimulated depolarisation; electro-optic thermal analysis; dielectric behavior; havriliak-negami equation; Mastercurve; time-temperature superposition principle; glas transition temperature; relaxation-time distribution; mean relaxation times

Summary form only given, as follows. Nonlinear optical polymers contain molecular dipoles with very large hyperpolarisabilities in a glassy polymer matrix. Two typical examples-a guest-host system of Polymethylmethacrylate (PMMA) and Disperse Red 1(DR1) and a DR1-styrene-maleic-anhydride-based side-chain material kindly provided by SANDOZ Optoelectronics, Huningue, France-were studied with corona-poling experiments, dielectric spectroscopy, thermally stimulated depolarisation (TSD), and electro-optical thermal analysis (EOTA). It was found that the dielectric behaviour of both polymers can be described by the phenomenological Havriliak-Negami equation. The existence of master curves for both materials demonstrated the validity of the time-temperature superposition principle above their respective glass-transition temperatures. Mean relaxation times and calculated relaxation-time distributions for the guest-host and the side-chain polymer permit the selection of optimal poling durations. The guest-host system's relaxation-time distribution is broader and has more short-time components than that of the side-chain polymer. From the results of short-circuit TSD-current measurements, the overall sample polarisation is obtained by integration. The values agree reasonably well with estimates from the poling-current measurements and with the dielectric data. From the temperature dependence of the polarisation, optimal poling temperatures may be derived.