衍射光学元件具有高衍射效率、高设计自由度、小型化和集成化以及能够实现任意形状的光束整形等优点，在诸如激光制造、光学操控、无线光通信、全息显示等领域有着广泛的应用，但仍存在关键性问题需要克服。论文针对衍射光学光束整形广泛存在的衍射图案尺寸受限、散斑干扰严重等问题开展研究，以改善光束整形性能并拓展实际应用。提出了基于球面波入射的可扩大衍射场采样区域的二次采样数值计算方法，利用GS算法实现了基于二次采样方法的光束整形，在不减小衍射光学元件单元尺寸的前提下，扩大了衍射图案尺寸，并且可有效抑制零级背景噪声，降低了加工难度和对入射光束质量的高要求。进一步将该方法拓展到折衍混合光束整形元件的设计，实现了大衍射图案的光束整形。充分挖掘二次采样方法的优点，提出了一种白光衍射光学光束整形技术，可将不同波长的入射光束整形成具有相同尺寸的衍射图案，解决了利用衍射光学元件进行光束整形时的波长选择性问题。利用LED为光源进一步改善了整形性能，并在室内多波段无线光通信的应用中，实现了白光LED的大衍射图案的光束整形。提出了一种抑制激光散斑的二维光束整形优化方法。通过逐步增强输入面的振幅约束条件，改进GS算法实现了二维光束整形并有效抑制了激光散斑。数值仿真和实验结果都充分证明了该方法的有效性。将抑制激光散斑的二维光束整形优化方法应用于激光冲击成形和全息投影。研制了激光冲击成形光束整形元件，进行了强激光冲击成形实验，实验结果表明，满足激光冲击成形实验对低频分布环形光束的需求。利用纯相位空间光调制器实现了高分辨率、低散斑噪声的全息投影。对于二值鉴别率板图案，抑制散斑使得分辨率提高了一倍。对于灰度图案，散斑同样得到有效抑制，结合时间积分法，可使用较少的子全息图就得到好的图像质量，大大缩短了积分时间，降低了对空间光调制器的高帧频要求，有望促进高质量动态全息投影的实现。

Diffractive optical elements (DOEs), with high diffraction efficiency, excellent design flexibility, properties of miniaturization and integration, can realize beam shaping with arbitrary diffraction patterns. So beam shaping with DOEs is widely used in laser direct casting, optical manipulation, wireless optical communication, and holographic display and so on, while there are some key problems should be solved for practical applications. In this thesis, the problems of the size limitation of the diffraction patterns and the speckles always existed in the diffraction patterns are focused to be solved to improve the performances and extent the practical applications of the beam shaping with DOEs. A double-sampling (DS) Fresnel diffraction algorithm with fast Fourier transform (FFT) is proposed to increase the sampling range on the output plane. A spherical beam with small value of the radius is used to illuminate a DOE, and the magnification of diffraction pattern is realized with DS based Gerchberg-Saxton (GS) algorithm. The proposed method can alleviate the fabrication complex of the DOE and the requirements of high quality illumination beam, and can effectively suppress the zero-order background noise. Furthermore, the DS algorithm can be used in the design of the refractive/diffractive hybrid optical elements (RDHOEs) to obtain large diffraction pattern.The advantages of the DS algorithm are exploited sufficiently, and the method of beam shaping for white light is proposed. With a DOE designed by the proposed method, the sizes of the diffraction patterns generated by different colors are the same. Furthermore, light-emitting diodes (LEDs) are used to further improve the performance of beam shaping. The proposed method is applied in the indoor wireless optical communication, and beam shaping with white LED is realized and large diffraction pattern is obtained.An optimization method for beam shaping to reduce speckles is proposed. By increasing the amplitude constraint on the input plane gradually, the new modified GS algorithm to suppress speckles is presented, and the design of two-dimensional DOEs for true beam shaping is realized. Numerical simulations and the experimental results are performed to demonstrate the effectiveness of the proposed method to suppress the speckles.The optimization method for beam shaping to suppress speckles is applied in the laser shock forming and the holographic projection. A DOE used in the laser shock forming is designed and fabricated, and the experiment of the laser shock forming is performed. The experimental result shows that the DOE meets the requirement of diffraction pattern with suppressed speckles in the laser shock forming. By using the proposed method, the high-resolution holographic projection with suppressed speckle noise is realized with the phase only spatial light modulator (SLM). As for the binary resolution test target, the highest spatial resolution of the reconstruction image is doubled compared to the existed iterative algorithm. As for the grayscale images, the reconstruction image is clear and the speckles are obviously suppressed. By using time-integrating speckle averaging technique, less sub-holograms are needed with the proposed method and the requirement of high frame rate devices can be loosen, which is useful to the holographic projection for motion pictures.