November 17, 2005
Photorefractive polymer advancements show promise for holography, optics and data storage
Photoconducting polymers doped with nonlinear optical chromophores have emerged as efficient and inexpensive photorefractive (PR) materials. These materials show promise for applications in dynamic volume holography, image formation, optical processing, reversible data storage, correlation, etc.
Recently, PR polymer composites have gained a great amount of attention due to their large PR effect, structural flexibility, and good processability.J. L. Maldonado, G. Ramos-OrtÃz, O. Barbosa-GarcÃa, M. A. Meneses-Nava, M. Olmos-L³pez, D. RodrÃguez, H. Reyes, B. MuÃ±oz and N. Farfán from Centro de Investigaciones en Ã“ptica and Centro de Investigaci³n y de Estudios Avanzados del Instituto Polit©cnico Nacional (IPN) have published a study in AZojomo*, in which they fabricated PR composites functionalized with a boron derivative nonlinear chromophore.
Their work examined the diffraction efficiency, the optical gain coefficient, the phase shift, and the effect on the chromophore orientation at room temperature as a function of poly(9-vinylcarbazole):9-ethylcarbazole (PVK:ECZ) ratio of PR composites based on the dye 2-(p-chlorophenyl)-(3'-nitrobenzo[d])-(4''-methoxybenzo[h])-1,3-dioxa-6-aza-2-boracyclonon-6-ene.
For the photorefractive performance, two different chromophore concentrations were used, in addition, the ratio of PVK:ECZ was varied to see the effect on the room temperature molecular orientation. Holographic experiments in a tilted four and two wave mixing geometry were performed. Acceptable photorefractive properties were observed for a polymer with a glass transition temperature (Tg) of 77°C. Even at this Tg, the response time was less than one second.
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