ASIAN JOURNAL OF PHYSICS

Asian Journal of Physics                                                                                                         Vol. 4, Nos 1&2 (1995) 1-14

KNbO₃ crystals: Optimization of photorefractive response time and infrared sensitivity

C Medrano, M Zgonik, I Liakatas, M Ewart and P Gunter

Nonlinear Optics Laboratory, Institute of Quantum Electronics

Swiss Fedral Institute of Technology, ETH Honggerberg, CH-8093 Zurich, Switzerland

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Potassium niobate crystals dopped with Fe, Ni, Cu, Ce, Rh and Co were grown in order to optimize the photorefractive response over an extended spectral range. Extrinsic properties important for the photorefractive effect: absorption, and two- beam coupling, are discussed. Modification of the charge transport parameters in order to improve the response time of photoiduced refractive index changes is obtained by means of post growth annealing at temperatures of 400-900 °C in a controlled atmosphere.

Total Refs: 26

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Asian Journal of Physics                                                                                                        Vol 4. Nos 1 & 2(1995)15-29

Hexagon formation, image processing and image broadcasting using photorefractive potassium niobate

H-L Yu and P P Banerjee

Department of Electrical and Computer Engineering

University of Alabama in Huntsville, Huntsville AL 35899 USA

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We examine novel applications of photorefractive KNbO₃:Fe in hexagonal array generation, edge enhancement and image broadcasting. Edge enhancement, as well as phase conjugation, is readily achieved using a two beam coupling geometry. Pertinent theories are also discussed, especially, the instability criteria leading to hexagon generation, assuming transmission and reflection gratings.

Total Refs: 23

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Asian Journal of Physics                                                                                                       Vol 4. Nos 1 & 2(1995)31-44

Phtorefraction at 780 nm in Bi₁₂SiO₂₀ crystals: Effects and applications

S Mailis, L Boutsikaris and N A Vainos

Foundation for Research and Technology-Hellas (FORTH), Institute of Electronic Structure and Laser (IESL)

P O Box 1527, Heraklion 711 10, Greece

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Photorefractive holographic recording at 780 nm in Bi₁₂SiO₂₀ which exhibits dual,dynamic and semipermanent, behaviour is investigated. The semipermanent holograms present very long decay times (up to 3600 sec) for relatively high reading and consequently erasing beam intensities. Experimental investigation of this behavior is performed and comparison with theoretical results is made. Finally, image processing applications, such as addition and subtraction of images and incoherent-to-coherent information transfer, utilizing this dual recording character as well as the special properties of the material, are presented.

Total Refs: 24

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Asian Journal of Physics                                                                                                        Vol 4. Nos 1 & 2(1995)45-51

Effective optical nonlinearity of BSO crystals and its applications to CW optical limiting

Serey Thai, and John Malowicki

Rome Laboratory/OCPC, 25 Electronics Parkway, Griffiss AFB, New York 13341

And

Q Wang Song

Department of Electricl and Computer Engineering, Syracuse University, Syracuse, New York 13224-1240

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Photo-induced effective nonlinearity, n₂, of a BSO crystal is measured by using a Z-scan method which is based on self-focusing/defocusing effect. The Z-scan technique is an simple yet accurate way to measure, n₂. An optical limiter utilizing the photo-induced lensing is investigated and the influences of spatial self phase modulation for strong CW illumination is presented.

Total Refs: 8

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