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Mg:Fe:LinbO_3晶体光折变增强效应的研究 总被引:2,自引:0,他引:2
在铌酸锂晶体中掺MgO和Fe2O3,生长出Mg:Fe:LiNbO3晶体.由于薄晶片的光爬行效应,晶体的二波耦合指数增益系数高达80cm-1,且角度响应范围加宽,响应速度和抗光散射能力都比Fe:LiNbO3有较大改善.以Mg:Fe:LiNbO3晶体作光放大器,实现了一次迭代全息关联存储. 相似文献
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报道了Fe:LiNbO3晶体的生长。测试了晶体的放大率,指数增益系数,衍射效率相位共轭反射率和响应时间;对Fe:LiNbO3晶体的光折变机理进行探讨。 相似文献
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在LiNbO3中掺进ZnO和Fe2O3生长了Zn:Fe:LiNbO3晶体,测试了晶体抗光致散射能力和响应时间,以Zn:Fe:LNbO3晶体为位相共轭镜,氦氖气体激活介质,构成了外泵浦位相共轭激光器。 相似文献
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双掺杂Zn,Fe:LiNbO3晶体的二波耦合效应的研究 总被引:8,自引:0,他引:8
在固液同成分LiNbO3中,同时掺入6%ZnO(摩尔比)和0.05%Fe2O3(摩尔比),用提拉法生长了双掺杂Zn,Fe,LiNbO3晶体,这是一种性能优良的光折变晶体材料。文章用二波耦合技术研究了晶体的耦合增益和衍射效率,Zn,Fe:LiNbO3的光致折射率变化值达10^-5,且响应速率达到秒量级,这是双掺Zn,Fe两种杂质共同作用的结果。 相似文献
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Zn:Fe:LiNbO3晶体的生长及位相共轭效应的研究 总被引:4,自引:0,他引:4
在LiNbO3中掺进ZnO和Fe2O3生长出Zn:Fe:LiNbO3晶体。测试了晶体抗光致散射能力、位相共轭反射率和响应时间。研究了Zn:Fe:LiNbO3位相共轭效应增强的机理。 相似文献
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屈光介质中谱域光学相干层析成像的重构 总被引:2,自引:2,他引:2
在屈光介质中,由于光线的折射以及光程与实际物理距离的错配,使得光学相干层析(OCT)成像存在重构误差。将几何光学中光线追迹的方法应用于光纤型谱域光学相干层析成像系统所成图像的重构误差矫正,在理论上推导了屈光介质所成层析图像与其真实物理结构的映射关系。实验中,将提出的方法应用于玻璃毛细管和人眼眼前节图像的重构误差矫正,在矫正后的图像中玻璃毛细管的剖面结构得到了准确的还原,所测人眼的眼角膜厚度、前房深度和宽度、眼角膜前后表面以及晶状体前表面的曲率半径等各种参数都符合模型眼给出的参考值。该方法能够使光学相干层析成像系统应用于具有任意多层折射界面的屈光介质,包括由透镜组组成的复杂光学系统等的成像。 相似文献
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A. S. Il’inskii T. N. Galishnikova 《Journal of Communications Technology and Electronics》2016,61(9):981-994
Problems on reflection of a plane electromagnetic wave from various irregular interfaces between media are studied by the integral equation method in the cases of two- and three-dimensional incident electromagnetic field. The reflecting surfaces are meant as periodic transparent interfaces between two media and plane boundaries with locally inhomogeneous and transparent sections. The boundary value problems for the system of Maxwell’s equations in an infinite domain with an irregular boundary are reduced to Fredholm or singular integral equations, depending on the problem considered. Numerical algorithms for solving such integral equations are developed. Results of calculation of currents induced on inhomogeneities and characteristics of the electric field in the far zone are presented.Problems on reflection of a plane electromagnetic wave from various irregular interfaces between media are studied by the integral equation method in the cases of two- and three-dimensional incident electromagnetic field. The reflecting surfaces are meant as periodic transparent interfaces between two media and plane boundaries with locally inhomogeneous and transparent sections. The boundary value problems for the system of Maxwell’s equations in an infinite domain with an irregular boundary are reduced to Fredholm or singular integral equations, depending on the problem considered. Numerical algorithms for solving such integral equations are developed. Results of calculation of currents induced on inhomogeneities and characteristics of the electric field in the far zone are presented. 相似文献
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This paper proposes a novel robust video watermarking scheme based on local affine invariant features in the compressed domain. This scheme is resilient to geometric distortions and quite suitable for DCT-encoded compressed video data because it performs directly in the block DCTs domain. In order to synchronize the watermark, we use local invariant feature points obtained through the Harris-Affine detector which is invariant to affine distortions. To decode the frames from DCT domain to the spatial domain as fast as possible, a fast inter-transformation between block DCTs and sub-block DCTs is employed and down-sampling frames in the spatial domain are obtained by replacing each sub-blocks DCT of 2×2 pixels with half of the corresponding DC coefficient. The above-mentioned strategy can significantly save computational cost in comparison with the conventional method which accomplishes the same task via inverse DCT (IDCT). The watermark detection is performed in spatial domain along with the decoded video playing. So it is not sensitive to the video format conversion. Experimental results demonstrate that the proposed scheme is transparent and robust to signal-processing attacks, geometric distortions including rotation, scaling, aspect ratio changes, linear geometric transforms, cropping and combinations of several attacks, frame dropping, and frame rate conversion. 相似文献
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Blacknell D. Freeman A. White R.G. Wood J.W. 《Geoscience and Remote Sensing, IEEE Transactions on》1987,(6):775-782
The synthetic aperture radar (SAR) is an imaging system that achieves high azimuthal resolution by tracking individual point scatterers using their phase histories, with the expected phase history of a particular point scatterer being derived from the assumed motion of the airborne SAR platform. Normally, it is assumed that the platform travels along a straight line path and that the radar pulses are emitted at equal spatial intervals. However, the aircraft carrying the SAR will be susceptible to extraneous across tracl motions and errors in the pulse spacing also may occur. These errors manifest themselves. as two forms of image degradation in the final image. Firstly, the image will be defocused due to an error in the expected quadratic phase history, and secondly, the image will contain geometric distortions due to an error in the linear phase history. An autofocus technique can be used to focus the image and produce a measure of the quadratic phase error that in turn can be used to estimate the geometric distortions that will be present in the final image. These distortions can be independently measured by direct comparison with a map of the imaged area. This paper describes the application of these methods to some real SAR data and discusses the results of the comparison of the measurements of autofocus and geometric distortions in terms of both the likely platform motions present and the viability of predicting geometric distortion using the autofocus measurements. 相似文献
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电信管制政策历来是基于传统业务类型划分,然而,技术和市场融合与新技术的涌现正在改变电信政策的制定和实施环境,从而导致政策在相似服务之间的不一致性和相应的政策扭曲,主要表现在市场竞争、技术、投资、互联和普遍服务等若千方面。通过引入一个与未来TCP/IP网络相对应的分层政策模型.例如将网络分为内容层、业务层、传输层和接入层,并以此为基础考虑政策制定和实施,可以解决以上所述扭曲和政策不一致性问题,从而更有效地促进市场竞争. 相似文献
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Simple methods that compensate for low- and highfrequency delay distortions, which are the predominant distortions in a baseband hybrid digital transmision line, have been developed. Compensation for low frequency distortion is optimized by a rational minimum-phase function. Compensation for high-frequency distortion is attained by a combination of an optimum cutoff shape and an all-pass network. A local minimum problem in the optimization of the all-pass network is eliminated by a procedure that provides appropriate initial conditions. Combined realization of both low- and high-frequency delay compensation by a slightly active network results in very simple circuitry. The efficiency of this simple compensator is confirmed experimentally in a subline with 15 analog repeaters. In this experimental system, two subpredominant distortions, nonlinear distortion and equalization error, were experienced. Compensation for these distortions is also studied by the method reported in the literature and by a simple adaptive equalizer, respectively. Based on the results obtained above, the feasibility of a baseband hybrid digital transmission system is discussed. The simple compensator mentioned above will be very useful in realizing an economical hybrid digital transmission system with the help of the simple adaptive equalizer. A system that utilizes alternate mark inversion (AMI) pulse train seems to be feasible without the help of the adaptive equalizer. 相似文献
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Andreev N.F. Khazanov E.A. Kuznetsov S.V. Pasmanik G.A. Shklovsky E.I. Sidorin V.S. 《Quantum Electronics, IEEE Journal of》1991,27(1):135-141
Theoretical and experimental results obtained in the study of phase-locked conjugation of two light beams using a phase synchronizer demonstrate how phase conjugation of depolarized radiation can be used to compensate aberration and depolarization distortions in solid-state media. Two-beam phase conjugation via mutual scattering of orthogonally polarized pump waves under four-wave mixing is discussed. A novel analog operation-orthogonal phase conjugation (OPC)-involving an electromagnetic field was realized with a phase synchronizer 相似文献