共查询到20条相似文献,搜索用时 15 毫秒
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Subwavelength-resolution phase images of phase dislocations at the focal region of a 20x , 0.4-N.A. lens have been obtained by use of an optical fiber interferometer with a tapered probe in one arm. A phase-stepping algorithm is used to determine a quantitative value of the phase at each point in the scan, clearly showing the presence of edge dislocations between the Airy rings of the diffraction pattern near the lens focus, as well as four isolated screw-type singularties caused by astigmatism in the lens. 相似文献
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A. G. Ushenko 《Optics and Spectroscopy》2000,89(4):597-600
The formation of a fine polarization structure of biospeckles of derma is studied. In the case of scattered laser radiation, the degree of polarization is shown to be an integrated characteristic of randomly distributed types and forms of polarization of an ensemble of biospeckles. A method for phase compensation of the degree of depolarization is proposed, which makes possible a severalfold increase of the measurement sensitivity. 相似文献
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Focusing properties of the azimuthally polarized axisymmetric Bessel-modulated Gaussian beam with Quadratic Bessel Gaussian (QBG beam) and annular aperture are investigated theoretically by vector diffraction theory. Simulation results show that the intensity distribution in focal region of the azimuthally polarized axisymmetric QBG beam can be shifted along optical axis considerably by changing parameter (C). On introducing annular aperture (δ), focal pattern at the focus extends along optical axis. In this paper, we have shown the generation of focal hole and focal shifting in the axial direction of incident beam propagating through aligned optical system which is suitable for application such as optical manipulation and optical trapping. 相似文献
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Focusing properties of the radially polarized axisymmetric Bessel-modulated Gaussian beam with quadratic radial dependence (QBG beam) and annular aperture are investigated theoretically by vector diffraction theory. Simulation results show that the intensity distribution in the focal region of the radially polarized axisymmetric QBG beam can be adjusted considerably by small beam parameter (μ) and annular aperture (δ). When μ increases, the focal spot may change to focal hole and changes focal pattern remarkably. On introducing annular aperture, focus can split or extends along the optical axis for different μ. In this paper, we have shown the generation of the focal spot, dark focal spot, focal split and increase in focal depth in the axial direction of the incident beam propagating through the aligned optical system. 相似文献
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V. A. Astapenko 《Russian Physics Journal》2011,54(6):649-657
Within the limits of a new approach based on the Mie scattering theory, polarization bremsstrahlung radiation (PBR), arising
during electron scattering on a metallic nanosphere with radius from 10 to 100 nm placed in a dielectric medium is theoretically
investigated. The spectral range close to the plasmon resonance is considered, where the contribution of the polarized channel
to bremsstrahlung radiation dominates. Spectral, velocity, and angular PBR characteristics are calculated. The sensitivity
of the PBR spectrum to the dielectric permittivity of the medium surrounding the nanosphere is demonstrated. 相似文献
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研究了用德拜公式对异常空心这类新型光束经过光阑透镜后的聚焦特性.结果表明,异常空心光束的形状一般不能保持传输不变性,但选择合适的截断参数和球差异常空心光束在一定位置可保持其初始光强分布近似不变.在焦区位相奇点会出现移动、产生和湮灭,并与截断参数、球差和光阑透镜半角有关.当无球差时,出现鞍点,奇点对的湮灭过程与鞍点对湮灭相伴发生,导致亚波长结构.用计算例对结果做了说明,并与文献中已有工作做了比较.
关键词:
异常空心光束
球差光阑透镜
位相奇点 相似文献
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V. P. Silin 《JETP Letters》1998,67(5):329-333
The polarization of the high harmonics generated in plasmas by the bremsstrahlung of electrons oscillating under the influence
of high-power plasma-heating electromagnetic radiation is described on the basis of a simple model of a cold plasma. It is
shown that when the polarization of the heating radiation differs from plane polarization by a small but finite amount, the
high harmonics are generated with almost perpendicular polarization, and the degree of circular polarization of the harmonics
increases with the number of the harmonic.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 5, 313–316 (10 March 1998) 相似文献
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Transition radiation of a relativistic charged particle intersecting a thin biconvex lens has been analyzed. The trajectory of the uniformly moving particle coincides with the optical axis of the lens. The intensity of the transition radiation in the focal plane of the lens has been estimated. 相似文献
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Based on Wolf's general tensorial theory of coherence, in which the vector nature of electromagnetic fields is considered, the closed-form propagation equation of vector Gaussian-Schell-model (GSM) beams passing through a paraxial optical ABCD system is derived, which shows the general applicable advantage, and is used to study polarization changes of GSM beams in passage through a thin lens. It is found that polarization changes are dependent on the propagation distance, focal length of the lens, beam and coherence parameters and bandwidth of the source spectrum in general. A comparison with the previous results is also made. 相似文献
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Based on Wolf's general tensorial theory of coherence, in which the vector nature of electromagnetic fields is considered, the closed-form propagation equation of vector Gaussian-Schell-model (GSM) beams passing through a paraxial optical ABCD system is derived, which shows the general applicable advantage, and is used to study polarization changes of GSM beams in passage through a thin lens. It is found that polarization changes are dependent on the propagation distance, focal length of the lens, beam and coherence parameters and bandwidth of the source spectrum in general. A comparison with the previous results is also made. 相似文献
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In order to test the predictions of the general theory for the polarization of atomic radiation excited by electron impact, we measured the polarization of atomic lines in electron-alkali atom crossed-beam experiments. The results show a typical behaviour for the polarization of lithium and sodium resonance lines, which is contrary to the earlier measurements such as those ofSkinner andAppleyard: the polarization of the resonance lines increases monotonically from higher energies to the excitation threshold. The threshold polarization of the first resonance lines of Li6, Li7 and Na23 is in good agreement with the calculations byFlower andSeaton. These results demonstrate that polarization is very sensitive to the natural level width, and to the fine and hyperfine structure separations of the excited states. Polarization of further lines has been investigated: an alkali line from anS to aP state is unpolarized as expected, but the polarization of a line from aD to aP state decreased in an unexpected manner near the threshold energy. 相似文献
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A formula has been found for the value of the induced thermal lens focus in a cell containing liquids with low absorption coefficients, inside a laser cavity. Refraction laws, and in extent, transport equations for progressive and regressive waves with gaussian profile, have been obtained in the geometrical optics approximation. The stationary case is considered, with energy transfer by conduction. The relationship found is compared with results from other works and discussed. 相似文献
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T R Seshadri 《Pramana》1999,53(6):963-969
In re-ionized models, the measurement of polarization of CMBR can be a good criterion to narrow down the parameter space for
cosmological models. A Vishniac-type effect in second order polarization over arc minute scales has been calculated. It has
been shown that while the effect is very small (∼10−2
μK) for CDM models, it can be significant (∼0.3μK) for some isocurvature models. 相似文献
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A. L. Sokolov 《Optics and Spectroscopy》2000,89(3):469-475
Polarization aberrations (PAs) of laser radiation, defined as distortions of the wave-polarization characteristics, are considered within the framework of wave theory. The parameters describing these aberrations are introduced. It is established that PAs already appear in the paraxial region. PAs of a thin lens are calculated using the method of wave-polarization matrices. It is shown that, under certain conditions, the polarization state is modified at the axis of the laser beam. 相似文献
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V. G. Bagrov 《Russian Physics Journal》1965,8(5):82-85
The polarization properties of boson radiation in a magnetic field have been studied, and expressions obtained for the integral intensity of boson and fermion radiation in a magnetic field which are suitable for random energies. The investigation of boson radiation in an external field is of limited practical interest; however, from the methodological point of view it is very instructive and has already been investigated by several authors [1, 2, 4], Also of undoubted interest is the comparison of boson and fermion (electron) radiation and hence the explanation of the role of spin in radiation.In conclusion the author expresses his deep appreciation to Prof. I, M. Ternov for assistance with the work and discussion of the results. 相似文献
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A. B. Kukanov 《Russian Physics Journal》1969,12(8):1057-1062
Quantum theory is derived for the Cerenkov radiation of an electron in a transparent uniaxial crystal. Studies are made of the cases in which the electron is initially moving parallel to and perpendicular to the optic axis. The polarization of the radiation is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 8, pp. 108–114, August, 1969.In conclusion the author thanks professor A. A. Sokolov for discussion of these results. 相似文献