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While in the conduction band, the electrons may with some probability recombine with the holes and return to the impurity levels. The rate at which this recombination takes place determines how far the electrons diffuse, and thus the overall strength of the photorefractive effect in that material.
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The pattern stored inside the crystal persists until the pattern is erased; this can be done by flooding the crystal with uniform illumination which will excite the electrons back into the conduction band and allow them to be distributed more uniformly.
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throughout the crystal. Since the electrons are being excited preferentially in the bright fringes, the net electron diffusion current is towards the dark-fringe regions of the material.
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diffracts the laser beams. As a result, one beam gains energy and becomes more intense at the expense of light intensity reduction of the other. This phenomenon is an example of
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to be set up in the crystal. Since the electrons and holes are trapped and immobile, the space charge field persists even when the illuminating beams are removed.
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With the net redistribution of electrons into the dark regions of the material, leaving holes in the bright areas, the resulting charge distribution causes an
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to occur throughout the crystal. The pattern of the grating that is formed follows the light interference pattern originally imposed on the crystal.
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Once back in the impurity level, the electrons are trapped and can no longer move unless re-excited back into the conduction band (by light).
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light shone into the crystal, with the resulting diffraction pattern recreating the original pattern of light stored in the crystal.
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Photorefractive materials: fundamental concepts, holographic recording and materials characterization
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between the beams results in a pattern of dark and light fringes throughout the crystal.
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beams of light. (In holography, these would be the signal and reference beams).
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beams (usually obtained by splitting a laser beam by the use of a
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Once in the conduction band, the electrons are free to move and
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The photorefractive effect occurs in several stages:
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371:Introduction to photorefractive nonlinear optics
346:Photorefractive materials and their applications
344:Peter GĂĽnter, Jean-Pierre Huignard, ed. (2007).
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373:. Wiley series in pure and applied optics.
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266:Photorefractive materials include
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122:phase-conjugate mirror
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300:multiple quantum well
319:J. Frejlich (2007).
202:electro–optic effect
369:Pochi Yeh (1993).
226:dynamic holography
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159:into the
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