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应用傅里叶频谱分析法,给出了光栅在啁啾超短脉冲光波照射下菲涅耳衍射方程并分析了其Talbot效应. 数值计算表明,在Talbot距离处的衍射光强不仅与照射的超短脉冲光波的宽度有关,而且与脉冲光波的啁啾有关. 根据光栅在Talbot距离处衍射光强的变化,给出了一种检验超短脉冲光波是否含有啁啾的简单方法.
关键词:
光栅
菲涅耳衍射
Talbot效应
啁啾超短脉冲激光 相似文献
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本文提出了用液晶空间光调制器制作复合相位光栅、产生三维光阱阵列的新方案.在本方案中,首先将一维矩形光栅转变为能够产生纵向光阱阵列的环形光栅,再把环形光栅和二维矩形光栅组合成复合光栅.根据现有空间光调制器的技术参数,模拟仿真设计了产生5×5×5光阱阵列的光栅,以普通功率的高斯光波为输入光,正透镜聚焦衍射光,计算输出光强分布,结果表明:在透镜焦点附近获得具有很高峰值光强和光强梯度的三维光阱阵列,囚禁冷原子的光学偶极势达到mK量级,对原子的作用力远大于原子的重力.用大功率激光作为输入光波时,产生的光阱阵列也能用于囚禁Stark减速后的冷分子. 相似文献
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为了直观描述光栅中电磁场复杂的空间分布,利用Comsol多物理场软件进行严格耦合波分析,对周期性微纳米光栅结构进行建模,生动清晰地呈现出光栅衍射的光强分布并计算其透反射率.通过改变光栅常数、入射波长参数得出相应衍射图样、强度分布及透射率,利用衍射率最佳的参数进一步分析金属银光栅对光栅衍射强度分布的影响,得到了基于表面等离子体激元(surface plasmon polartions, SPPs)增强的衍射效应;通过改变银栅高度得到波导光栅,光栅缝隙之间呈现出周期性场增强现象,并对其基于光波导耦合效应做出解释,为衍射光栅的优化设计和应用提供了理论指导. 相似文献
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为研究局域体光栅的光折变形成机制及衍射特性,以双中心非挥发全息记录方案为基础,将带输运模型与二维耦合波理论相结合,采用数值模拟的方法.研究紫外敏化光强和记录红光总光强的变化对LiNbO3:Fe:Mn晶体中局域体光栅的影响,并给出定影结束时平均折射率调制、衍射光波振幅及衍射效率的模拟结果.研究发现:记录红光总光强不变时,平均折射率调制随紫外敏化光强增加而增加,而紫外敏化光强的改变对衍射波振幅的分布影响不大,衍射效率随紫外敏化光强度的增大先增大后减小,存在最佳紫外敏化光强,以获得80%以上的最高衍射效率.当紫外敏化光强不变时,随着记录红光总光强的增加,记录折射率光栅逐渐减弱,衍射波振幅分布变得越来越均匀.衍射效率逐渐降低. 相似文献
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A. A. Ionin S. I. Kudryashov L. V. Seleznev D. V. Sinitsyn V. I. Emel’yanov 《JETP Letters》2013,97(3):121-125
A surface electromagnetic wave has been excited on an atomically smooth silicon surface by an intense infrared femtosecond laser pulse as a result of its self-diffraction on a microscale short-lived optical inhomogeneity of the excitation region rather than on the roughness of its surface relief. This wave has been visualized in the form of the pattern of its interference with the same incident infrared ultrashort pulse, which corresponds to the instantaneous surface dielectric constant grating (reflection), as well as the resulting surface relief grating, using time-resolved far-field optical reflection microscopy. 相似文献
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The time evolution of photoinduced surface relief grating formation on azobenzene polymer films is analyzed by particle method for fluid mechanics. The surface relief grating is grown by using two beams interference with various polarization states numerically and compared with experimental results. The force acted on the dipole by electromagnetic field and surface force are considered as the driving force for photoinduced mass transport. The improved surface tension model is proposed in order to calculate curvature coefficient. The numerical results are coincided with experimental results qualititatively. 相似文献
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Bastonero Sergio Lancellotti Vito Orta Renato 《Optical and Quantum Electronics》1999,31(9-10):943-955
A modal method for the analysis of surface relief gratings made with anisotropic material is presented. The structure is decomposed into a series of cascaded discontinuities between planar waveguides with stratified anisotropic dielectric. The basic problem is formulated by an integral equation which is solved numerically by the method of moments. The mode functions of the periodic region are assumed as basis functions to represent the unknown field on the junctions. Each junction is viewed as a waveguide junction problem and has been characterized by the generalized scattering matrix (GSM). The diffraction efficiencies of the grating are determined by combining the various GSM. In this way, the analysis method is stable and can be applied also to deep gratings. 相似文献
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G. F. Glinskii 《Russian Physics Journal》1980,23(4):318-321
The metrical properties of four-space in the presence of a nonlinear electromagnetic field in vacuum are investigated. It is shown that the metric induced by the nonlinear electromagnetic field has a complicated nature and corresponds to an anisotropic space-time, i.e., to a four-space in which birefringence is observed. A special case of such a space is ordinary Riemann-Euclid space. As an example, the influence on the metric of the radiative corrections that follow from quantum electrodynamics is considered.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 4, pp. 52–55, April, 1980. 相似文献
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Bastonero S. Peverini O.A. Orta R. Tascone R. 《Optical and Quantum Electronics》2000,32(6-8):1013-1025
A modal method is used for the analysis under oblique incidence of a diffraction grating made of anisotropic material. The problem is studied viewing the structure as the cascade of junctions between periodic arrays of anisotropic slab waveguides with the same period and different heights. This diffraction problem is formulated in terms of an integral equation that enforces the continuity of the transverse magnetic field at the junction. The unknown is the transverse electric field at the junction. It is possible to use also another formulation, where the role of the two fields is exchanged. The kernels of these equations are the relevant Green's functions, which are expressed in terms of eigenfunction expansions. The determination of the modes of the various regions composed of arrays of anisotropic dielectric slabs has been carried out by the method of spectral elements, whereby the field components are represented in a polynomial basis and the original differential eigenvalue problem is converted into an algebraic one. The integral equation is solved numerically by the method of moments and each junction is characterized by its generalized scattering matrix (GSM). Finally, the diffraction efficiencies of the grating are obtained by combining the various GSM's. 相似文献
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将矢量衍射数值算法—严格耦合波分析用于精确计算亚波长闪耀光栅的衍射效率,并分析其衍射特性。建立了闪耀光栅的电磁介质模型,并将楔形不规则结构简化为多层矩形光栅结构,通过电磁场的介质分布建立严格耦合波方程。根据边界条件求解出各层的电磁场分布,再通过增透矩阵方法将各层电磁场依次迭代,求解出了整个结构的衍射效率。计算分析显示,对闪耀角为11.3°、周期为500 nm的金属铝闪耀光栅可以得到高于90%的衍射效率和相应的闪耀级次。实验表明这种矢量衍射数值算法具有较高的准确性,可以推广应用于高致密刻线复杂光栅的衍射计算分析。 相似文献
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Shakeel Ahmed 《Optics Communications》2008,281(17):4211-4218
Electromagnetic scattering of an incident plane wave from a rectangular strip and strip grating, are presented semi-analytically. The strip and strip grating are simulated by joining parallel perfect electromagnetic conductor (PEMC) circular cylinders and are illuminated by a TMz incident plane wave. The PEMC medium does not allow electromagnetic energy to enter. An interface of this medium serves as an ideal boundary to the electromagnetic field. The solution is based on the application of the boundary conditions on the surface of each cylinder in terms of its local coordinate system. The technique is used to predict the scattered field pattern of PEMC strip and PEMC strip grating. 相似文献
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为了分析窄带电磁脉冲源近、远场辐照大型建筑物内部空间电磁场分布特点,采用时域有限差分方法,对比分析平面波、球面波场源正面斜入射多层多单元建筑物的计算结果,并较为全面地分析了各房间各水平面中心电场强度幅值、各层各水平面电场强度最大值分布情况。建筑物各层相对应高度面上场强分布近似,在电磁波传播方向上窗户房间内部区域场强较强,两种波场源入射结果基本一致;在其余区域场强较弱,特别是在较大空间内的区域,球面波场源入射下场强相对更弱。其中通过与待模拟建筑物外形相紧凑性匹配的球面波场源构建,模拟仿真了窄带球面电磁波在真空空间的辐射传播,计算结果验证所构建球面波近场源准确可行。 相似文献
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Talbot效应是一种近场自成像效应,通常只有周期光栅可以产生Talbot效应,而环形光栅无法产生.本文通过引入保角变换,发现可以在环形光栅外部设计适当的折射率渐变层介质,使得其中也能够产生严格的Talbot效应,并计算了对应的自成像半径表达式.本文利用FDTD软件分别将一个环形光栅放置在真空中以及人工设计的折射率渐变层中进行了模拟,并对二者的结果进行了比较分析,发现这种折射率渐变层介质确实对点光源入射的环形光栅的自成像情况有着很好的改善.希望这一工作能够推广Talbot效应的应用范围. 相似文献