共查询到18条相似文献,搜索用时 359 毫秒
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非均匀手征分层粒子的俘获特性研究在化学工程、生物医药、光镊、微纳米加工等领域都有着重要的应用.为了有效地俘获及操控手征分层球形粒子,本文对椭圆高斯波束照射下手征分层球形粒子的辐射俘获力展开研究.从广义米理论出发,将入射椭圆高斯波束用矢量球谐函数展开,根据波束散射理论及电磁场动量守恒定理,得出椭圆高斯波束对手征分层球形粒子辐射俘获力的级数表达式,并对椭圆高斯波束入射分层手征细胞时的轴向及横向俘获力进行了数值模拟,讨论了手征参数、极化状态、束腰宽度、损耗以及最外层厚度对俘获情况的影响.研究表明:手征参数的引入会降低非均匀手征粒子的轴向俘获特性,但是选择合适的极化态入射时,可以有效地实现对非均匀手征粒子的稳定俘获.对于内层损耗小的手征多层球形粒子,当内层折射率大于最外层时,最外层厚度大的非均匀手征粒子在光轴上更容易俘获;反之内层折射率小于最外层时,最外层厚度小的粒子在光轴上有更强的束缚;同时与传统圆高斯波束相比,椭圆高斯波束的强会聚性更容易实现对非均匀手征分层细胞的三维俘获,具有良好的应用前景. 相似文献
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基于广义洛仑兹-米氏理论(GLMT),研究了高斯波束对离心球的纵向辐射俘获力.用积分区域近似法计算波束系数,散射场的展开系数由矢量球面波函数的加法定理并求解边界条件得到.给出了高斯波束对在轴离心球辐射俘获力的计算公式并进行了数值模拟.将离心球退化为同心双层球,对离心球辐射俘获力的公式进行了验证.讨论了离心距对纵向俘获力的影响,也讨论r束腰半径、介质折射率和波长对纵向辐射俘获力的影响. 相似文献
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为了研究吸收双层球形微粒的横向光俘获,基于几何光学模型提出了双层带吸收球形微粒的光俘获模型,对TEM00模式高斯光束照射下外层有光吸收的双层电介质球形微粒受到的横向光俘获力进行了数值模拟,取得了光俘获力特性的一系列结果.结果显示,双层球形微粒的外层吸收系数对包括稳态俘获位置,峰值强度,稳态俘获的刚度等光俘获特性有很大影响.此外,内外径的比率对吸收双层球形微粒的光俘获特性也有调制性的影响.在一定条件下,带吸收的双层球形微粒可以被俘获在光轴上,也可能被俘获在中心在光轴上的圆环上.
关键词:
光俘获
几何光学模型
高斯光束
吸收双层球 相似文献
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离轴多层球对高斯波束的光散射 总被引:2,自引:2,他引:0
根据广义米氏理论,将入射的高斯波束按矢量球谐函数展开,获得了波束因子(展开系数)gmn,TM和gmn,TE的一般表达式。应用gmn的局域近结果和散射系数anm和bnm的迭代公式与算法,研究了多层有耗介质球的光散射。讨论了波束宽度与球形粒子的尺寸和位置对散射系数和散射强度角分布的影响。 相似文献
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从声波的散射理论出发,利用级数展开法得到高斯波束的波束因子,推导其对阻抗边界下离轴球形粒子声辐射力.针对刚性球与液体球两种球形粒子进行数值模拟,与自由空间的情况进行比较.讨论边界反射系数、粒子与边界距离、束腰半径以及离轴角度与距离等对声辐射力的影响.仿真结果表明:边界反射系数的增大会引起声辐射力的增加,但不改变峰值的位置;在合适的频率处,可以产生负向声辐射力;声辐射力随粒子与边界距离呈周期性变化;束腰半径的影响主要体现在中高频;随着粒子偏离传播轴的距离和角度增大,声辐射力明显衰减.该研究为利用高斯波束实现对粒子的操纵提供理论基础. 相似文献
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本文采用三维时域有限差分法(FDTD)和Maxwell应力张量法建立了单光镊在焦点附近俘获球形微粒的光阱力模型,采用基于球矢量波函数(VSWF)的五阶高斯光源作为仿真光源,得到了准确的光场传播.讨论了光源的波长、束腰、偏振态和微球的半径、折射率对光阱力的影响,分析了在单光镊俘获微球时,邻近微球对光阱力的影响.特别研究了光源的偏振态对微球所受光阱力的作用效果,仿真结果表明圆偏振光比线偏振光对微球的俘获力更大;被光镊稳定俘获的微球,会受到邻近微球干扰,失去平衡状态,改变光源的偏振态可以改变微球的受力状态.
关键词:
光镊
光阱力
介质微球
时域有限差分法(FDTD) 相似文献
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Generalized Lorenz-Mie theory and applications 总被引:1,自引:0,他引:1
James A. Lock Gérard Gouesbet 《Journal of Quantitative Spectroscopy & Radiative Transfer》2009,110(11):800-6656
The basic formulas of generalized Lorenz-Mie theory are presented, and are applied to scattering of a focused Gaussian laser beam by a spherical particle. Various applications of focused beam scattering are also described, such as optimizing the rate at which morphology-dependent resonances are excited, laser trapping, particle manipulation, and the analysis of optical particle sizing instruments. Each of these applications requires either special positioning the beam with respect to the particle or illumination of only part of the particle by the beam. 相似文献
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Systematical study of the trapping forces of optical tweezers formed by different types of optical ring beams 总被引:2,自引:0,他引:2
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The technique of optical tweezers has been improved a lot since its
invention, which extends the application fields of optical tweezers. Besides
the conventionally used Gaussian beams, different types of ring beams have also been
used to form optical tweezers for different purposes. The two typical
kinds of ring beams used in optical tweezers are the hollow Gaussian beam and
Laguerre--Gaussian (LG) beam. Both theoretical computation and experiments
have shown that the axial trapping force is improved for the ring beams
compared with the Gaussian beam, and hence the trapping stability is
improved, although the transverse trapping forces of ring beams are smaller
than that of Gaussian beam. However, no systematic study on the trapping
forces of ring beam has ever been discussed. In this article, we will investigate
the axial and transverse trapping forces of different types of ring beams
with different parameters systematically, by numerical computation in which
the ray optics model is adopted. The spherical aberration caused by the
refractive index mismatch between oil and water is also considered in the
article. The trapping forces for different objectives that obey the sine
condition and tangent condition are also compared with each other.
The result of systematical calculation will be useful for the applications
of optical tweezers formed by different types of ring beams. 相似文献
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Calculation and optical measurement of laser trapping forces on non-spherical particles 总被引:1,自引:0,他引:1
T. A. Nieminen H. Rubinsztein-Dunlop N. R. Heckenberg 《Journal of Quantitative Spectroscopy & Radiative Transfer》2001,70(4-6):627-637
Optical trapping, where microscopic particles are trapped and manipulated by light is a powerful and widespread technique, with the single-beam gradient trap (also known as optical tweezers) in use for a large number of biological and other applications. The forces and torques acting on a trapped particle result from the transfer of momentum and angular momentum from the trapping beam to the particle. Despite the apparent simplicity of a laser trap, with a single particle in a single beam, exact calculation of the optical forces and torques acting on particles is difficult. Calculations can be performed using approximate methods, but are only applicable within their ranges of validity, such as for particles much larger than, or much smaller than, the trapping wavelength, and for spherical isotropic particles. This leaves unfortunate gaps, since wavelength-scale particles are of great practical interest because they are readily and strongly trapped and are used to probe interesting microscopic and macroscopic phenomena, and non-spherical or anisotropic particles, biological, crystalline, or other, due to their frequent occurance in nature, and the possibility of rotating such objects or controlling or sensing their orientation. The systematic application of electromagnetic scattering theory can provide a general theory of laser trapping, and render results missing from existing theory. We present here calculations of force and torque on a trapped particle obtained from this theory and discuss the possible applications, including the optical measurement of the force and torque. 相似文献
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The wavelength-dependent intensity of a light beam scattered by an isotropic homogeneous particle illuminated with an on-axis monochromatic polarized Gaussian beam is calculated in this paper. The vector spherical harmonics expansion and T transformation matrix are used to form the theoretical basis. Numerical results show that the angular intensity distribution is symmetric for an on-axis polarized Gaussian beam illumination upon an aqueous spherical particle at 473, 532 and 660 nm. For the specified aqueous spherical particle, the scattered intensity distribution decreases with increase in wavelengths. 相似文献
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Huayong Zhang 《Journal of Quantitative Spectroscopy & Radiative Transfer》2011,112(9):1486-1491
A generalized Lorenz-Mie theory framework (GLMT) is applied to the study of Gaussian beam scattering by a spherical particle with an embedded spheroid at the center. By virtue of a transformation between the spherical and spheroidal vector wave functions, a theoretical procedure is developed to deal with the boundary conditions. Numerical results of the normalized differential scattering cross section are presented. 相似文献
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Based on spherical vector wave functions and their coordinate rotation theory,the field of a Gaussian beam in terms of the spherical vector wave functions in an arbitrary unparallel Cartesian coordinate system is expanded.The beam shape coefficient and its convergence property are discussed in detail.Scattering of an arbitrary direction Gaussian beam by multiple homogeneous isotropic spheres is investigated.The effects of beam waist width,sphere separation distance,sphere number,beam centre positioning,and incident angle for a Gaussian beam with two polarization modes incident on various shaped sphere clusters are numerically studied.Moreover,the scattering characteristics of two kinds of shaped red blood cells illuminated by an arbitrary direction incident Gaussian beam with two polarization modes are investigated.Our results are expected to provide useful insights into particle sizing and the measurement of the scattering characteristics of blood corpuscle particles with laser diagnostic techniques. 相似文献