激光光束整形技术一般是指调制入射激光光束的波前分布，得到所需要的强度分布和传播特性。光束整形技术已成为当前国际光学领域的一个研究热点。随着空间光调制器的技术进步，光束整形技术得到了飞速发展，不再局限于固定的光学参数设计，而是可以通过计算全息图动态地调制光场，实现任意图案的光束整形。另一方面，飞秒激光由于其峰值功率高、热效应小，可产生各种非线性效应等优点，在激光加工、信息存储、生物医学成像等领域有重要应用，也非常依赖光束整形。飞秒激光通常并非单色光，其典型带宽为10 nm，在使用空间光调制器对其进行整形时会因为衍射产生色散，导致光束整形效果恶化。在飞秒激光双光子显微成像中，这一问题更为突出。 现有方法通常使用棱镜或光栅等器件来补偿光栅引起的色散，而对于计算全息图引起的色散问题至今没有较好的解决方法。本文研究了飞秒激光经过空间光调制器之后的色散规律，提出了基于计算全息的任意图案的高分辨率飞秒激光光束整形方法，并应用于生物医学显微成像领域。主要研究内容如下： (1)本文分析了飞秒激光经过空间光调制器衍射之后的色散规律，研究表明，衍射场的色散由空间光调制器固有的二维光栅结构引起的色散和加载的计算全息图引起的色散两部分组成，而全息图可以看作是不同周期与方向的光栅成分的叠加。 (2)根据飞秒激光经过空间光调制器之后的色散特征，将开普勒色散补偿模块引入到光束整形的色散补偿中，同时补偿了全息图的所有光栅成分的色散，从而全息图的色散得到消除；另外轴向色散也得到了一定程度的补偿。 (3)本文设计了基于计算全息的高分辨率飞秒激光光束整形方法，用GerchbergSaxton算法生成任意图案的计算全息图，用光栅补偿空间光调制器的光栅结构引起的色散，用开普勒色散补偿模块补偿全息图引起的色散，实现了高分辨率消色差的任意图案的飞秒激光光束整形。实验结果表明，该方法可以实现全视场达到或接近衍射极限的任意图案的飞秒激光光束整形，可适用的光谱带宽大致200 nm。 (4)通过计算全息可以实现光束任意位置的三维定位，本文将基于计算全息的任意图案的高分辨率飞秒激光光束整形方法应用于双光子生物显微成像，演示了三维随机扫描双光子显微镜功能，实现了19.23 kHz的快速无惯性三维随机扫描，并在脑片上成功获取了细胞图像。在放大倍数40X，数值孔径0.8的水镜下，横向分辨率达到0.75 μm，轴向分辨率达到3.22 μm，接近光学衍射极限。 本文研究结果表明，本文提出的高分辨率飞秒激光光束整形方法能够实现任意图案的宽带飞秒激光的光束整形，并有潜力应用于生物医学显微成像等多个领域。 关键词：光束整形 飞秒激光 计算全息 随机扫描

 Laser beam shaping is the process of redistributing the irradiance and phase of a laser beam of optical radiation. Laser beam shaping has become a hotspot in the field of optics. With the development of the spatial light modulator, laser beam shaping is no longer limited to a fixed optical parameter design, but can modulate the light field to arbitrary pattern dynamically via the computer-generated hologram (CGH). Otherwise, femtosecond laser is widely used in material processing, information storage, and biomedical imaging benefit from its high peak power, low hot effect and nonlinear effects, which depends on beam shaping. However, femtosecond laser is not strictly monochromatic and has a typical bandwidth of 10 nm, which will introduce dispersion when femtosecond laser diffracted by a spatial light modulator, and deteriorate the effect of beam shaping. This issue is more obvious in femtosecond laser two-photon microimaging. Usually, researchers use prisms or gratings to compensate the dispersion caused by the gratings. The dispersion caused by hologram is not solved so far. In this thesis, we research the dispersion law of femtosecond laser diffracted by the spatial light modulator, and propose a method of high-resolution femtosecond laser beam shaping of arbitrary patterns based on CGH, which is applied to the field of biomedical microimaging. The main works are summarized as follows. (1)The dispersion law of femtosecond laser diffracted by the spatial light modulator is analyzed, which is caused by the inherent two-dimensional grating structure of the spatial light modulator and the hologram, and the hologram can be regarded as the superposition of grating components with different periods and directions. (2)Base on the analysis of the dispersion law of femtosencond laser diffracted by the spatial light modulator, we introduce the Keplerian Dispersion Compensation Module (KDCM) into holography to compensate all the grating components of the hologram simultaneously. So that the dispersion of the hologram is eliminated, and the axial dispersion is compensated to a certain extent at the same time. (3)We develop the method of high-precision femtosecond laser beam shaping. The CGH of arbitrary pattern is generated by Gerchberg-Saxton algorithm. The dispersion caused by the grating structure of the spatial light modulator is compensated by a grating. The dispersion caused by the CGH loaded on the spatial light modulator is compensated by the KDCM. The high-precision and achromatic laser beam shaping of arbitrary pattern is realized. Experimental results confirm that the proposed method can be used to shape femtosecond laser beams into arbitrary patterns in the whole field of view with the resolution near the optical diffraction limit, and the applicable spectral bandwidth is about 200 nm. (4)Appling the method of femtosecond laser beam shaping to bioimaging, we developed a set of three-dimensional random scanning two-photon microscope, which realizes a fast noninertia three-dimensional random scanning with the speed of 19.23 kHz. Using the water immersion objective with magnification of 40X and numerical aperture of 0.8, the transverse resolution of the microscope is 0.75 μm, and the axial resolution is 3.22μm. In summary, the proposed method in this thesis can achieve high-resolution femtosecond laser beam shaping, and has potential application in many fields such as biomedical microimaging. Key words: Beam shaping Femtosecond laser Computer-generated holography Random access