The exact energy flow pattern on the axis of a circular disk by transient excitation is presented in this paper. It has been shown that non-decaying region does not appear when the source is chosen to be a rectangular...The exact energy flow pattern on the axis of a circular disk by transient excitation is presented in this paper. It has been shown that non-decaying region does not appear when the source is chosen to be a rectangular pulse, on the contrary, there exists a uprising region on the axis when the width of the pulse is less than a/c. After reaching its maximum value point, the energy decays slowly until the law of r-2 is met. The scale of the uprising region is dependent upon the size of the antenna and the width of the pulse. It has also been shown that there exists a oscillatory region near the source for a harmonic excitation, and the amplitude is also uprising, which is quite different compared with the conclusion drawn by S. Silver(1949). Finally, the phenomenon of energy uprising in time domain is explained and some problems about the electromagnetic missiles are also expounded.展开更多
After the three-dimensional self-affine fractal random surface simulation, we use the optical scattering theory to calculate the deep Fresnel region speckle(DFRS) under consideration of the more strict shadowing effec...After the three-dimensional self-affine fractal random surface simulation, we use the optical scattering theory to calculate the deep Fresnel region speckle(DFRS) under consideration of the more strict shadowing effect. The evolution of DFRS with the scattering distance and the intensity probability distribution are studied. It is found that the morphology of the scatterer has an antisymmetric relationship with the intensity distribution of DFRS, and the effect of micro-lenses on the scattering surface causes the intensity probability distribution of DFRS to deviate from the Gaussian speckle in the high light intensity area.展开更多
We report a heptad vortex array structure in the wave fields in an extremely deep Fresnel diffraction region by asymmetrical subwavelength holes in a metal film illuminated with linearly polarized light. A Mach Zehnde...We report a heptad vortex array structure in the wave fields in an extremely deep Fresnel diffraction region by asymmetrical subwavelength holes in a metal film illuminated with linearly polarized light. A Mach Zehnder interferometer with a microscopic objective is used to record the wave fields at different distance＆ and the phase maps are extracted by Fourier transform of the interference intensities. We study the evolutions of the heptad vortex array with distance from the sample to the object plane. To explain the formations and the evolutions of the vortex array, we calculate the diffracted wave fields with Kirchhoff＇s diffraction theory. The calculations are basically consistent with the experimental results, and the properties of the heptad vortex array structure are reasonably explained.展开更多
Based on the Kirchhoff approximation and the theoretical analysis of the random light fields, the speckle intensity distributions in the extremely deep Fresnel diffraction region are simulated. The fractal property of...Based on the Kirchhoff approximation and the theoretical analysis of the random light fields, the speckle intensity distributions in the extremely deep Fresnel diffraction region are simulated. The fractal property of the speckles as well as the relation between the speckle intensity distribution and the corresponding random surface is investigated. We design a microscope system to detect experimentally the speckles in the extremely deep Fresnel diffraction region, and the experimental results prove the conclusions drawn from our simulations.展开更多
文摘The exact energy flow pattern on the axis of a circular disk by transient excitation is presented in this paper. It has been shown that non-decaying region does not appear when the source is chosen to be a rectangular pulse, on the contrary, there exists a uprising region on the axis when the width of the pulse is less than a/c. After reaching its maximum value point, the energy decays slowly until the law of r-2 is met. The scale of the uprising region is dependent upon the size of the antenna and the width of the pulse. It has also been shown that there exists a oscillatory region near the source for a harmonic excitation, and the amplitude is also uprising, which is quite different compared with the conclusion drawn by S. Silver(1949). Finally, the phenomenon of energy uprising in time domain is explained and some problems about the electromagnetic missiles are also expounded.
文摘After the three-dimensional self-affine fractal random surface simulation, we use the optical scattering theory to calculate the deep Fresnel region speckle(DFRS) under consideration of the more strict shadowing effect. The evolution of DFRS with the scattering distance and the intensity probability distribution are studied. It is found that the morphology of the scatterer has an antisymmetric relationship with the intensity distribution of DFRS, and the effect of micro-lenses on the scattering surface causes the intensity probability distribution of DFRS to deviate from the Gaussian speckle in the high light intensity area.
基金Supported by the National Natural Science Foundation of China under Grant No 11574185the Science and Technology Development Program of Shandong Province under Grant No 2009GG10001005
文摘We report a heptad vortex array structure in the wave fields in an extremely deep Fresnel diffraction region by asymmetrical subwavelength holes in a metal film illuminated with linearly polarized light. A Mach Zehnder interferometer with a microscopic objective is used to record the wave fields at different distance＆ and the phase maps are extracted by Fourier transform of the interference intensities. We study the evolutions of the heptad vortex array with distance from the sample to the object plane. To explain the formations and the evolutions of the vortex array, we calculate the diffracted wave fields with Kirchhoff＇s diffraction theory. The calculations are basically consistent with the experimental results, and the properties of the heptad vortex array structure are reasonably explained.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.10974122 and 10874105)the Science and Technology Research Project of Shandong Province of China(Grant No.2009GG10001005)+1 种基金the Shandong Distinguished Middleaged and Young Scientist Encourage and Reward Foundation,China(Grant Nos.2007BS04031 and BS2009SF020)the State Key Development Program for Basic Research of China(Grant No.2006CB806003)
文摘Based on the Kirchhoff approximation and the theoretical analysis of the random light fields, the speckle intensity distributions in the extremely deep Fresnel diffraction region are simulated. The fractal property of the speckles as well as the relation between the speckle intensity distribution and the corresponding random surface is investigated. We design a microscope system to detect experimentally the speckles in the extremely deep Fresnel diffraction region, and the experimental results prove the conclusions drawn from our simulations.
