共查询到20条相似文献,搜索用时 31 毫秒
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Refraction of a cylindrical laser beam in a transition layer at the interface of two liquids with different optical characteristics is studied theoretically and experimentally. A theoretical basis for calculations of the beam trajectory in the transition layer of stratified liquid is given. Two- and three-dimensional images (2D and 3D refractograms) of a cylindrical laser beam inside and outside the media are obtained on the basis of a tangential model of the refractive index profile. The influence of the parameters of the laser beam and media on the appearance of refractograms is studied and the optimal experimental conditions are selected with the use of computer simulation. A scheme of the setup for recording digital 2D refractogram and experimental results are presented. Algorithms for digitizing experimental images and for their comparison with calculated refractograms to determine the refractive index profile in the transition layer based on the tangential model are developed. 相似文献
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D.W. Mueller Jr. A.L. Crosbie 《Journal of Quantitative Spectroscopy & Radiative Transfer》2006,98(3):330-357
The focus of this two-dimensional study is the radially varying intensity emergent from a plane-parallel scattering medium exposed to a collimated, Gaussian laser beam directed perpendicular to the upper surface. The method of analysis is the integral transform technique. Specifically, this work uses the generalized reflection and transmission functions from a previous study to construct the emergent intensity with the use of an inverse Hankel transform. Radially varying backscattered and transmitted intensities are calculated for media with isotropic and Rayleigh scattering phase functions and optical thicknesses that range from 0.125 to 8.0. The behavior of the emergent radiation inside and outside the beam is investigated for both narrow and wide beams. A new integration method is implemented to compute the emergent intensity at the beam center. The emergent intensity at the beam center is used to quantify when a one-dimensional model may be used. As expected, for small optical thicknesses and near the beam the phase function has significant influence, while far from the beam multiple scattering reduces the influence of the Rayleigh phase function. Results from this study will be useful in understanding and interpreting more complicated situations, such as those that include polarization. 相似文献
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为了研究大气湍流对高斯涡旋光束传递信息的影响,理论分析了经过大气湍流的高斯涡旋光束轨道角动量(OAM)模式的径向平均功率和归一化平均功率分布、固有模式指数、初始光束半径和湍流强度;采用纯相位扰动逼近的有效性,数值模拟高斯涡旋光束在传输中的OAM模式径向平均功率分布的变化。建立传输模型并进行外场激光大气传输实验,对比分析了模拟和实测的OAM归一化平均功率分布,结果表明在弱湍流条件下,OAM模式的径向平均功率随着接收器孔径尺寸的增加而变化,逐渐趋于稳定值。对于一般常用的接收孔径,在强湍流或较小的初始光束半径条件下对OAM模式干扰十分严重。验证了用数值方法模拟OAM在湍流介质中的模式变化过程的可靠性。 相似文献
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We have presented an investigation of the induced focusing in Kerr media of two laser beams, the pump beam and the probe beam,
which could be either Gaussian or elliptic Gaussian or a combination of the two. We have used variational formalism to derive
relevant beam-width equations. Among several important findings, the finding that a very week probe beam can be guided and
focused when power of both beams are well below their individual threshold for self-focusing, is a noteworthy one. It has
been found that induced focusing is not possible for laser beams of any wavelength and beam radius. In case both beams are
elliptic Gaussian, we have shown that when power of both beams is above a certain threshold value then the effective radius
of both beams collapses and collapse distance depends on power. Moreover, it has been found that induced focusing can be employed
to convert a circular Gaussian beam into an elliptic Gaussian beam. 相似文献
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Zhongke Wang Koji Sugioka Katsumi Midorikawa 《Applied Physics A: Materials Science & Processing》2007,89(4):951-955
We report the three-dimensional (3D) integration of microoptical components such as microlenses, micromirrors and optical
waveguides in a single glass chip by femtosecond (fs) laser direct writing. First, two types of microoptical lenses were fabricated
inside photosensitive Foturan glass by forming hollow microstructures using fs laser direct writing followed by thermal treatment,
successive wet etching and additional annealing. One type of lens is the cylindrical microlens with a curvature radius R of
1.0 mm, and the other is the plano-convex microlens with radius R of 0.75 mm. Subsequently, by the continuous procedure of
hollow microstructure fabrication, a micromirror was integrated with the plano-convex microlens in the single glass chip.
Further integration of waveguides was performed by internal refractive index modification using fs laser direct writing after
the hollow structure fabrication of the microlens and the micromirror. A demonstration of the laser beam transmission in the
integrated optical microdevice shows that the 3D integration of waveguides with a micromirror and a microoptical lens in a
single glass chip is highly effective for light beam guiding and focusing.
PACS 42.62.-b; 81.05.Kf; 42.82.Cr; 82.50.Pt; 42.79.Gn 相似文献
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Investigation of Near-Field Imaging Characteristics of Radial Polarization for Application to Optical Data Storage 总被引:4,自引:0,他引:4
Wan-Chin Kim No-Cheol Park Yong-Joong Yoon Hyun Choi Young-Pil Park 《Optical Review》2007,14(4):236-242
Radially polarized incident light can generate a more confined longitudinal electric field on a focal plane in near-field
(NF) optics than focusing circularly polarized light. Using this phenomenon, it is feasible to reduce beam spot size on storage
media to increase the areal density of optical data storage. A radially polarized beam generates a beam spot which is 20%
more confined on the 1st surface of medium than that of circularly polarized light. However, the peak intensity of total electric
field sharply decreases and its transverse component is much more dominant inside the media stack. This confirms that radially
polarized optics can be a candidate not for an NF recording system but for an NF read-only memory (ROM) system. Potentially,
the results could be useful to understand the effect of radial and circular polarizations inside and outside medium for various
applications of NF optics. 相似文献
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We introduce a novel method to generate the optical vortex with computer-generated hologram (CGH) fabricated inside glass by femtosecond laser pulses. The CGH was directly written inside glass by femtosecond laser pulses induced microexplosion without any pre- or post-treatment of the material. We also realized the restructured optical vortex beams of both the transmission and reflection pattern with high fidelity using a collimated He-Ne laser beam. The total diffractive efficiency of both the transmission and reflection pattern is about 4.79%. 相似文献
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An optical communication scheme of 2-D pattern transfer based on imaging optics for submarine laser uplink communication (SLUC) is suggested. Unlike the methods aiming at avoiding neighboring crosstalk used in traditional multi-channel optical beam transferring, we make full use of the overlapping of each spreading beam other than controlling divergence effect of each beam to avoid interference noise. The apparent parameters have been introduced to simplify theoretical analysis of optical pattern transfer problem involving underwater condition, with the help of which the complex beam propagation inside two kinds of mediums can be easily reduced to brief beam transfer only inside air medium. In this paper, optical transmission path and receiver terminal optics geometry have been described in detail. The link range equation and system uplink performance analysis have also been given. At last, results of a proof-of-concept experiment indicate good feasibility of the proposed SLUC model. 相似文献
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The steady state nonlinear propagation of an intense, circularly polarized electromagnetic beam in an inhomogeneous magnetized plasma has been investigated in paraxial approximation. The laser induces a large oscillatory velocity on electrons, raising their mass and lowering the plasma frequency. Further, rising due to cyclotron resonance effect. The propagation of the electromagnetic waves in magnetized plasma in both the extraordinary and ordinary mode is analyzed. The nonlinearity in dielectric function is considered in presence of external magnetic field due to saturation effects for arbitrary large intensity, which leads to focusing/defocusing of the beam. The focusing effect along with magnetic field helps in the process of anomalous penetration of the beam by enhancing the depletion of the plasma from the axial region. The penetration increases with the incident beam power up to some critical value beyond which it rises abruptly when all electrons have been driven out of the axis. The cyclotron resonance effect awfully supports the laser beam to propagate inside the overdense plasma region. Numerical computations are performed for typical parameters of relativistic laser–plasma interaction applicable for underdense and overdense plasma. 相似文献
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Ismail Rafatov 《Physics letters. A》2009,373(37):3336-3341
We studied the effect of the laser beam focusing geometry on the continuous optical discharge (COD) properties. We used a full two-dimensional radiative gas-dynamic model for the COD, maintained by a vertical CO2 laser beam in free air atmosphere, in the Earth's gravitational field. The model takes into account all of the factors that are of importance in laser-sustained plasma processes, and uses realistic quasi optics to describe the laser radiation propagation. Results are presented for the optical discharge parameters as functions of applied laser power and degree (f-number) to which the laser beam is focused. 相似文献
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高功率激光光束特性对激光加工的影响 总被引:4,自引:0,他引:4
决定光与物质相互作用的激光束的波长、入射角、偏振特性以及时间和空间特性是激光材料加工的主要光束特性。激光束的光束质量是其空间特性的量化反映。通过对两种不同激光加工系统输出激光光束质量进行测量和计算,根据多模激光束的聚焦理论,以及对激光深熔焊接实验结果的分析,研究了光束质量对深熔焊接焊缝成形的影响。结果表明,光束质量对聚焦光束的焦斑、聚焦角和焦深的影响不仅体现了激光源的可聚焦性,而且也标志了激光源的可加工能力,这是聚焦系统和焦点位置在选择过程中应该考虑的重要因素。 相似文献
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Pavel Polynkin 《Applied Physics A: Materials Science & Processing》2014,114(1):143-149
We review recent results on the propagation and self-focusing of intense femtosecond laser pulses with shaped beam profiles in transparent dielectric media. At sufficiently high optical power, beam shaping seeds into the transverse modulation instability and results in the deterministic placement of intense laser filaments within the beam profile. Resulting spatial filament distributions may be utilized for writing complex extended structures inside transparent dielectrics. Specific examples of beam shapes we will discuss are Bessel beams, optical vortices, Bessel beams of higher order, and Airy beams. 相似文献
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M. Ghorbanalilu 《Optics Communications》2012,285(5):669-672
The spot-size evolution of circularly polarized intense laser beam propagating through the axially magnetized electron–positron (EP) and electron plasmas is discussed, in mildly relativistic and weakly non-linear (a2 ? 1) regime. The non-linear current density source terms are obtained by making used of the perturbative technique. The variational principle approach method is applied to the solution of the non-linear Schrodinger wave equation. It is shown that the laser beam spot size decreases for the left and increases for the right handed polarized beams with increasing the external magnetic field, owing to the beam passages inside the electron plasma. Furthermore, it is revealed that the self focusing property strongly enhanced in the EP plasma in comparison to the electron plasma. Moreover, self focusing of linearly polarized laser beam is investigated for EP plasma by superposition of the right and left circularly polarized beams. 相似文献