The orientation relaxation upon photo-induced isomerization of azo-dyes was studied. All-optical poling (AOP) and photo-induced birefringence, which are based on the mechanism of angular selective photo-isomerization, were employed to manipulate the angular distribution of azo-dyes (Disperse-red 1) doped in three different amorphous polymers: (poly(methyl methacrylate) PMMA, poly(carbonate) PC and poly(sulfone) PSU), with different glass transition temperature (T<sub>g</sub>). In the case of AOP, quasi-permanent macroscopic second-order nonlinear optical susceptibility χ<sup>(2)</sup> was inscribed in the dye-doped centro-symmetric polymer systems, while in the case of photo-induced birefringence, quasi-permanent birefringence Δn was inscribed in the dye-doped isotropic polymer systems. Relaxation of χ<sup>(2)</sup> and Δn were monitored upon different duration of AOP and photo-induced birefringence preparation. Experimental results show that azo-dye orientation relaxation follows the duration of the photo-nduced isomerization process: the longer the photo-induced isomerization process, the slower the relaxation of the inscribed χ<sup>(2)</sup> and Δn. In addition, retardation of the orientation relaxation does not follow a simple relation with hardness (T<sub>g</sub>) of the polymer host. Causes of the orientation relaxation retardation are discussed.
In this work we report on the preliminary results of compatibility, fabrication and characterization of two planar polymeric multilayer structures for electro-optic applications. The structures are composed by three polymeric layers grown on glass substrate. Buffer and cladding layers were synthesized using polymethylmethacrylate (PMMA). The guiding layers were composed by Polysulfone (PSU) and by a mixture of PMMA and polycarbonate (PC) both doped with Disperse Red 1 (DR1) molecules as nonlinear active units. Linear and nonlinear optical characterization of the structures by refractive index, absorption, optical losses, Second Harmonic Generation (SHG) and time stability measurements have been carried out.
Guest-host polymer system with potential use in electro-optic devices is discussed. The polymer host is a polyimide and the guest chromophore is Disperse Red 19 (DR 19). Decay times of poled order after corona poling procedure have been derived from the behaviour at elevated temperatures below glass transition temperature T<sub>g</sub> using Arrhenius plots. An extrapolated lifetime greater than 30 years at room temperature has been obtained.