基于空间光调制器的飞秒激光深微孔加工方法

针对飞秒激光振镜加工系统中聚焦透镜焦深短等原因导致微孔加工深度不足的问题,提出了一种基于高损伤阈值空间光调制器加载菲涅尔透镜相位进行焦点轴向调控的加工方法 .通过加载不同焦距的菲涅尔透镜相位图,控制焦点以100μm为间隔进行焦点轴向位移,随着加工深度的增加控制焦点向下移动,并开展了相应的实验加工和测试.实验结果表明,采用该方法在保证高加工质量的前提条件下,在厚度为2 mm的不锈钢样件上实现了直径约为330μm的微孔加工.该方法开辟了二维振镜系统实现超深微孔加工的新探索,在激光加工领域有较好的应用前景.     

基于空间光调制器的动态全息再现技术研究

为了使空间光调制器实时产生大景深的再现像,运用GS算法计算出不同参数下的全息图。通过计算全息重建算法仿真得到不同傅里叶全息图下的再现像。在无傅里叶变换透镜的情况下,利用计算机将不同参数下的傅里叶全息图输出到空间光调制器,通过分析二维实时动态显示的再现像表明,当傅里叶全息图的采样点数为1 024×768,采样间隔为18μm时,再现像景深为275 cm,该参数下再现像景深最大;通过分析不同参数的傅里叶全息图再现像,实验结果表明相位图像元尺寸越小再现像景深越大,并且在相同参数下有傅里叶变换透镜时的再现像景深小于无傅里叶变换透镜时的再现像景深。     

基于液晶空间光调制器的光束变换研究

搭建了基于液晶空间光调制器的光束变换光路系统,介绍了一种通过编写程序来实现特定的光束强度分布的方法。利用MATLAB编写了闪耀光栅、菲涅尔透镜、环聚焦透镜、柱面菲涅尔透镜、小孔以及衍射调制板的灰度光栅图,并将其加载于液晶空间光调制器上,成功实现了光束变换。     

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。     

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。     

利用纯相位型液晶空间光调制器实现空心光束

为了提高激光系统的整体效率,需要将出射光强整形为空心分布。采用纯相位型液晶空间光调制器整形近高斯分布光强到空心分布。基于能量守恒定律和等光程原理,分析了纯相位型液晶空间光调制器光束整形系统,得出了整形系统所需的相位分布。采用衍射光学方法,数值模拟了整形效果,讨论了入射光束束腰半径和强度分布等因素对整形效果的影响。利用纯相位型液晶空间光调制器实验实现了空心光束,实验测得的转换效率大于99%。     

利用纯相位型液晶空间光调制器实现空心光束

为了提高激光系统的整体效率,需要将出射光强整形为空心分布。采用纯相位型液晶空间光调制器整形近高斯分布光强到空心分布。基于能量守恒定律和等光程原理,分析了纯相位型液晶空间光调制器光束整形系统,得出了整形系统所需的相位分布。采用衍射光学方法,数值模拟了整形效果,讨论了入射光束束腰半径和强度分布等因素对整形效果的影响。利用纯相位型液晶空间光调制器实验实现了空心光束,实验测得的转换效率大于99%。     

单晶硅空间光调制器

详细介绍快速响应单晶硅空间光调制器件的结构、工作机理、制作工艺、性能参数。空间光调制器的极限分辨率为４０ｔｐ／ｍｍ，口径为４０ｍｍ，在９３０ｍｍ写入光灵敏度为２０μＷ／ｃｍ＾２，响应时间为１５ｍｓ，给出该器件的应用实例。     

基于空间光调制器的光束大角度扫描技术研究

为实现一束激光在90°锥形范围内的扫描,利用液晶空间光调制器在光束偏转控制时精度高、无机械惯性等优点,研究并建立了基于液晶空间光调制器的光束偏转和角放大光路系统。提出了空间光调制器的可编程相位调制算法和角放大光路结构,推导了空间光调制器光束偏转角度与相位灰度驱动图的关系,设计了角度放大倍率高于22倍的角放大光路系统。在此基础上,建立了光束扫描控制实验系统,对该装置角度出射范围进行了测量,将实际的角放大倍率与设计值进行对比。实验结果表明:研制系统的出射视场角可达91.22°,并可通过畸变校正实现出射视场角范围内的规则形状扫描。该研究在光束敏捷控制、无线激光通信、目标搜索与追踪等领域具有重要的研究价值和应用前景。     

实时图像边缘增强空间光调制器

光学相关识别中首先需要一个把非相干到相干光进行转换的输入图像转换器，然后，再进入输入图像的边缘增强预处理，我们研制的光寻址单晶硅液晶光阀能够同时完成这两项功能。给出图像边缘增强的实验结果。     

Parallel direct laser writing of micro-optical and photonic structures using spatial light modulator

Two-photon polymerization (2PP) is a powerful tool for direct laser writing of micro-optical and photonic structures due to its flexibility in 3D structuring and sub-micrometer resolution. However, it can be time consuming to fabricate arrays of micro-optical devices and complex photonic structures. In this study, we propose to use predefined patterns (PPs) for parallel 2PP processing. A PP contains a multiple focal spot pattern optimized for the fabrication of certain microstructures. PP can be created by holographic laser beam modulation with a spatial light modulator (SLM). The quantity and position of the multiple foci can be flexibly and precisely controlled by predesigned computer generated holograms (CGHs). With these specially designed PPs, parallel fabrication of arbitrary distributed microlens arrays and 3D photonic structures is demonstrated. This method significantly improves throughput and flexibility of the 2PP technique and can be used for mass production of functional devices in micro-optics and photonics.     

Intense femtosecond pulse shaping using a fused-silica spatial light modulator

We present the design concept of a setup of a pulse shaper to be used for high-power femtosecond lasers. The pulse shaper is constructed from a high-damage threshold fused-silica spatial light modulator and a 4-f optical system based on the design concept to avoid optical damage. We have successfully demonstrated a pulse compression of 20 fs, 5 mJ pulses obtained from a 1 kHz repetition rate Ti:sapphire chirped pulse amplification system at an average power of 5 W.     

Display method with compensation of the spatial frequency response of a liquid crystal spatial light modulator for holographic femtosecond laser processing

Liquid crystal spatial light modulators, which are widely used as display devices for computer-generated holograms, have modulation characteristics that depend on spatial frequency. We describe a method for displaying a computer-generated hologram on a liquid crystal spatial light modulator with compensation of its spatial frequency response. Using this method, we demonstrate a binary phase grating with smaller dependence on the spatial frequency. We also demonstrate application of the display method to holographic femtosecond laser processing.     

Efficient speckle-free laser marking using a spatial light modulator

An approach for laser marking surfaces using a liquid–crystal-based spatial light modulator (LC-SLM) for beam patterning and manipulation is presented, designed to avoid the speckle interference problem which is a typical drawback of current SLM-based laser marking processes. In our approach, the LC-SLM is used to generate complex two-dimensional micropatterns (e.g., 20 × 20 datamatrices) with overall dimensions of < 320 by 320 μm. The micropatterns are generated in a series of 16 steps, using a Fresnel zone lens (FZL) combined with a computer-generated hologram (CGH); for each step the whole kinoform (FZL + CGH) is spatially shifted off-axis by a different amount of pixels to build-up the required pattern. In comparison with other SLM-based laser marking approaches already reported in the literature, our method not only eliminates (or at least significantly reduces) unwanted speckle interference but also reduces the laser power required for marking.     

Diffraction-based femtosecond pulse shaping with a two-dimensional spatial light modulator

A new diffraction-based method is proposed and demonstrated for simultaneous shaping of both the phase and amplitude of femtosecond laser pulses by use of a phase-only two-dimensional spatial light modulator. The method suppresses certain types of temporal replica features ordinarily observed in femtosecond pulse shaping owing to imperfections in modulator devices and allows for multiplexed outputs suitable for use in various applications.     

液晶空间光调制器在飞秒脉冲色散补偿中的应用

关键词：     

Compatibility of temporal multiplexed spatial light modulator with optical image processing

The tendency today is to replace high-dynamic light modulators by high-speed binary ones (of which the micromirror is the best example). This kind of spatial light modulators (SLM) fulfils all the present needs in displays. They are used in optical communications as binary systems and also in display applications (video projectors) with temporal multiplexing, in order to generate greyscale or colour images. In optical processing, and in the majority of coherent applications, temporal dithering introduces some distortions. In this paper, this point is studied with simulations. We point out that temporal multiplexing cannot be used in the Fourier plane. In the imaging plane, the distortion is weak if the filter has a positive impulse response.     

Cell culture device using spatial light modulator

Spatial light modulator is introduced for cell culturing and related illumination experiment. Two kinds of designs were used. The first type put the cell along with the bio-medium directly on top of the analyzer of the microdisplay and set a cover glass on it to retain the medium environment, which turned the microdisplay into a bio-container. The second type introduced an optical lens system placed below the spatial light modulator to focus the light spots on specific position. Details of the advantages and drawbacks for the two different approaches are discussed, and the human melanocyte cell (HMC) is introduced to prove the feasibility of the concept. Results indicate that the second type is much more suitable than the first for precision required application.     

Fiber-optic confocal microscopy using a spatial light modulator

We present a novel fiber-optic confocal microscope in which the scanning operation is achieved by use of a spatial light modulator (SLM) to sequentially illuminate individual fibers or patterns of multiple fibers. Experimental images are presented, and the optical-sectioning capability of the device is demonstrated. The novel SLM-based system is more optically efficient, achieves higher contrast, and has improved optical-sectioning capabilities compared with those of other proposed instruments for confocal microendoscopy.     

PIV analysis using an optically-addressed spatial light modulator

An optical processor for generating a two-dimensional squared auto-correlation function is proposed in this paper. The incoherent-to-coherent conversion is performed by an optically-addressed spatial light modulator. The processor is meant to be used as integrated part of a system for post processing Particle Image Velocimetry (PIV) photographs of fluid flows. The optical processor to be able to present a fast and comparable alternative to the numerical processors, which typically are used for this purpose. This work demonstrates that the priciple is very promising.