Photorefractive amorphous

The Photorefractive Effect in Crystals and Amorphous Organic Media... 

The initial sensitizer anion presence makes recombination of mobile holes possible in the dark regions. Which are the compensator sites Here, there exist different explanations. One possibility is that some of the electro-optic dye molecules present in photorefractive composites to provide refractive index change may become charged positively. An alternative theory in the case of amorphous materials is that the amorphous disorder leads to defect sites forming local potential minima at which positive charge may be immobilized (Figure 5). 

More recently the promising range of applications for photorefractive materials has motivated the rapid development of amorphous, organic materials with a strong photorefractive response [5]. Here the chemical composition of the materials may be varied with relative ease and the opportunity to compare materials from different sources should exist. The various processes necessary for photorefraction may be obtained by a single material, or many different molecular species may be mixed in a composite to provide the range of properties needed. These amorphous materials do not have a well-defined mobility for the photogenerated holes that... 

Electron Transfer in Amorphous Organic Photorefractive Media 481... 

The field of photorefractivity in organic polymers and glasses has been in existence for less than a decade. The understanding of charge generation in these materials (which are often composites) is not yet mature, and the behavior of some of the more common constituents is understood better. Much of the literature on photo-refraetivity deseribes free earrier generation quantum efficiency measurements only briefly, before a more detailed discussion of other factors such as mobility and electro-optic response. Some of the relevant information pertinent to free carrier generation in these materials is presented here, to be followed by a review of this aspect of the amorphous photorefractives literature. 

Table 2. Rate of response of fast amorphous photorefractive materials a comparison of the experimental fast time constant of growth of contrast in refractive index in response to a nonuniform intensity pattern and the theoretical rate limit based on charge photogeneration rate.

An Overview of Amorphous Organic Photorefractives and Their Applications 503... 

In this section, we will first provide a short discussion on some of the basics of the design of photorefractive polymers. Then we will review some of the basic physical properties such as photogeneration and transport in organic amorphous materials needed to develop and understand photorefractive polymers. We will describe the orientational photorefractive effect that is used in most of today s low glass transition temperature materials. Finally we will describe selected examples of photorefractive polymers and describe their optical and electrical properties. 

A small molecular system based on carbazole moiety was developed for photorefractive applications. One of the molecules has b n shown to form staUe and amorphous films and exhibit good photorefractive performance. A net optical gain of 11 cm- was observed. An attractive feature of this molecule is that its photorefractive response is fast. Because of its structural versatility, this molecular system is worth further exploration. 

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