The Experts below are selected from a list of 23829 Experts worldwide ranked by ideXlab platform
Xiaofeng Li - One of the best experts on this subject based on the ideXlab platform.
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subwavelength focusing behavior of high Numerical Aperture phase fresnel zone plates under various polarization states
Applied Physics Letters, 2009Co-Authors: Rakesh G Mote, S F Yu, Wei Zhou, Xiaofeng LiAbstract:An analytical model is developed to study the subwavelength focusing characteristics of a binary phase Fresnel zone plate (FZP). The model shows that high Numerical-Aperture phase FZP under the illumination of linear polarized light produces rotationally asymmetric focal spot with beamwidth varying from 0.36λ to 0.79λ, where λ is the wavelength. On the other hand, rotationally symmetric focal spot with minimum beamwidth of 0.39λ can be obtained from the illumination of radial polarized light.
Yaoju Zhang - One of the best experts on this subject based on the ideXlab platform.
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diffraction theory of high Numerical Aperture subwavelength circular binary phase fresnel zone plate
Optics Express, 2014Co-Authors: Yaoju Zhang, Dong Zhang, Guihua Cui, Xiukai RuanAbstract:An analytical model of vector formalism is proposed to investigate the diffraction of high Numerical Aperture subwavelength circular binary phase Fresnel zone plate (FZP). In the proposed model, the scattering on the FZP’s surface, reflection and refraction within groove zones are considered and diffraction fields are calculated using the vector Rayleigh–Sommerfeld integral. The Numerical results obtained by the proposed phase thick FZP (TFZP) model show a good agreement with those obtained by the finite-difference time-domain (FDTD) method within the effective extent of etch depth. The optimal etch depths predicted by both methods are approximately equal. The analytical TFZP model is very useful for designing a phase and hybrid amplitude-phase FZP with high-NA and short focal length.
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effect of the shadowing in high Numerical Aperture binary phase fresnel zone plates
Optics Communications, 2014Co-Authors: Yaoju Zhang, Chongwei Zheng, Youyi ZhuangAbstract:Abstract Shadowing occurs for the groove zone plate when radiation origin from one zone of the zone plate must pass through another before reaching the focus point. Using the vector diffraction theory, we study the influence of the shadowing on the focusing properties of binary phase Fresnel zone plates (FZPs). The results show that a low-Numerical-Aperture (NA) FZP can be treated as an ideal in-plane FZP and the shadowing effect can be neglected. For a high-NA FZP, however, the shadowing effect from the etch depth has to be considered. Owing to the shadowing, the intensity of focusing spot decreases markedly and the size of focusing spot increases slightly in a high-NA FZP. The optimal etching depth of an actual FZP is smaller than that of an ideal FZP.
Xiukai Ruan - One of the best experts on this subject based on the ideXlab platform.
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diffraction theory of high Numerical Aperture subwavelength circular binary phase fresnel zone plate
Optics Express, 2014Co-Authors: Yaoju Zhang, Dong Zhang, Guihua Cui, Xiukai RuanAbstract:An analytical model of vector formalism is proposed to investigate the diffraction of high Numerical Aperture subwavelength circular binary phase Fresnel zone plate (FZP). In the proposed model, the scattering on the FZP’s surface, reflection and refraction within groove zones are considered and diffraction fields are calculated using the vector Rayleigh–Sommerfeld integral. The Numerical results obtained by the proposed phase thick FZP (TFZP) model show a good agreement with those obtained by the finite-difference time-domain (FDTD) method within the effective extent of etch depth. The optimal etch depths predicted by both methods are approximately equal. The analytical TFZP model is very useful for designing a phase and hybrid amplitude-phase FZP with high-NA and short focal length.
Rakesh G Mote - One of the best experts on this subject based on the ideXlab platform.
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subwavelength focusing behavior of high Numerical Aperture phase fresnel zone plates under various polarization states
Applied Physics Letters, 2009Co-Authors: Rakesh G Mote, S F Yu, Wei Zhou, Xiaofeng LiAbstract:An analytical model is developed to study the subwavelength focusing characteristics of a binary phase Fresnel zone plate (FZP). The model shows that high Numerical-Aperture phase FZP under the illumination of linear polarized light produces rotationally asymmetric focal spot with beamwidth varying from 0.36λ to 0.79λ, where λ is the wavelength. On the other hand, rotationally symmetric focal spot with minimum beamwidth of 0.39λ can be obtained from the illumination of radial polarized light.
Xiaosong Gan - One of the best experts on this subject based on the ideXlab platform.
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Focusing of doughnut laser beams by a high Numerical-Aperture objective in free space
Optics Express, 2003Co-Authors: Djenan Ganic, Xiaosong Gan, Min GuAbstract:We report on, in this letter, a phenomenon that the central zerointensity point of a doughnut beam, caused by phase singularity, disappears in the focus, when such a beam is focused by a high Numerical-Aperture objective in free space. In addition, the focal shape of the doughnut beam of a given topological charge exhibits the increased ring intensity in the direction orthogonal to the incident polarization state and an elongation in the polarization direction. These phenomena are caused by the effect of depolarization, associated with a high Numerical-Aperture objective, and become pronounced by the use of a central obstruction in the objective Aperture.
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splitting of the focal spot of a high Numerical Aperture objective in free space
Applied Physics Letters, 2002Co-Authors: James W M Chon, Xiaosong GanAbstract:Reported in this letter is a phenomenon that the focal spot of a high Numerical-Aperture objective in free space can split into two spots if a ring beam is used for illumination. Diffraction by a high Numerical-Aperture objective results in a depolarization such that the diffracted field in the focal region includes not only a component with the same polarization as the incident beam, but also orthogonal and longitudinal components. The use of a ring beam enhances the relative contribution from the longitudinal component. As a result, a single focal spot splits into two spots along the incident polarization direction. It is revealed theoretically that for an objective of given Numerical Aperture there is a threshold of the central obstruction size of a ring beam for the appearance of a two-peak focus.
