基于液晶空间光调制器的激光束近场整形

激光器输出的光束光强通常为高斯分布,但在很多实际应用中,为了提高激光系统的整体利用效率,需要将高斯分布的光束整形为空间均匀分布的平顶光束。从能量守恒定律和等光程原理出发,分析了非球面镜整形系统,得到了面型相位分布,基于此原理利用纯相位型液晶空间光调制器实现了对近高斯分布光束的光强整形,获得了近"平顶"的光束近场分布,并利用哈特曼波前传感器测量了整形后的光束波前相位分布。     

半导体激光器拍摄全息图的研究

半导体激光器输出的光束为椭圆高斯光束,若直接用于全息照相非常不利.采用梯形棱镜对将半导体激光器输出光束进行整形,并且在输出光束束腰位置进行全息照相,拍摄的全息图效果非常逼真.     

基于非球面柱透镜的激光束整形

提出了一种基于非球面柱透镜的激光束整形系统.该系统采用一组正交放置的非球面柱透镜实现对高斯光束的整形,能够获得较大长宽比、等光强分布的矩形光束输出.理论分析了高斯光束整形原理,由能量守恒定律推导出高斯光束整形系统中任意光线在入射面和出射面的坐标变换关系,使用ZEMAX编程语言编写坐标变换的ZPL宏指令并生成优化函数,设计并优化了整形系统.仿真设计得到了光强均匀度高于95%,能量利用率在90%以上的准矩形光输出.结果表明该方法整形效果理想、计算量小、简单实用.     

TEA CO2激光器输出平顶模按厄米-高斯模的展开

TEA CO2激光器输出光束的能量密度分布一般为平顶型分布.为了给研究和分析TEA CO2激光器输出光束提供一种新的处理方法,采用FGB理论,对实验测量的一台TEA CO2激光器输出的实际平顶型光斑的能量密度分布按厄米-高斯函数进行了展开.根据展开结果,对TEA CO2激光器输出光束的空间分布特性进行了分析与讨论.初步证实了TEA CO2激光器输出光束的能量密度分布可以按厄米-高斯函数展开.     

二元振幅型面板用于光束空间整形

为了提高高功率激光系统的整体效率和充分利用光能,需要对前端注入的高斯光束进行空间整形,实现驱动器终端激光的均匀化输出.采用振幅型二元面板对激光光束进行空间强度整形,利用误差扩散法进行了理论设计,数值摸拟了整形效果,同时讨论了面板加工误差以及空间滤波器的小孔大小等因素带来的影响.根据理论设计,分别加工了反高斯透射率分布和抛物线透射率分布的二元面板,并进行了整形实验,实现了各自的整形功能,并做了误差分析.实验让明二元面板能对激光光束的空间强度分布实现了精确的整形.     

柱透镜和弯月透镜实现半导体激光器光束整形

针对半导体激光器的发光特点,设计了半导体激光器的光束整形系统。首先采用柱透镜准直和偏转沿Y轴发散的光束;然后再采用望远系统对X轴发散的光束进行准直和扩束;最后采用弯月透镜对发射光束压缩,实现半导体激光器的光束整形,降低光束发散角,提高光束质量。利用ZEMAX软件模拟系统,结果表明,整形后输出光束沿X轴和Y轴的发散角变为4.922mrad,输出光斑直径为1.2707mm,整形系统总长度为65.6618mm,各元件的最大直径为20.52mm,输出光束质量和系统结构都优于同类产品。     

基于液晶空间光调制器的激光束整形

采用相位混合算法(PMA)与平滑修正法相结合的混合算法,对激光发出的高斯光束进行整形,得到了均方误差和顶部不均匀度均明显降低的等光强分布。利用液晶空间光调制器(LCSLM)的相位调制特性,实现了对高斯光束的光束整形,获得了光强均匀分布的圆光束和矩形光束输出。得到的输出光束顶部不均匀度和均方误差都低于5%,能量集中度在90%以上。表明此方法是一种实时、可控和高效的激光束整形方法。     

激光器的部分相干性对光纤激光器阵列相干合成远场图样的影响

考虑光纤激光器阵列相干合成的远场分布时，一般都认为单个激光器的输出光束是理想的高斯光束，实际上受各种因素的影响，一般激光器的输出光束都是一部分相干光.从部分相干光的高斯-谢尔模型出发，首次推导出了当单个激光器的输出光束是部分相干光时，激光器阵列相干合成的远场光强分布模型，并给出了数值模拟计算结果. 关键词： 光纤激光器阵列 相干合成 部分相干光     

利用双折射透镜组实现激光束空间整形

为了提高惯性约束聚变高功率激光系统的整体效率和充分利用光能,需要将高斯分布的光束整形为空间均匀分布的平顶光束。本文从球面透镜的琼斯矩阵出发,利用光学传输矩阵对双折射透镜组空间光束整形系统进行了理论分析,数值模拟了整形效果,讨论了透镜组参量的选择以及中心加工厚度误差等因素带来的影响,并对该系统进行了实验研究。在实验中,利用该双折射透镜组整型系统实现了光束的均匀化输出。在神光Ⅱ第九路中,在近场静态工作条件下,可将光束填充因子从原来的66%提高到80%。     

高斯反射率输出镜改善光束质量的实验研究

非稳腔能产生大体积基模,具有好的空间选模特性,但在固体调Q激光器中,由于孔径光阑和热畸变的影响,非稳腔输出的横模并不光滑.使用高斯反射率耦合输出镜可较好地改善其输出光束质量,设计了平-凸非稳腔,使用Nd:YAG,电光调Q固体激光器进行实验,获得了较为平滑的远场光强分布,实验结果表明高斯反射率输出镜可较好地改善固体激光器中非稳腔输出光束质量.     

Analysis of mechanical vibrations through speckle interferometry: A phase-space approach

The goal of this paper is to determine hidden periodicities (spatial frequencies) into speckles patterns obtained in a diffuser after reflection of an unexpanded laser beam over an aluminum membrane by means of the so-called Wigner Distribution Function (WDF). These spatial frequencies are used to find the temporal frequencies at which the mechanic system is vibrating.     

超高斯光束在超短脉冲激光系统中的传输

 为了增大光束的填充因子及提高放大器的能量转换效率,设计了一种新型的空间4程放大器,该放大器包括四组由凹面镜组成的空间滤波器,它们构成一个全像传递系统。由于有实焦点,放大器置于真空系统中。放大前,入射的高斯光束首先通过一个软边光阑和一个空间滤波器,被整形为高阶超高斯光束,然后在放大器中进行放大和像传递。钛宝石晶体置于各空间滤波器的像面和物面上。实验表明,该放大器结构稳定,可以保持良好的光束质量,远场焦斑达到近一倍衍射极限。     

一种大面积高能激光光束参数的在线测量方法

 提出了一种大面积连续波高能激光光束参数的在线测量方法——环形光刀扫描测量法。该方法采用偏心安装的斜面环形光刀高速扫描反射，光电探测器阵列沿反射光圆周均匀布置探测，使得绝大部分被测激光沿原光路传播，只有少量取样光被反射到探测器阵列上。通过对采集得到的探测器响应信号进行空间映射计算和图像复原，得到激光束的光强分布参数。该方法可用于光束直径数百mm的高能激光光束测量，测量空间分辨率约2 mm，时间分辨率为30~50 ms。     

采用液晶空间光调制器进行激光光束的空间整形

提出采用液晶空间光调制器进行激光束的实时,可调控光束空间整形的新方法,研究了液晶空间光调制器的光学调制特性,用液晶空间光调制器衬时产生的软边切趾光阑与空间滤波器结合,有效地对任意光束进行空间整形,获得光束填充因子高,近“平顶”光强的光束近场分布。     

Self-adaptive spatial filtering by use of azo chromophores doped in low glass-transition-temperature polymers

We report on self-adaptive spatial filtering by combination of the self-adaptive polarization-rotation property of Disperse Red1-doped polymers with low glass-transition-temperature and Fourier-transform operation. Our system can be operated with only an action beam with object information and without a probe beam for image readout. Edge enhancement by the action beam-probe beam is demonstrated as an example of the system's application to spatial filtering.     

Detection of fatigue cracks in a beam using a spatio-temporal dynamical system identification method

The identification of fatigue cracks in a beam is investigated in this paper. It is shown that due to the influence of the elastic nonlinearity of fatigue cracks, the homogeneity, along the length of the beam, of the spatio-temporal dynamics of the vibrating beam is destroyed. By using spatio-temporal dynamical system identification techniques, a new approach is developed to detect this nonhomogeneity. The cracked beam is divided into several spatial regions and a coupled map lattice (CML) model is identified and verified in one of the regions using an orthogonal forward regression (OFR) least-squares algorithm. This CML model is then used to predict the dynamical behaviour of the other regions and in this way to detect the nonhomogeneity of the overall system.     

Holographic solitons in photorefractive dissipative systems

A new kind of holographic soliton is proposed for a photorefractive dissipative system consisting of a biased photorefractive crystal and a strong pump beam with a uniform spatial distribution in both transverse dimensions. The self-trapping beam in the system can evolve into a spatial soliton when it couples coherently with the pump beam by two-wave mixing. Unlike the holographic solitons recently proposed by Cohen et al. [Opt. Lett. 27, 2031 (2002)], the most unique features of the present solitons are that they have a fixed amplitude and width that are determined completely by the system parameters and that their existence conditions are independent of the polarity of the bias field. Numerical simulations show that these solitons are stable relative to small perturbations.     

空间相位调制对强非局域空间光孤子的影响

利用空间相位调制技术和数值分析的方法，讨论了高斯光束在强非局域非线性平板波导中的传输问题，发现只要介质的响应具有对称性,光束就会有相同的演化规律，可控的空间相位调制参数不仅能让光束自偏转还能实现分束，其全新特性在全光开关及分光器上有潜在的应用价值. 关键词： 强非局域空间光孤子 空间相位调制 光偏转 光开关     

Multiple incoherent gray photorefractive spatial solitons

We show that an even-number sequence of multiple incoherent gray photorefractive spatial screening solitons is possible. When the external voltage is small, only an incoherent Y-junction photorefractive spatial screening soliton is generated, corresponding to the lowest order in the even-number incoherent soliton sequence. When the external voltage is increased, the incoherent gray soliton beam splits into an even-number sequence of multiple incoherent gray photorefractive spatial screening solitons. For a given physical system such an even-number sequence of multiple incoherent gray photorefractive spatial screening solitons is obtained by either increasing the external voltage and decreasing the full width half maximum (FWHM) of the beam’s intensity or increasing the external voltage and decreasing the beam’s grayness.     

Numerical analysis of spatial distortions in a single-grating chirped pulse amplification system

A numerical study of spatial distortions of a laser beam after propagation through an optical single-grating chirp pulse amplification (CPA) system was developed. This study is based on numerical simulation using the ray-tracing model from Rayica module of MATHEMATICA and it relates the behavior of the aberrated beam in terms of spatial distortions (eg. spatial chirp and pulse front tilt) in case of grating incident angle variation. The results are relevant for different applications which use CPA systems with needs of high quality laser beam profile.