共查询到20条相似文献,搜索用时 31 毫秒
1.
Based on the vector diffraction theory, the effect of phase modulation on the intensity distribution on tight focusing of cylindrically polarized Laguerre–Gaussian beam in the focal region of high NA lens is investigated theoretically. It is observed that a properly designed complex phase filter can generate multiple focal spot and focal hole segments useful for the manipulation of optical traps. 相似文献
2.
A binary phase grating capable of shaping an incident Gaussian beam to a flattop beam in a Fourier domain is designed iteratively. It is essential in grating design to consider the phases of diffracted waves by the grating, in addition to their amplitude uniformity and diffraction efficiency. The optimized grating phase produces the in-phase diffracted waves that interfere constructively to form a uniform amplitude and phase profile. The dependence of the shaped profile on the illuminating amplitude distribution, the grating misalignment, and the lens focusing error is investigated by computer simulation and optical experiment. 相似文献
3.
Thermoacoustic-reflected focusing lens based on acoustic Bessel-like beam with phase manipulation
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《中国物理 B》2018,(12)
We report the realization of broadband reflected acoustic focusing lenses based on thermoacoustic phased arrays of Bessel-like beams, in which the units of phase manipulation are composed of three rigid insulated boundaries and a thermal insulation film in air with different temperatures. Based on these units, we realize a reflected focusing lens which can focus reflected acoustic energy on a line, and its fractional bandwidth can reach about 0.29. In addition, we discuss the influences of the base angle of Bessel-like beam, the number of basic unit, and the variation of unit temperature on focusing performances in details. Furthermore, the reflected focusing lens for the cylindrical acoustic wave based on the Bessel-like beam is also demonstrated. The proposed focusing lens has the advantages of a broad working bandwidth, large focus size,and high robustness, which may provide possibilities for the design and application of acoustic lenses. 相似文献
4.
《Physics letters. A》2005,334(1):73-80
Taking into account the dispersion and the longitudinal chromatic aberration (LCA) of the material of the lens, focusing of isodiffracting pulsed Gaussian light beam through single lens is analyzed. The smaller the cycle number of the isodiffracting pulsed Gaussian light beam is, the higher the order of the material dispersion should be considered. 相似文献
5.
Yangjian Cai Q. Lin H. T. Eyyubo?lu Y. Baykal 《Applied physics. B, Lasers and optics》2009,94(2):319-325
The propagation of an elliptical Gaussian beam (EGB) through an astigmatic ABCD optical system in a turbulent atmosphere is
investigated. An analytical formula for the average intensity of an EGB and a generalized tensor ABCD law for the generalized
complex curvature tensor are derived. As an application example, we derived an analytical formula for the average intensity
of an elliptical flat-topped beam propagating through an astigmatic ABCD optical system in a turbulent atmosphere. As a numerical
example, the focusing properties of an EGB focused by a thin lens in a turbulent atmosphere are studied. It is found that
the focused beam at the focal plane becomes a circular Gaussian beam when the atmospheric turbulence is strong enough, and
the beam width of the circular Gaussian beam is determined by atmospheric turbulence strength, focal length of the thin lens,
and wavelength of the initial beam but is independent of the initial beam widths (i.e., initial intensity distribution). 相似文献
6.
1 Introduction Laserbeamswithamplitudemodulations(AMs)andphasefluctuations (PFs) proposedbytheLawrence LivermoreNationalLaboratory (LLNL)isatypicalphysicalmodelforhigh powerlasers[1] .Inhigh powerlasersystems,suchaslargeNd∶glasslaserfusiondrivers,high powerla… 相似文献
7.
Based on the treatment that a rectangular function can be expanded into an approximate sum of complex Gaussian functions with finite numbers, the analytical expression for the focusing intensity distribution of a laser beam with amplitude modulation (AM) and phase fluctuation (PF) through an aperture lens is derived. The typical numerical examples are given and compared with those obtained from numerically integral calculation. The results show that our method can significantly improve the numerical calculation efficiency. 相似文献
8.
Halil Tanyer Eyyubolu 《Optik》2007,118(6):289-295
For a Hermite hyperbolic/sinusoidal Gaussian beam with focusing properties, passing through an arbitrarily shaped rectangular aperture on the source plane and an on-axis x–y asymmetric ABCD system, the receiver plane expression is derived using the Collins integral. The specific example of a single thin lens placed on the propagation path is examined at selected source, propagation and optical element parameters. Viewing the progress of the beam in propagation, we find that subjecting the source beam to an aperture will give rise to excessive spreading during propagation. The lens setup will act to concentrate the energy of the beam around its focal point as expected, while in some circumstances it will also execute beam profile changes. By adjusting the aperture opening in the shape of a narrow slit, the beam will become aligned in the opposite direction after propagating after having traveled sufficiently. The results are presented as intensity graphs in the form of contour plots and 3D illustrations. 相似文献
9.
The ABCD law of parameter q for fundamental-mode Gaussian beam is deduced in this paper. The result shows that the changes of focal length and focal depth are not related to the orders of the Gaussian beam modes when focus lens moves along optical axis in a large range, indicating that the ABCD law of parameter q can be used for any order modes. A laser focusing setup is designed, and the response characteristics of oil pressure system therein are also studied. 相似文献
10.
《中国物理 B》2015,(4)
In this paper the propagation of elegant Hermite-cosh-Gaussian, elegant Laguerre Gaussian, and Bessel Gaussian beams through a Kerr left-handed metamaterial(LHM) slab have been studied. A split-step Fourier method is used to investigate the propagation of laser beams through this media. Numerical simulation shows that Gaussian beams have different focusing behaviors in a Kerr LHM slab with positive or negative nonlinearity. Beam focusing happens in slabs with positive nonlinearity and not in slabs with negative nonlinearity; however, negative nonlinearity is required for a Kerr LHM slab to act like a lens. Additionally, the focusing properties of beams can be controlled by controlling the thickness of the slab or the input power of the incident beam. A multilayer structure is also proposed to have beam focusing by thinner slabs and passing longer distances. 相似文献
11.
P. Chmela 《Czechoslovak Journal of Physics》1974,24(1):1-23
A process of generation of second harmonic frequency (S.H.G.) in focused light beam with the Gaussian distribution of light intensity is studied with the help of generalized diffraction theory in this work. Three methods of focusing are considered, namely, focusing with the spherical lens, focusing with the cylindrical lens in the plane of the principal cut and finally focusing with the cylindrical lens in the plane perpendicular to the plane of the principal cut. Two cases are discussed, namely, the case of S.H.G. in “diffractionless” light beam and the case of S.H.G. in strongly diffracted light beam. 相似文献
12.
Based on the generalized Huygens–Fresnel integral, analytical propagation formulas for a general-type beam propagating through aligned or misaligned ABCD optical systems in turbulent atmosphere are derived. The derived formulas provide a convenient way for studying the focusing properties of a variety of laser beams, such as Gaussian, cos-Gaussian, cosh-Gaussian, sine-Gaussian, sinh-Gaussian, flat-topped, Hermite-cosh-Gaussian, Hermite-sine-Gaussian, higher-order annular Gaussian, Hermite-sinh-Gaussian and Hermite-cos-Gaussian beams in turbulent atmosphere. As an application example, the focused intensities of cos-Gaussian, Hermite-sine-Gaussian and flat-topped beams in turbulent atmosphere are studied numerically. Focal shift of a flat-topped beam in turbulent atmosphere is investigated. Effect of the misalignment of the thin lens on the focusing properties of a cos-Gaussian beam is also explored. Our results will be useful for the applications of the general-type beam in LIDAR systems and remote sensing operating in turbulent atmosphere, where optical elements such as aligned or misaligned thin lens are commonly encountered. 相似文献
13.
S. G. Rautian 《Optics and Spectroscopy》2002,93(1):69-76
Propagation of a slightly diverging Gaussian beam in a gyrotropic medium [constitutive equation (1.1)] across the gyration vector g is considered. The polarization, phase, and geometrical features of the beams are elucidated. For a sufficiently small gyrotropy, the medium deflects the beams like a wedge while for a sufficiently large gyrotropy the medium focuses them like a cylindrical lens. For the field polarized along g, focusing automatically and completely eliminates the diffraction broadening of the beam along this direction. 相似文献
14.
Ultra-elongated depth of focus of plasmonic lenses with concentric elliptical slits under Gaussian beam illumination
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In this paper, we discuss the influence of ratio of minor to major axis on the propagation property and focusing performance of a plasmonic lens with variant periodic concentric elliptical slits illuminating under a Gaussian beam. In order to analyse the influence theoretically, a finite-difference time-domain (FDTD) numerical algorithm is adopted for the computational numerical calculation and the design of the plasmonic structure. The structure is flanked with penetrated slits through a 200-nm metal film (Au) which is coated on a quartz substrate. Tunability of focusing capability of the plasmonic lenses is studied by tailoring the ratio. Our calculation results demonstrate that the ratio of the elliptical slits greatly affects the focusing capability of the lense. The plasmonic lenses with concentric elliptical slits illuminating under a Gaussian beam have ultra-elongated depth of focus. These results are very encouraging for the future study of the plasmonic lens-based applications. 相似文献
15.
Tight Focusing Properties of Phase Modulated Radially Polarized Laguerre Bessel Gaussian Beam
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《中国物理快报》2017,(5)
We propose a new approach for generating a multiple focal spot segment of subwavelength size, by tight focusing of a phase modulated radially polarized Laguerre Bessel Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observe that the focal segment with multiple focal structures is separated with different axial distances and a super long dark channel can be generated by properly tuning the phase of the incident radially polarized Laguerre Bessel Gaussian beam. We presume that such multiple focal patterns and high intense beam may find applications in atom optics, optical manipulations and multiple optical trapping. 相似文献
16.
Focusing of elliptically polarized Gaussian beams through an annular high numerical aperture
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Based on the vectorial Debye theory,the focusing properties of the Gaussian beam through an annular high numerical aperture are studied numerically,including the intensity,the phase and the orbital angular momentum properties.Then the influence of certain parameters on the focusing properties is also investigated.It is shown that sub-wavelength elliptical light spots can be obtained.And there exists a vortex in the longitudinal component of the focused field even though the incident beam is Gaussian beam,indicating that the spin angular momentum of the elliptically polarized Gaussian beam is converted into the orbital angular momentum by the focusing. 相似文献
17.
The spatiotemporal and spectral characteristics of
ultrawide-band terahertz pulses after passing through a Fresnel lens
are studied by using the scalar diffraction theory. The simulation
shows that the transmitted terahertz waveforms compress with
increasing propagation distance, and the multi-frequency focusing
phenomenon at different focal points is observed. Additionally, the
distribution of terahertz fields in a plane perpendicular to the
axis is also discussed, and it is found that the diffraction not
only induces focusing on-axis but also inhibits focusing at off-axis
positions. Therefore, the Fresnel lens may be a useful alternative
approach to being a terahertz filter. Moreover, the terahertz pulses
travelling as a basic mode of a Gaussian beam are discussed in
detail. 相似文献
18.
19.
ABCD matrix formalism for propagation of Gaussian beam through left-handed material slab system 总被引:2,自引:0,他引:2
We apply a simple ABCD matrix formalism to investigate beam propagation in left-handed material (LHM) slab systems. Firstly, we derive the expressions for the matrix elements for a single LHM slab. Based on the ABCD matrix, we obtain the field distributions both inside and outside the LHM slab, and the conditions for focusing and phase compensation of the Gaussian beam. Secondly, the derived ABCD law is applied to analyze the propagation properties of Gaussian beams through various cascaded LHM slab systems. The corresponding focusing and phase compensation conditions of the Gaussian beam are also obtained. Our theoretic formalism may be applied as a compact and effective tool for the research of light beam propagation in complex LHM slab systems, since it avoids the complicated integral operation. 相似文献
20.
We propose a new approach for generating multiple focal spot segment of sub wavelength size, by tight focusing of phase modulated radially polarized Bessel Gaussian beam. The focusing properties are investigated theoretically by vector diffraction theory. We observed that focal segment with multiple focal spots structure separated with different axial distance can be generated by properly tuning the phase of the incident radially polarized Bessel Gaussian (BG) beam. Potential applications of this focal shaping technique are also discussed. 相似文献