Chromophores applications, photorefractivity

Fig.24a-e. Examples of bifunctional chromophores for photorefractive applications a N-2-butyl-2,6-dimethyl-4H-pyridone-4-ylidenecyanomethylacetate (2BNCM) b 1,3-dimethyll-2,2lctramethylene-5- nit roben zirnidazoli ne (DTNBl) c 4- (N,N -diphenylamino)- (P )-nitros-tyrene (DPANST) d 4,4 -di(N-carbazolyl)-4"-(2-N-ethyl-4-[2-(4-nitrophenyl)-l-azo]anili-noethoxyl-triphenylamine (DRDCTA) e carbazole trimer... 

Harris KD, Ayachitula R, Strutz SJ, Hayden LM, Twieg RJ. Dual-use chromophores for photorefractive and irreversible pho-tochromic applications. Appl Opt 2001 40(17) 2895-901. 

In earlier investigations by the author [1,2] an additional nonlinear optical chromophore, (IV), and charge transport agent, (V), respectively, were prepared and used in photorefractive applications. 

S.R. Marder, B. Kippelen, A.K.Y. Jen, N. Peyghambarian, Design and Synthesis of Chromophores and Polymers for Electro-Optic and Photorefractive Applications , Nature, 388, 845 (1997)... 

For several decades, the fields of photoconducting (75) and purely electrooptic polymers (74) have been very active but had almost no direct overlap. With the development of photorefractive polymers in the early nineties, the knowledge of these two research areas could be combined and has led to a rapid improvement of the performance of existing photorefractive polymers. The photorefractive polymer composite DMNPAA PVK ECZ TNF (DMNPAA 2,5 -dimethyl-4-(p-nitrophenyl-azo)anisole PVK poly(N-vinylcarbazole) ECZ N-ethylcarbazole TNF 2,4,7-trinitrofluorenone) we developed recently (P) has reached a level of performance that competes with that of the best inorganic photorefractive crystals (77,72). With the recent progress achieved in the development of new chromophores for electro-optic applications (75), the efficiency of these new materials is expected to be significantly further improved. 

Multifunctional materials will play an important role in the development of Photonics Technology. This paper describes novel multifunctional polymeric composites for applications in both active and passive photonic components. On the molecular level, we have introduced multifunctionality by design and synthesis of chromophores which by themselves exhibit more than one functionality. At the bulk level, we have introduced the concept of a multiphasic nanostructured composites where phase separation is controlled in the nanometer range to produce optically transparent bulk in which each domain produces a specific photonic function. Results are presented from the studies of up-converted two-photon lasing, two-photon confocal microscopy, optical power limiting, photorefractivity and optical channel waveguides to illustrate the application of the multifunctional optical composites. 

The TDHF approximation has been employed in conjunction with the PM3 semi-empirical formalism in work by Kim et on the /S-hyperpolarizabilities of photoconductive chromophores. It was noted that the optical non-linearities of dipolar photoconductive molecules with carbazole, indole or indoline as donor units are large enough to be useful in electro-optic and photorefractive applications. 

Because of the versatility of the polyurethane system it is possible to introduce comonomers which can affect the physical properties of the derived polymers. For example, photo cross-linkable polyurethanes are formulated using 2,5-dimethoxy-2,4 -diisocyanato stilbene as a monomer (76). Comonomers, having an azoaromatic chromophore, are used in optical bleaching applications (77), or in the formation of photorefractive polymers (78). The latter random poljnners have second-order nonlinear optical (NLO) properties. Linear poljnners are also obtained from HDI/PTMG and diacetylenic diols. These polymers can be cross-linked through the acetylenic linkages producing a network polymer with properties similar to poly(diacetylenes) (79). 

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