Electrooptics, optimization

Banach MJ, Alexander MD Jr, Caracci S, Vaia RA. 1999. Enhancement of electrooptic coefficient of doped films through optimization of chromophore environment. Chem Mater 11 2554 2561. 

Chen, A., K. Kaviani, A. Remple, S. Kalluri, W.H. Steier, Y. Shi, Z. Liang, and L.R. Dalton. 1996. Optimized oxygen plasma etching of polyurethane based electrooptic polymers for low loss waveguide fabrication. J Electrochem Soc 143 3648-3651. 

The main limitation to general deployment of organic electrooptic materials is that they have been optimized to this point in time for applications at telecommunication wavelengths. Inorganic materials such as lithium niobate are still the materials of choice for applications at visible wavelengths. Such inorganic modulators are likely going to continue to dominate the laboratory market for modulators to be used with research laser systems. 

In conclusion, we emphasize that the area of liquid crystal applications is rapidly expanded, and a more or less informative introduction to the subject requires writing a special book. However, we hope that this chapter covers the general trends in the development of liquid crystal devices. Further progress depends on the development of new electrooptical effects and optimal liquid crystal materials to meet the ever-growing demands of technology. 

The current (third) period, which may be called a colonization, involves wide electrooptical investigations of novel effects in ferroelectric liquid crystals [9, 10] and a study of exotic materials like polymeric and lyotropic mesophases, blue phases in cholesterics, well-ordered smectics, and so on. For conventional (nematic and cholesteric) phases the accent was shifted to the optimization of the material properties for electrooptical devices, though novel phenomena like the supertwist effect [11] and a gamma of linear electrooptical effects [12-14] have also been discovered. 

A major challenge in the last few years remained the development of materials that combine the processability of polymers with the defined optical and electrical properties of low molecular weight chromophores. Strategies to optimize electrooptical and mechanical properties in OLEDs have generally implemented the use of chromophores with defined conjugation length either inserted in the polymer backbone or alternatively... 

Although the structure/property relationships have become more evident for alkyl substituted polythiophenes, the synthesis and characterization of new heterofunctionalized polythiophenes continues to be an active research area because there are a number of potential applications for new materials. There is still much to be learned about the structure/property relationships in these functionalized polymers. The effects of these side chains on the stability, solubility and self-assembly of these polymers as well as their effects on the electronic, optical and electrooptical properties are largely unknown. An improved understanding of the structure/property relationships will, in turn, drive the rational synthesis of new, functionalized polymers with optimized properties. 

The flexoelectrooptic effect is a field-sensitive electrooptic effect (it follows the sign of the field), which is fast (typically 10-100 p.s response time) with two outstanding characteristics. First, the induced tilt (p has an extremely large region of linearity, i.e., up to 30° for materials with dielectric anisotropy Ae=0. Second, the induced tilt is almost temperature-independent. This is illustrated in Fig. 39 for the Merck cholesteric mixture TI 827, which has a temperature-independent pitch but not designed or optimized for the flexoelectrooptic effect in other respects. 

We begin this section with a rdsum of the available LMM FLC materials. Due to the intense RAD efforts to commercialize FLC displays during the last S years, there has been a strong demand for suitable FLC mixtures. Chemists have respon d to this challenge and have designed materials with properties adapted and optimized for the electrooptic effect used. For this purpose the following strategy is pursued ... 

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