Abstract: While literally the word photorefraction may describe all kinds of photo-induced changes of the refractive index of a material and therefore any photo-induced phase grating would belong to this category, it has become customary in the literature to consider only a smaller class of materials as being photorefractive. These materials possess two important properties: they are photoconductive and exhibit an electro-optic effect. Photoconductivity ensures charge transport, resulting in the creation of a space-charge distribution under inhomogeneous illumination. The electro-optic effect translates the internal electric fields induced by the inhomogeneous space-charges into a modulation of the material refractive index. This is the main mechanism for photorefraction in inorganic and organic crystals [1]. In polymers and liquid crystals, the concept of photorefraction has been expanded to include refractive index changes governed by a field-assisted molecular reorientation of the chromophores. The photorefractive effect is also distinguished from many other mechanisms leading to optically induced refractive index gratings by the fact that it is an intrinsically non-local effect, in the sense that the maximum refractive index change does not need to occur at the spatial locations where the light intensity is largest.
Publication Year: 2015
Publication Date: 2015-07-30
Language: en
Type: book-chapter
Indexed In: ['crossref']
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Cited By Count: 5
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