Photoconductivity and Electro-Optic Responses

Photoconductivity can be estimated by a DC photocurrent method that measures the light-induced change in the current through the sample under illumination. If a photoconductor is irradiated with appropriate radiation, carrier generation, and recombination will take place. If/ph is the photocurrent density (A cm ) measured under an electric field E (V cm ), the photoconductivity cm ) is given by 

The number of generated charges per absorbed photon, called the internal quantum efficiency, is given by Equation 8.9 [65]. 

Here I is the intensity of incident light, L is the thickness of the photoconductor, a is the absorption coefficient, and X is the wavelength of light. If /ph is the photocurrent, Po is the light power density, A is the illuminated area, and V is the applied voltage, the change in conductivity per incident light intensity, called 

Other methods for the determination of carrier mobility include holographic time of flight (HTOF) and extraction current transients [67, 68]. The density of traps may be estimated with near-IR optical absorption in the case of Cgo-sensitized PVK systems [69] or can be estimated from thermally stimulated discharge current measurements [70]. 

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In materials that possess both photoconductive and electro-optic responses, the photo-generation and trapping of charge carriers produces internal fields that modify the refractive index. A sinusoidally varying intensity caused by the... 

PhotMefractive (PR) polymers are multifunctional field-responsive materials that combine photoconducting and electro-optic propoties. hi this charter, we will review the basics of photorefiactivity in polymers and liquid crystals and describe recent advances that have led to highly efficient materials. These advances in material development enable a variety of photonic aiqilications including optical correlators for security verification. 

Among the various material systems that make up smart pixels, liquid crystals are particularly interesting because of their transparency, broadband electro-optical response, and other unique material properties. Liquid crystal on silicon (LCOS) devices, liquid crystal spatial light modulators (LCSLMS), incorporating neural net functions enabled by the backplane electronics and inter- and intrapixel electronic cormections, such as optoelectronic neuron array, LC/silicon retina, and winner take-all circuit, have been developed previously. In these devices, the photosensitivity needed for sensing the input comes from the photoconductive layer processed into... 

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