可调谐艾里光束及其传输特性

艾里光束是一种新型无衍射光束,解决了激光在传播过程中的衍射效应。基于艾里变换技术,介绍一种可以通过椭圆平顶高斯光束产生的新型艾里光束,即可调谐艾里光束。通过理论计算,可以看出调节椭圆平顶高斯光束的束宽比可获得单尾艾里光束,同时,可调谐艾里光束的尾长可以通过调节入射椭圆平顶高斯光束的阶数来控制。通过研究,当束宽比p=1时,艾里光束的加速方向沿x轴45方向;p=1/2时,加速方向沿x轴31方向,p=1/3时,加速方向为沿x正方向,可见调节束宽比p的大小可以改变艾里光束的加速方向。     

非傍轴截断平顶光束的质量因子

 使用功率密度的二阶矩方法和Li提出的平顶光束模型，推导出了非傍轴截断平顶光束的束腰宽度、远场发散角和光束质量因子的解析表达式。计算结果表明：非傍轴截断平顶光束的质量因子不仅与截断参数、光束阶数有关，而且与初始束腰宽度和波长之比有关；当截断参数趋近于0时，远场发散角趋于渐近值63.435°；对于光束阶数为1和截断参数趋于无穷大的特例，计算结果分别退化为非傍轴截断高斯光束和非傍轴无截断平顶光束的结果；功率密度的二阶矩方法可用于截断光束，并克服了光束质量因子的发散困难。     

基于圆偏振涡旋光束强聚焦的平顶光束的构成

由于圆偏振涡旋光束可以表征为柱坐标的径向矢量光束和角向矢量光束的线性叠加,因而在研究其聚焦特性时,必须考虑具有拓扑核的径向矢量光束聚焦后有角向分量和角向矢量光束聚焦后有径向分量。在修正关于圆偏振涡旋光束强聚焦公式的基础上,重新模拟计算了不同拓扑核的圆偏振涡旋光束的强聚焦特性。结果显示不仅单自旋手性的圆偏振涡旋光束聚焦能形成平顶光束,而且两束不同的自旋手性的涡旋光束的叠加聚焦也可以实现平顶光束。通过调节光束的振幅、束腰半径以及遮挡通光孔径可以有效地改变平顶光束的半宽。     

光学薄膜测量时平顶光束激励的表面热透镜理论模型

推导了调制的平顶光束激励下基于Fresnel衍射积分的表面热透镜理论，通过数值模拟，比较了平顶光束和高斯光束激励下样品内部温度场、表面形变场和探测光衍射信号的径向分布，分析了影响表面热透镜信号的实验参数.结果表明，在最佳探测位置，平顶光束激励下的表面热透镜系统比相同情况下高斯光束激励下的灵敏度高，最高时约2倍，更有利于薄膜吸收测量. 关键词： 表面热透镜 光学薄膜 平顶光束     

使用离焦望远镜系统合成轴上平顶光束的一种新方法

提出了用平顶多高斯光束作为理想光束和使用离焦望远镜系统合成轴上平顶光束的一种新方法.在近轴近似下,基于柯林斯衍射积分公式推导出轴上光场和入射光场的解析表达式,并做了物理分析.光束阶数N,平顶长度参数L,平顶中心位置z_c和纵向中心空间频率S_c对轴上光强分布的影响用数值计算例做了说明.比较表明,该方法优于文献中使用矩形函数模拟理想光束合成轴上平顶光束的方法. 关键词： 轴上平顶光束 平顶多高斯光束 离焦望远镜系统 傅里叶变换     

环状平顶光束的传输特性研究

利用偏心高斯光束相干叠加方法，建立了柱坐标系下环状平顶光束模型.采用广义强度二阶矩定义，推导出环状光束广义M2因子的解析表达式.利用广义衍射积分理论，给出环状光束经过近轴ABCD光学系统的传输公式，并进一步给出了环状平顶光束修正的菲涅耳数定义.分析了环状平顶光束在自由空间的传输规律.研究结果表明，该模型可统一描述基模高斯光束、环状高斯光束以及环状平顶光束.环状平顶光束的广义M2因子和环状平顶光束的传输特性与其阶数及遮拦比有关.     

反射式椭圆高斯光束平顶整形系统

为了将椭圆高斯光束整形为圆形平顶光束,设计了一种无中心遮拦反射式两镜整形系统。根据能量守恒思想,选择匀化洛伦兹函数作为出射光束平顶分布函数,建立了入射面和出射面之间的坐标变换关系;采用光程守恒原理和矢量形式的反射定律,推导了积分形式的整形系统两反射镜面形方程。利用数值解法计算出两反射镜的面形数据,经过光学设计软件仿真与系统参数分析,得到的圆形平顶光束在目标区域的照度均匀性大于95%。结果表明,这种整形系统可以明显提高椭圆高斯光束的平顶性,具有现实可行性。     

部分相干平顶光束经光阑衍射的偏振特性

根据光束的相干-偏振矩阵和传输理论，对部分相干平顶光束经正多边形光阑衍射的偏振特性进行了系统的研究.给出了部分相干平顶光束偏振度传输公式，并将高斯-谢尔模型光束以及部分相干平顶光束在自由空间传输的偏振度作为特例统一于一般表达式中.研究表明：部分相干平顶光束经光阑衍射的偏振特性与光阑截断参数、光束的空间相干性、衍射角、传输距离、平顶光束的阶数有关.     

光束质量对平顶衍射光学元件输出的影响

衍射光学元件（DOE）对入射光束的波长、束宽、光束质量等参数都有很高的要求,其中光束质量的影响无法直接通过相干光场的衍射积分得出。本文利用高斯谢尔模型（GSM）光束分析了光束质量对平顶衍射光学元件输出的影响。采用对称迭代傅里叶变换算法设计了输出平顶光斑的DOE。用模式分解的方法研究了不同光束质量的光束经该DOE后的输出光斑,发现光束质量因子增加会使输出光斑平顶区尺寸减小,导致DOE失效。从交叉谱密度出发,表明DOE的输出光斑是相干部分和非相干部分的卷积,其中非相干部分是导致输出光斑劣化的原因。给出了平顶衍射光学元件适用的最大M2因子与输入和输出光束尺寸之间的关系。给出了一种GSM光束整形DOE的设计方法,该方法有助于在低光束质量激光器中实现DOE的应用。     

离轴平顶高斯涡旋光束形成的合成光涡旋及其在自由空间中的传输

对两束拓扑电荷m_1,2=±1的平行、离轴平顶高斯涡旋光束在束腰面叠加形成的合成光涡旋及其在自由空间的传输做了研究.详细的数值计算和分析表明,合光涡旋的位置、数目和净拓扑电荷与光束的控制参数,包括相对位相,振幅比,束腰宽度比,相对离轴参数,光束阶数,以及传输距离有关,但拓扑电荷不总是守恒. 关键词： 奇点光学 合成光涡旋 平顶高斯涡旋光束 拓扑电荷     

Cross focusing of two coaxial cosh-Gaussian laser beams in a parabolic medium

In this paper authors have presented the cross focusing of two coaxial cosh-Gaussian laser beams of different frequencies in a parabolic medium. Starting from the expression for field distribution of cosh-Gaussian beams, differential equations for beam-width parameters of two beams have been established through parabolic wave equation approach and analytical solution for weak beam has been obtained. The effect of decentred parameter of strong beam on the behavior of beam-width parameter with the normalized distance of propagation for weak beam has been specifically considered. The results have been presented graphically and discussed.     

Effect of Critical Beam Radius on Self-focusing of cosh-Gaussian Laser Beams in Collisionless Magnetized Plasma

Effect of critical beam radius on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma under ponderomotive nonlinearity forms the main core of present work. To investigate propagation dynamics of cosh-Gaussian laser beams in collisionless magnetized plasma, well established parabolic equation approach under WKB and paraxial approximations is employed. Our study is crucially pivoted on the concept of critical curve and subsequent determination of numerical interval for decentered parameter to sustain the competition between diffraction and self-focusing during the propagation of laser beam. Additionally, in the present study an interesting feature in the self-focusing region of the critical curve has been attempted for different values of decentered parameter.     

复宗量双曲余弦高斯光束的束腰及其位置

 由复宗量双曲余弦高斯光束通过近轴-ABCD-光学系统传输公式，推导出了基于二阶矩定义的光斑尺寸的解析表达式，给出了复宗量双曲余弦高斯光束在自由空间传输和通过薄透镜时的光斑尺寸、束腰宽度及其位置的解析表达式，并进行了数值计算，对计算结果进行了分析和讨论，该方法可用于其它光束通过近轴ABCD光学系统的类似计算。     

部分相干双曲余弦-高斯光束的传输特性和空间整形

 通过加入高斯项的空间相干度，引入部分相干双曲余弦-高斯（ChG）光束，推导出部分相干ChG光束通过近轴ABCD光学系统传输的解析表达式，并用以研究其传输特性和空间整形。结果表明，部分相干ChG光束的光强分布不能保持传输不变性，其光强分布不仅与传输距离和离心参数有关，而且还与空间相干参数有关。在传输距离固定时，适当改变部分相干ChG 光束的离心参数和空间相干参数，可实现光束的空间整形。光束质量因子随空间相干性的增大和离心参数的减小而减小。高斯-谢尔模型光束和完全相干ChG光束可作为部分相干ChG光束的特例处理。     

Transformation and spatial shaping of partially coherent cosh-Gaussian beams through an astigmatic lens

Based on the propagation law of partially coherent beams, the closed-form propagation expression for partially coherent cosh-Gaussian (ChG) beams through an astigmatic lens is derived. The transformation and spatial shaping of partially coherent ChG beams through the astigmatic lens are studied and illustrated by numerical examples. It is shown that a suitable choice of the spatial coherence parameter and/or astigmatic coefficient, different beam profiles, such as Gaussian-like, flat-topped and bottle beam profiles, and beam profile with a central dip, at the geometric focal plane and at a certain plane are realizable.     

Elliptical cosh-Gaussian beams

Using tensor method, a new kind of light beams named elliptical cosh-Gaussian beam (EChGB) is introduced in this paper. An analytical propagation expression for the EChGB passing through axially nonsymmetrical ABCD optical systems is derived by using vector integration. The derived formula is easily reduced to the propagation formula of a fundamental Gaussian beam and that of a cosh-Gaussian beam passing through optical systems. Some numerical simulations are illustrated for the propagation properties of EChGBs through the nonsymmetrical optical transforming systems, and further extensions are pointed out.     

Effect of Critical Beam Radius on Self-focusing of cosh-Gaussian Laser Beams in Collisionless Magnetized Plasma

Effect of critical beam radius on self-focusing of cosh-Gaussian laser beams in collisionless magnetized plasma under ponderomotive nonlinearity forms the main core of present work. To investigate propagation dynamics of cosh-Gaussian laser beams in collisionless magnetized plasma, well established parabolic equation approach under WKB and paraxial approximations is employed. Our study is crucially pivoted on the concept of critical curve and subsequent determination of numerical interval for decentered parameter to sustain the competition between diffraction and self-focusing during the propagation of laser beam. Additionally, in the present study an interesting feature in the self-focusing region of the critical curve has been attempted for different values of decentered parameter.     

Beam Propagation Factor and Generation of Cosh-squared-Gaussian Beams

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Beam Propagation Factor and Generation of Cosh-squared-Gaussian Beams

A new light beam termed as a cosh-squared-Gaussian beam (ChSGB) which may be one of solutions of the paraxial wave equation for propagation in complex optical systems has been introduced. Their beam propagation factor (M2-factor) is derived and schemes to generate this light beams are proposed.     

Off-axial elliptical cosine-Gaussian beams and their propagation properties

In this paper, a new kind of light beam called off-axial elliptical cosine-Gaussian beam (ECosGBs) is defined by using the tensor method. An analytical propagation expression for the ECosGBs passing through axially nonsymmetrical optical systems is derived by using vector integration. The intensity distributions of ECosGBs on the input plane, on the output plane with the equivalent Fresnel number being equal to 0.1 and on the focal plane are respectively illustrated for the propagation properties. The results indicate that an ECosGB is eventually transformed into an elliptical cosh-Gaussian beam. In other words, ECosGBs and cosh-Gaussian beams act in a reciprocal manner after propagation.