15 March 2001 Interband photorefractive effects and applications
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Proceedings Volume 4358, Optics of Crystals; (2001) https://doi.org/10.1117/12.418835
Event: Optics of Crystals, 2000, Mozyr, Belarus
Interband photorefractive gratings can be generated by illumination of an electro-optic crystal in the high absorption spectral region. In contrast to conventional photorefractive effects that rely on mid-gap doping levels, the gratings induced by such interband phototransitions exhibit a much faster response time (approximately equals 10 microsecond(s) at 1 W/cm2 in KnbO3) and are very robust with respect to intense illumination at sub-bandgap wavelengths. Due to the large light absorption, the interband gratings are limited to a relatively thin layer (typically 100-200 micrometers ) at the crystal surface. We discuss the main differences existing between conventional and interband photorefractive gratings. Besides by the electro-optic coefficients and the effective carrier mobilities, the strength of the gratings in a given crystal is controlled by the light intensity and the laser wavelength. Unlike in the conventional case, the photoconductivity and response speed depend here on the square-root of the light intensity. Interband photorefractive effects are interesting for applications of an optical incoherent-to-coherent converter and of an optical Joint Fourier Transform correlators based on interband dynamic holography. Finally we describe the use of this effect for creating robust and fast reconfigurable light induced waveguides in KnbO3.
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Germano Montemezzani, P. Bernasconi, Ph. Dittrich, Roland Ryf, Peter Guenter, "Interband photorefractive effects and applications", Proc. SPIE 4358, Optics of Crystals, (15 March 2001); doi: 10.1117/12.418835; https://doi.org/10.1117/12.418835

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