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双光子光折变介质中非相干耦合亮-暗屏蔽光伏孤子对 总被引:1,自引:1,他引:0
对有外加电场的双光子光伏光折变晶体中两束偏振方向和波长都相同的互不相干光束的耦合进行研究,给出产生亮-暗双光子光折变屏蔽光伏孤子对需满足的条件.以Cu:KNSBN晶体作为研究对象,选取α=117.3,β=83.79,η=1.5×10-4,σ=104,δ=0.005,r=10时,给出双光子光折变晶体中的非相干耦合亮-暗屏蔽光伏孤子对2个孤子分量光强的空间分布,证明有外加电场的双光子光伏光折变晶体中存在非相干耦合亮-暗屏蔽光伏孤子对,指出孤子对是由偏振态和波长都相同的两束互不相干光形成的,当外加电场方向和晶体中光伏电场的方向与晶体光轴方向相同时,双光子光折变晶体中可支持亮孤子峰值光强稍大于暗孤子最大光强的非相干耦合亮-暗孤子对,当外加电场方向和晶体中光伏电场的方向与晶体光轴方向相反时,双光子光折变晶体中可支持亮孤子峰值光强稍小于暗孤子最大光强的非相干耦合亮-暗孤子对. 相似文献
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根据光波耦合方程及亮-暗孤子对解,对稳态情况下多束互不相干的光束在有外加电场的双光子非光伏光折变晶体中的传播进行分析,给出产生亮-暗双光子光折变屏蔽光伏孤子族需满足的条件。证明有外加电场双光子非光伏光折变晶体中存在非相干耦合亮-暗混合屏蔽孤子族,孤子族由偏振态和波长都相同的多束互不相干的光形成。当外加电场方向和晶体光轴方向相同时,双光子光折变晶体可支持亮孤子族总峰值光强稍大于暗孤子族总峰值光强的的非相干耦合亮-暗混合孤子族,当外加电场方向与晶体光轴方向相反时,双光子光折变晶体可支持亮孤子族总峰值光强稍小于暗孤子族总峰值光强的非相干耦合亮-暗混合孤子族。 相似文献
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采用分步傅里叶法,数值模拟研究了有偏压光伏光折变晶体中艾里高斯光束的传输特性.结果表明,当艾里高斯光束初始振幅和晶体的外加电场在一定范围内时,可以形成沿直线稳定传输的呼吸式孤子.调节初始振幅或外加电场可以控制孤子的峰值强度和呼吸周期.随着入射光场分布因子的变大,孤子的平均峰值强度先增大后减小,孤子的呼吸周期先变小后变大.随着光束衰减因子的增加,孤子的平均峰值强度先增大后减小,然后再增大.此外,光束入射角为负值时,孤子向左偏移,光束入射角为正值时,孤子向右偏移.入射角只改变孤子的输出位置,不影响孤子的强度、宽度和呼吸周期. 相似文献
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(BaSr)TiO3晶体光诱导自泵浦位相共轭的实验研究 总被引:1,自引:1,他引:0
对(BaSr)TiO3晶体中光诱导自泵浦位相共轭现象进行了实验研究。发现诱导自泵浦的输出特性取决于诱导光束强度和信号光的入射条件,并在一定条件下呈现双稳性.作者认为,这是由于诱导光束改变晶体中信号光束Fanning散射强度分布的结果。 相似文献
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Based on the theory of paraxial electromagnetic beams in anisotropic medium, propagation properties of a linearly polarized confluent hypergeometric (HyG) beam through uniaxial crystals orthogonal to the optical axis are investigated. Analytical expressions are derived for the resultant optical field components. Effects of separate beam parameters together with the ratio of refractive indices of crystals on transversal intensity distributions are revealed by numerical calculations, respectively. It is shown that the beam profile finally converts into an elliptical shape due to influences of anisotropic crystals. Moreover, it is also indicated that through suitable selection of parameters, types of the optical vortices of resultant field would change from a central dark spot to a slight dark ring or an axial shadow during the propagation. These numerical results may provide alternative advantages to the trapping of tiny particles by utilizing HyG beams in practical experiments. 相似文献
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提出了一种基于非线性ZnSe晶体产生的空心光束与光泳力的大尺寸粒子二维囚禁与一维导引、三维囚禁方案.理论上分析并计算了单个非线性ZnSe晶体产生的空心光束内粒子受到的横向与纵向光泳力,纵向光泳力的大小同粒子尺寸与光束尺寸比例的四次方成正比,与空心光束功率成正比,方向与光束传播方向一致.粒子尺寸与空心光束尺寸越接近时,横向光泳力的大小越大.结果表明该光泳力可以实现对大尺寸粒子的二维囚禁,同时可对粒子进行长距离(米量级)一维定向导引;理论上分析并计算了基于双非线性ZnSe晶体产生的局域空心光束内粒子所受横向与纵向光泳力情况,光泳力与系统参数的依赖关系与单个非线性晶体产生的空心光束中的粒子受力情况类似,不同的是该条件下纵向光泳力指向光束中心.结果表明该局域空心光束可以实现大尺寸粒子的三维有效囚禁.基于非线性ZnSe晶体产生的空心光束或者局域空心光束可以作为大尺寸粒子非接触式有效操控的工具,在现代光学以及生物医学中有潜在的应用. 相似文献
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Jia Li Yanru Chen Shixue Xu Yongqing Wang Muchun Zhou Qi Zhao Yu Xin Feinan Chen 《Optics & Laser Technology》2011,43(3):506-514
The properties of Lorentz beams propagating in uniaxial crystals orthogonal to the optical axis are studied. The diffraction field components and effective beam sizes of the Lorentz beams are derived in analytical forms. Numerical results show that, upon propagating in uniaxial crystals, a Lorentz beam loses its initial Lorentz type distribution. Also, after propagating for sufficient distances, the transverse components would finally convert into a specific four-petal profile with an axial shadow, which may find applications in the optical trapping of particles. It also shows that the Lorentz beam parameters w0x, w0y and the ratios of refractive indices have strong influences on the diffraction field components and on the effective beam sizes when propagating in uniaxial crystals. 相似文献
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DING Zhihua LIU Yu BAO Zhengkang 《Chinese Journal of Lasers》2001,10(5):337-342
1 Introduction ThefirstworkwithopticaltrappingonsmallparticlesweredonebyAshkinetal.in1 985and 1 986 [1,2 ] ,Whosuccessfullydemonstratedthatmicroscopicparticlescouldbetrappedbyasinglefocussedlaserbeam .Anumberofdemonstrationsoftrappingandmanipulationofbiological… 相似文献
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从实验上研究了不同外加直流电场作用下固液同成分的SBN:Cr和SBN:Rh晶体的光致折射率变化规律.测量结果表明:无外加电场作用时,晶体中的光致折射率变化不明显;若在光辐照晶体的同时,沿晶体c轴方向施加一定方向的外电场,则晶体中即刻出现显著的光致折射率变化.这种折射率变化随外加电场的增大而增大,并且电场方向不同,折射率变化的正负也不同.因而可以通过改变外加电场的极性和幅度控制SBN:Cr和SBN:Rh晶体中光致折射率的变化特性,这对于在该类晶体中制作动态光波导具有重要意义. 相似文献
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A special kind of axicon prisms for beam transformation and enhancement of axial trapping force in a single-beam gradient optical trap is put forward. By inserting a pair of axicons into the parallel illumination path of a trapping objective, a center-weighted TEM00 Gaussian beam was transformed into an edge-weighted beam. Edge-weighted illumination for the trapping objective was thus realized, which is significant for the enhancement of axial trapping force. Based on a method of external sinusoidal excitation and lock-in detection, we precisely calibrated the axial spring constants of the same optical trap under different illumination conditions. The comparison results confirmed the feasibility of enhancing the axial trapping force by a pair of axicon. Moreover, the strength of enhancement was found to be dependent on the apodization factor for the input TEM00 Gaussian beam. 相似文献
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Liquid crystals (LC) are anisotropic materials which experience a torque if an electric field is present. This field can be due to an external voltage or to the presence of a light beam. Reorientation due to light leads to non-linear behavior in the optical behavior. Due to this kind of nonlinearity therefore it is possible to generate optical spatial soliton beam in LC by bias voltage or without it and interestingly chiral nematic liquid crystals has a opportunity to generate spatial optical solitons without the need for a bias voltage. In this paper we also demonstrate that a sharp switching of the helix structure occurs when the spatial soliton is launched in the middle of two regions where soliton generation is favorable. Due to the optical nonlinearity, the helical structure becomes asymmetric and a sharp switching in one direction can be obtained. Moreover, in this paper, the torque and reorientation of the liquid crystal and the change in angular momentum of the light are discussed. 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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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 下载免费PDF全文
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