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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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本文提出了产生自成像局域空心光束(self-imaged bottle beams)的一种光学元件------液体轴棱锥.从衍射理论结合几何光学对经过轴棱锥后的光场进行了分析, 得出注入液体折射率小于轴棱锥材料折射率时可产生自成像局域空心光束.并通过软件MathCAD模拟, 得到一个完整周期光束的变换过程和局域空心光束的演变过程.研究发现液体轴棱锥产生的自成像局域 空心光束具有周期及相干长度可调的特点.分析了如何利用自成像局域空心光束对粒子进行俘获, 讨论了用自成像局域空心光束进行多层面粒子俘获的优势. 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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Realization of a near-field optical virtual probe based on an evanescent Bessel beam is strongly dependent on a radially polarized
beam; this makes it essential to study the focusing property of the beam. In this paper, two experimental setups based on
a fiber device and a liquid crystal device, respectively, are built to generate a radially polarized beam. This beam and an
annular radially polarized beam are focused by means of a high numerical aperture objective and a solid immersion lens (SIL).
Near-field distribution of the focus spot, the evanescent Bessel field, is experimentally measured with a scanning near-field
optical microscope (SNOM). The full width at half maximum (FWHM) of the central peak of the evanescent Bessel field is about
200 nm in the close vicinity of the bottom surface of SIL. This has potential for use as a near-field optical virtual probe. 相似文献
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By use of a tensor method, an analytical formula for a partially coherent Gaussian Schell-model (GSM) beam truncated by a circular phase aperture propagating through a paraxial ABCD optical system is derived. The propagation properties of a GSM beam truncated by a circular phase aperture in free space are studied numerically. It is found that the circular phase aperture can be used to shape the beam profile of a GSM beam and generate partially coherent dark hollow or flat-topped beam, which is useful in many applications, e.g., optical trapping, free-space optical communication, and material thermal processing. The propagation factor of a GSM beam truncated by a circular phase aperture is also analyzed. 相似文献
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Multiple bottle beams based on metasurface optical field modulation and their capture of multiple atoms
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Xichun Zhang 《中国物理 B》2022,31(8):88103-088103
Compared to conventional devices, metasurfaces offer the advantages of being lightweight, with planarization and tuning flexibility. This provides a new way to integrate and miniaturize optical systems. In this paper, a metasurface capable of generating multiple bottle beams was designed. Based on the Pancharatnam-Berry (P-B) phase principle, the metasurface lens can accurately control the wavefront by adjusting the aspect ratio of the titanium dioxide nanopillars and the rotation angle. When irradiated by left-handed circularly polarized light with a wavelength of 632.8 nm, the optical system can produce multiple micron bottle beams. Taking two bottle beams as examples, the longitudinal full widths at half-maximum of the optical tweezers can reach 0.85 μ and 1.12 μ, respectively, and the transverse full widths at half-maximum can reach 0.46 μ and 0.6 μ. Also, the number of generated bottle beams can be varied by controlling the size of the annular obstacle. By changing the x-component of the unit rotation angle, the metasurface can also change the shape of the bottle beam — the beam cross-section can be changed from circular to elliptical. This paper also analyzes the trapping of ytterbium atoms by the multi bottle beam acting as optical tweezers. It is found that the multi bottle beam can cool and trap multiple ytterbium atoms. 相似文献
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We theoretically and experimentally investigate the Fraunhofer diffraction pattern of a vortex beam passing through an annular
ellipse aperture. It is found that the pattern of the far-field diffraction intensity distribution exhibits some dark spots,
which become clearer with increasing the value of the ellipticity factor of the annular ellipse aperture. The diffraction
phenomenon is more obvious with increasing the value of the ratio of the inner long axis (or short axis) to the outer side
of the annular ellipse aperture. The number of the dark spots in the Fraunhofer diffraction intensity distribution is just
equal to the topological charge value of the measured optical vortex, and the centre of each dark spot is just a phase-singularity
point. Based on this property, we can measure the topological charge of an optical vortex beam. 相似文献
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An annular phase-locking laser with annular gain media is presented. In this paper, the light field distribution of coherent annular beam (CAB) can be given by an analytical expression based on the Collins formula. Typical numerical examples are given to illustrate the application of our analytical result and the propagation property of a CAB through a paraxial ABCD optical system. 相似文献
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In recent years the partially coherent beams have attracted very much due to novel properties and its applications. In this paper the tight focusing properties of radially polarized partially coherent dark hollow beam (DHB) through a high numerical aperture lens are investigated numerically based on vectorial Debye theory in detail. The result shows that the optical intensity distribution in the focal region directly fluctuates due to small change in coherence length and high numerical aperture angle of the focused radially polarized partially coherent DHB. 相似文献
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The Fraunhofer diffraction pattern of a vortex beam by an annular triangle aperture is analyzed theoretically and experimentally. It is found that the pattern of the far-field diffraction intensity distribution exhibits a triangular lattice array, which becomes much clearer with the increase of the ratio of the inner to the outer side of the annular triangle aperture. The number of spot points of any external side of the triangular lattice array minus one is just equal to the topological charge value of the measured optical vortex. For the vortex beam with negative topological charge, the triangular diffraction pattern after the annular triangle aperture will be rotated by 180° in relation to the case of the positive topological charge. Based on the above properties, we propose a simple and feasible method to determine the magnitude and sign of the topological charge of an optical vortex beam. 相似文献
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在部份相干光照明下的环型孔成像系统,对两个点物之分辨,按照Sparrow判据作了分析和研究,将两点之分辨作为两个参数的函数进行讨论-其一为照明光的空间相干条件,其二为环型孔的中心阻挡,在与圆型孔和完全相干照明的情况比较之后指出,环型孔和部份相干照明情况具有更高的两个点物的分辨本领。 相似文献
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By expanding a hard aperture function into a finite sum of complex Gaussian functions, approximate propagation formula is derived in the situation that the beam generated by Gaussian mirror resonator passes through a paraxial ABCD optical system with an annular aperture. The corresponding forms for a circular aperture and a circular black screen are also given. Some numerical simulations are shown to illustrate propagation properties and focusing properties of the beam passing through a paraxial ABCD optical system with the three different kinds of aperture. 相似文献
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Focal shift of hyperbolic-cosine-Gaussian beams induced by pure phase apodizer was investigated theoretically. The pure phase apodizer consists of three concentric zones: center circle zone, inner annular zone and outer annular zone. And the phase variance of the inner annular zone is adjustable. Results show that intensity peak moves far from optical aperture and then shrinks sharply for certain radii of zones with increasing phase variance of the inner annular zone. Simultaneously, one new intensity peak occurs near optical aperture, moves far from the optical aperture, and then becomes intensity maximum peak, and repeats the evolution process of the former intensity peak. Tunable focal shift occurs with focal switch. Decreasing the phase variance can change the move direction of the intensity peaks. In addition, the maximum distance between the two intensity peaks can be altered by beam parameters of cosh parts, and the distance value increases and then decreases with increasing beam parameters of cosh parts for certain radii of zones. Tunable focal shift is also discussed to construct optical tweezers. 相似文献
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The rich available transverse intensity structure of vector Bessel-Gauss beams make it important to probe into the focusing property by high numerical aperture objective. In this paper, we obtain the analytical expressions of azimuthally, radially and longitudinally polarized components in the focal area of the objective after tight focusing. Theoretical analysis and the numerical simulation show that, the transverse intensity distributions of the focused beams still have doughnut-like structure, two separate peak structure and circularly aligned array structure. The focused beam spots obtained by an objective with annular aperture usually have smaller spots than with circular aperture. The focused beam of the vector Bessel-Gauss beam with lowest mode number m = 0 is a radially and azimuthally polarized doughnut-like beam with no longitudinal component. These properties and results are useful in optical trapping and particle alignment. 相似文献
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Y. Poujet M. Roussey J. Salvi F.I. Baida D. Van Labeke A. Perentes C. Santschi P. Hoffmann 《Photonics and Nanostructures》2006,4(1):47-53
This paper presents experimental studies of the enhanced light transmission through metallic films pierced by subwavelength annular apertures. Two different methods (e-beam lithography and focused ion beam) have been used to build the nano-structures. We have experimentally recorded their far-field spectral response in the visible range and the optical near-field above the nano-structures when they are excited at 633 nm. The spectral response exhibits a transmission peak at 700 nm with maximum efficiency around 16%. The near-field exhibits a characteristic two-lobe structure just above the aperture. Finite difference time domain (FDTD) simulations reproduce quite well the experimental results. 相似文献