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The optical near-field speckles and their first order statistics on the basis of the integral equations of electromagnetic field

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Science China(Physics,Mechanics & Astronomy) 2004年第3期47卷 365-380页

作者： CHENG Chuanfu1, 2, SONG Hongsheng2, LIU Chunxiang2, REN Xiaorong2, ZHANG Ningyu3, TENG Shuyun1 & XU Zhizhan1 1. Shanghai Institute of optics and Fine Mechanics, Chinese Academy of Sciences, P. O. Box 800-211, Shanghai 201800, China 2. Department of Physics, Shandong Normal University, Jinan 250014, China 3. Shandong Institute of Architecture and Engineering, Jinan 250014, China Shanghai Institute of optics and Fine MechanicsChinese Academy of SciencesShanghaiChina Department of PhysicsShandong Normal UniversityJinanChina Shandong Institute of Architecture and EngineeringJinanChina

From Helmholtz equation of the harmonic electromagnetic waves, the integral equations of the light field at the medium boundaries are obtained by use of the Green抯 theorem and are discretized into linear equation set with the values of the light field and its derivative as the unknowns. On solving the linear equation set, we realize the rigorous computations of the light fields at the boundaries. Then the intensities of the light waves scattered by the random self-affine fractal surfaces in the optical near-field are calculated, and the propagation characteristics, the evolutions of the contrast and the intensity probability density function of the near-field speckles are studied in detail. The near-field speckles are much different from the conventional speckles in the diffraction regions and in the imaging systems. There are obvious local fluctuations in the intensity distributions of the near-field speckles and such fluctuations disappear after propagating a distance of one wavelength from the medium surfaces. For the random surfaces with smaller lateral correlation lengths, the speckle contrasts approach the saturation values and the speckle fields approach Gaussian distribution within the near-field, while for the random surfaces with larger lateral correlation lengths, such evolutions become comparatively slow.

关键词： speckle, near-field optics, first order statistics, Green's function.

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The electromagnetically induced transparency in the Y-type four-level atom system at low light levels

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Science China(Physics,Mechanics & Astronomy) 2005年第5期48卷 593-599页

作者： ZHANG Liying LIU Zhengdong CHEN Jun Institute of Modern Physics Nanchang University Nanchang 330047 China Institute of Modern Physics Nanchang University Nanchang 330047 China Institute of Modern Physics Nanchang University Nanchang 330047 China

In this paper a Y-type four-level atom interacting with external fields system is investigated. It is shown that increasing the control field can reduce the probe absorption, the electromagnetically induced transparency (EIT) and gain can be obtained if the parameters are taken appropriately. An interesting phenomenon is found that the system appears to be probe gain in a large region if the external fields Rabi phases are taken appropriately, too.

关键词： quantum optics, the nonlinear effect at low light levels, EIT, spontaneous emission, quantum interference.

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Simulation study of phase retrieval for hard X-ray in-line phase contrast imaging

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Science China(Physics,Mechanics & Astronomy) 2005年第4期48卷 450-458页

作者： YU Bin1,2, PENG Xiang1,2, TIAN Jindong1, NIU Hanben1, DIAO Luhong3 & LI Hua3 1. Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education, Institute of Optoelec- tronics, Shenzhen University, Shenzhen 518060, China 2. State Key Laboratory of Precision Measuring Technology and Instruments, Tianjin University, Tianjin 300072,China 3. Key Laboratory of Intelligent Information Processing, Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100080,China Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education Institute of Optoelectronics Shenzhen University Shenzhen China State Key Laboratory of Precision Measuring Technology and Instruments Tianjin University Tianjin China Key Laboratory of Intelligent Information Processing Institute of Computing Technology Chinese Academy of Sciences Beijing China

Two algorithms for the phase retrieval of hard X-ray in-line phase contrast imaging are presented. One is referred to as Iterative Angular Spectrum Algorithm (IASA) and the other is a hybrid algorithm that combines IASA with TIE (transport of intensity equation). The calculations of the algorithms are based on free space propagation of the angular spectrum. The new approaches are demonstrated with numerical simulations. Comparisons with other phase retrieval algorithms are also performed. It is shown that the phase retrieval method combining the IASA and TIE is a promising technique for the application of hard X-ray phase contrast imaging.

关键词： X-ray optics, phase contrast imaging, phase retrieval, angular spectrum, hard X-ray.

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A new formula on the Fresnel reflectance and its application in microwave remote sensing

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Science China Earth Sciences 2004年第11期47卷 1045-1052页

作者： XU Qing LIU Yuguang Key Laboratory of Physical Oceanography of the Ministry of Education Ocean University of China Qingdao 266003 China Key Laboratory of Physical Oceanography of the Ministry of Education Ocean University of China Qingdao 266003 China

A new formula on the Fresnel reflectance is derived based on our understanding of the complex index of refraction and continuity condition of the E-M waves across the interface between two media. The imaginary component of the complex index of refraction is related to the attenuation of the E-M waves propagating in a medium. It does not denote the phase of the E-M waves. The traditional derivation confuses the physical meaning of the imaginary component of the complex index of refraction. The derived formula on the Fresnel reflectance can be used to obtain the emissivity of sea surface, which is useful to retrieve sea surface temperature and sea surface salinity in the microwave remote sensing.

关键词： reflectance, refraction, microwaves, optics, remote sensing.

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Experimental realization of quantum cryptography communication in free space

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Science China(Physics,Mechanics & Astronomy) 2005年第2期48卷 237-246页

作者： WANG Chuan1, ZHANG Jingfu1, WANG Pingxiao1, DENG Fuguo1, AI Qing1 & LONG Guilu1,2 1. Department of Physics, Key Laboratory for Quantum Information and Measurements, Tsinghua Univer- sity, Beijing 100084, China 2. Center for Atomic and Molecular NanoSciences, Tsinghua University, Beijing 100084, China Department of Physics Key Laboratory for Quantum Information and Measurements Tsinghua University Beijing China Atomic and Molecular NanoSciences Tsinghua University Beijing China

Utilizing linear optical devices, the principle of B92 quantum key distribution (QKD) protocol is demonstrated in free space with a distance of transmission of 2.2 meters. The faint laser pulses with 650 nm wavelength are used as the single photon sources. The experimental results show that the eavesdropping behavior in the signal transmission can be detected. We also discuss the problems and solutions in using the quantum cryptography communication practically. It is pointed out that one of the approaches to increasing the distance of the quantum communication is to overcome the attenuation of the single photon in transmission. This could not be solved by the use of single photon source, and new quantum communication protocols are needed to solve these problems.

关键词： quantum key distribution, free space, linear optics, faint pulses.

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A Simple Method to Obtain Exact Soliton Solutions for a Nonlinear Equation in a Loss Fibre System

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Communications in Theoretical Physics 2002年第11期 615-616页

作者： YANG Xiao-Xue WU Ying Department of Physics and National Key Laboratory for Laser Technique Huazhong University of Science and Technology Wuhan 430074 China Department of Physics and National Key Laboratory for Laser Technique Huazhong University of Science and Technology Wuhan 430074 China Wuhan Institute of Physics and Mathematics the Chinese Academy of Sciences Wuhan 430071 China

We show that the nonlinear equation governing wave propagation in a loss fibre system considered byNakkeeran in J. Phys. A34 (2001) 5111 can be brought into the standard nonlinear Schrodinger equation by a simpletrans...

关键词： nonlinear optics, fibre communication

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