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1.
李建龙  吕百达 《物理学报》2007,56(10):5778-5783
使用角谱表示和严格的模式理论研究了线偏振高斯光束通过特征尺寸与波长可比拟的条形浮雕光栅的传输,系统参数误差对浮雕层中光强最大值的影响.研究表明,光束在条形浮雕光栅各层中有不同的光强分布,浮雕层的介质填充部分中的光强明显高于展空部分的光强.光栅周期误差对浮雕层中最大光强的影响起主要作用.并利用模拟退火优化算法优化系统参数以控制出射光束的光强分布.  相似文献   

2.
啁啾超短脉冲光波照射下光栅Talbot效应的研究   总被引:2,自引:0,他引:2       下载免费PDF全文
王淮生 《物理学报》2005,54(12):5688-5691
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   

3.
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   

4.
不同结构光栅的衍射光强分布   总被引:2,自引:1,他引:1  
构造了不同折射率介质组成的透光元件A及元件A组成的光栅,并计算平行光垂直透过元件A及元件A组成的光栅时衍射光强的分布,通过实验演示了一些不同结构光栅的衍射光强分布.  相似文献   

5.
记录结构对体光栅各向异性衍射选择特性研究   总被引:3,自引:3,他引:0  
以静态体光栅各向异性衍射理论分析模型为基础,将与体光栅厚度有关的记录光强调制度引入到各向异性耦合波方程中.利用耦合波理论分析了光折变晶体中体光栅的各向异性衍射性能,研究了在不同初始记录光强比的条件下,记录光入射角的改变对光折变体光栅各向异性布喇格衍射性能的影响.结果表明:记录光入射角和记录光初始光强比均对体光栅的各向异性衍射具有选择性;与此相比,记录光入射角和记录光初始光强比对于体光栅各向同性衍射不具备选择性.  相似文献   

6.
四、强光自聚焦、自调制与自加宽效应 在普通弱光辐射通过一般透明光学介质时,由于线性电极化效应,折射率与入射光强无关,因此光束的传播特性不受光强变化的影响,而只由介质的光程分布所决定.在强激光入射作用下,由于三次非线性电极化效应的结果,使得光学介质的折射率发生了与入射光束光强分布有关的附加变化,从而导致光束传输特性的相应变化.由三次非线性电极化强度一般表示式出发,很容易导出介质在光波场强值E的强光入射作用下所引起的折射率变化为式中n2表示与入射光强(它正比于E2)成正比的折射率变化的系数,亦称为非线性折射系数.由上…  相似文献   

7.
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   

8.
关于折射率对散射光场分布影响的研究   总被引:1,自引:0,他引:1       下载免费PDF全文
根据Mie散射理论,采用理论计算和实验相结合的手法,研究了光散射现象以及散射介质的折射率对散射光场分布的影响.通过对空气中不同折射率的散射介质形成的散射光场光强的实验比较,论证了散射介质折射率的实部变化对散射光强的影响不大,其主要影响是通过对相位的变化来实现的,也即散射介质折射率的虚部变化对光强的影响很大,在实际应用中不可忽略.这一结论对以散射光场的分布为基础的各种研究具有一定的指导意义.  相似文献   

9.
光纤光栅啁啾化传感研究   总被引:6,自引:2,他引:4  
提出了光纤光栅啁啾化传感概念和传感机理,将光纤光栅微观分解为栅区长度范围的许多具有独立感知能力且彼此关联的有效作用子栅集,表述了有效作用子栅集与待测环境场空间梯度分布之间的对应关系,从而较好地解释了光纤光栅啁啾谱产生的内在机理.理论推导并实验验证了光栅啁啾谱各谱参量(波长、带宽和反射光强)与待测环境场(温度和应变)之间的对应关系,为利用单一光纤光栅实现多参量同时区分测量、任意非均匀空间分布场传感提供了科学有效的解决方法.  相似文献   

10.
本文主要分析缝宽不等且成周期性变化的光栅的衍射,给出其定量的光强分布规律,类比等缝宽光栅的衍射,引入"光栅的一个周期的衍射因子"与"光栅的周期间的干涉因子"的概念描述缝宽周期性变化的光栅的衍射光强分布.进一步,由Matlab仿真模拟了缝宽周期性变化的光栅的衍射相对光强分布曲线图,并定性讨论了光栅的相邻缝的间距d、缝宽、缝的数量等参数对光强分布的影响,从而更加形象、准确、多方位地分析变缝宽光栅的衍射规律.  相似文献   

11.
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   

12.
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   

13.
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   

14.
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   

15.
曹艳波  艾华 《中国光学》2010,3(6):679-683
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   

16.
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   

17.
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   

18.
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   

19.
 基于电磁场的多尺度变换理论,将一个各向异性介质椭球重构为一个各向同性介质椭球,进一步得到了新椭球的形体参数。利用各向同性椭球电磁场与各向异性椭球电磁场的多尺度关系,得出了各向异性介质椭球内电场的解析表达式,对所得结果进行了验证。计算了椭球内电场方向与外电场方向的夹角,仿真结果表明:外电场的方向对椭球内电场的影响不大,介电常数张量对椭球内电场的方向和大小有较大的影响。  相似文献   

20.
The nonresonant electromagnetic instabilities of the anisotropic velocity space (Weibel‐like) have always been one of the interesting subjects for researchers. These electromagnetic instabilities play an important role in generating strong magnetic fields in laboratory plasmas for applications such as inertial confinement fusion and space plasmas. In this paper, we investigate the quantum effects of the particle spin on the electromagnetic instabilities. In the case of the presence of a magnetic dipole force and an electron precession frequency like the Vlasov equation, we derive the full quantum equation. This study shows that, in the presence of the spin‐polarized effects, the growth rate of the instabilities is reduced compared to the classical cases and will not arise for low fractions of the temperature anisotropy for different values of the magnetic field. Indeed, it is expected that the probability of electron capture in the background magnetic fields and the effective collision with the particle increase because of the spin effect, so that a high portion of the electron energy is transmitted to the background plasma, and the temperature anisotropy governing the electron distribution is reduced.  相似文献   

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