A new class of strongly photorefractive materials

Certain doped compound semiconductors exhibit persistent photoconductivity (PPC) at low temperatures as a result of the optical ionization of electrons from deep, spatially localized, donor levels known as DX centers. We calculate that this release of carriers also produces a refractive index shift (through the plasma effect) which is 30 times larger than that of conventional photorefractive materials, We report the results of diffraction measurements on samples of AlGaAs which support this prediction. The induced index changes can be erased by heating above an annealing temperature determined by the material composition.<
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