Off-Bragg-angle light diffraction and structure of dynamic interband photorefractive gratings |
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Authors: | P. Bernasconi G. Montemezzani P. Günter |
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Affiliation: | Nonlinear Optics Laboratory, Institute of Quantum Electronics, Swiss Federal Institute of Technology, ETH H?nggerberg, CH-8093 Zürich, Switzerland (Fax: +41-1/633-1056, E-mail: pbernasc@iqe.phys.ethz.ch), CH
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Abstract: | Steady-state and time-resolved off-Bragg-angle diffraction experiments are used to determine the structure and the dynamics of photorefractive gratings induced by interband photoexcitation. In potassium niobate, we identify in such gratings basically a two-layer structure. Close to the surface, we find a space-charge electric field generated by a charge modulation stored directly in the bands. This grating component is typically 50 μm thick, the amplitude of the refractive index modulation is larger than 10-4, and the response time is a few μs for resonant intensities of 100 mW cm-2. This component is also robust under non-resonant illumination. Deeper in the crystal, a second holographic layer extends over a few hundreds of μm, its amplitude is smaller, and its slower response time is in the ms range. The mutual phase shift between the grating components is also determined. Received: 23 November 1998 / Revised version: 14 January 1999 / Published online: 12 April 1999 |
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Keywords: | PACS: 42.40.Lx 42.65.Hw 77.84.Dy |
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