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We carried out detailed calculations for photorefractive wave-mixing switches based on one of three crystals with high electro-optic coefficients, namely, BaTiO3, Strontium Barium Niobate (SBN (0.75)), and Potasium Sodium Strontium Barium Niobate (KNSBN). A comparison of results for the three crystals shows that a 0_-cut BaTiO3 crystal is suitable for a longitudinal switch and requires a voltage of about 80 for a 2-mm-thick crystal to induce sufficient phase mismatch. The electrodes must be transparent for the incident and diffracted beams. A 45_-cut SBN (0.75) crystal, however, is suitable for a lateral switch and requires a voltage of about 150 for a 1-mm-wide crystal. The electrodes do not need to be transparent. 相似文献
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D. Nelis K. Van Werde D. Mondelaers G. Vanhoyland H. Van den Rul M.K. Van Bael J. Mullens L.C. Van Poucke 《Journal of Sol-Gel Science and Technology》2003,26(1-3):1125-1129
The synthesis of multimetal oxides containing pentavalent elements like Nb and Ta out of an aqueous solution is very complicated due to the extremely high sensitivity of these metals towards hydrolysis. Moreover the only water-soluble starting compound is the oxalate which is not very suited for gel formation. Nevertheless, from Nb-oxalate it is possible to prepare a water-soluble Nb(V)-precursor by chemical modification. The synthesized precursor remains stable in the pH-range needed for gel formation. This Nb(V)-precursor is used for the synthesis of the ferroelectric material SrBi2Nb2O9 (SBN). An aqueous acetate-citrate solution-gel precursor for SBN was prepared. The chemical homogeneity of this precursor was investigated by means of TEM-experiments. All metal ions were found to be homogeneously dispersed in the precursor gel at least down to 10 nm. The SBN phase formation is followed by means of X-ray Diffraction. It has been shown that the perovskite phase already forms at 550°C. 相似文献
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INVESTIGATION OF PHOTOREFRACTIVE TWO-WAVE COUPLING IN Cr-DOPED STRONTIUM BARIUM NIOBATE CRYSTAL 总被引:1,自引:0,他引:1
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We present here the experimental results of photorefractive two-wave coupling in the congruent strontium barium niobate (SBN:61) crystal doped with 1000ppm Cr. Employing a He-Ne laser (632.8nm), we observed the coupling characteristics under different conditions. The crystal shows excellent photorefractive properties, with a high coupling coefficient nearly 6cm-1 as the beam intensity ratio m is less than 100. The saturated coupling coefficient of SBN:61:Cr shows a maximum at a certain external beam crossing angle 2θpeak, which varies with different m, showing a nearly linear dependence on m. The saturated coupling response time τ is measured to be less than 0.8 s. The response time decreased with increasing beam crossing angles no matter how large m is. We also observed the behaviour of the probe beam in reversed experimental procedures. We found that the probe beam shows a bistable state in both procedures. 相似文献
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Light-induced scattering in SBN:Cr crystal under external electric fields and its suppression
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In this paper, the enhancement of light-induced scattering in congruent SBN:Cr (Sr_{0.61}Ba_{0.39}Nb_2O_6:Cr) crystals in the presence of an externally applied electric field and its suppression are studied. If a coherent image is focalized in SBN:Cr crystal without applying external electric field, the output image will remain clear, because of the weak photorefractive effect in the crystal. When a field is applied properly along the crystal axis, markedly enhanced scattering from the signal beam and the output image dispersion can be observed due to the increase of the photorefractive two-beam coupling gain and the light-induced index change in SBN:Cr crystals. By introducing a coherent or incoherent beam with higher intensity the light-induced scattering can be suppressed through the erasure of scattering gratings. The difference between coherent and incoherent beam is that the former can also amplify the signal beam as the scattered light is removed, whereas the latter can only make the signal beam revert to its initial state. The results obtained under different experimental conditions are consistent with theoretical analysis. 相似文献
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对固液同成分SBN:Cr(Sr0.61Ba0.39Nb2O.6:Cr)晶体在外加直流电场作用下的光折变二波耦合特性及其应用进行了实验研究,分析了晶体的二波耦合强度增益 系数随外电场变化的趋势,并给出了实验测量结果.发现在适当的外电场作用下,晶体的光折变二波耦合增益和响 应速度可以得到一定程度的提高.进一步的研究表明,这种电场响应特性有助于改善SBN:Cr晶体的某些应用性能.利用该晶体通过光折变二波耦合非线性放大原理实现光学图像边沿增强时,通过给晶体沿轴向施加适当的外电场,可进一步提高图像边沿增强效果;在基于光 折变边沿增强预处理的联合变换相关器中,适当的外加电场可进一步改善联合变换相关器的相关识别性能.
关键词:
SBN:Cr晶体
光折变二波耦合
边沿增强
联合变换相关器 相似文献
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Jie Lian Qingpu Wang Aijian Wei Yurong Wang Ruifeng Zhang Xingkui Cheng 《Optics & Laser Technology》2005,37(5):622-419
Cerium-doped Sr0.60Ba0.40Nb2O6 (SBN:60) crystals were obtained by Czochralski method. Optical transmission spectra were measured and the absorption coefficients were calculated in the visible range. The results showed that Ce-doped crystals were transparent for wavelengths more than and the fundamental absorption edge shifted towards the longer wavelength direction with increasing Ce concentrations. In addition, the birefringence of crystals were investigated based on the theory of interference between extraordinarily and ordinarily polarized light, and the birefringence values were determined in the long wavelength region. As a result, the birefringence becomes larger by doping of SBN crystals with cerium. 相似文献
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