多层衍射光学元件设计原理与衍射效率的研究

叙述了多层衍射光学元件的设计原理.通过对多层衍射光学元件结构、位相延迟表达式、材料选择匹配的研究,使得优化最大光栅高度后的多层衍射光学元件能够实现大幅度提高宽光谱范围内衍射效率的作用.其衍射效率在从g谱线（435.834 3 nm）到C谱线（656.272 5 nm）的可见光范围内的任何波长上的理论衍射效率均在99％以上,带宽积分平均衍射效率为99.7％,能够满足高质量成像光学系统应用的需要,并利用该元件设计了长焦距复消色差物镜.     

A single diffractive optical element implementing spectrum-splitting and beam-concentration functions simultaneously with high diffraction efficiency

In this paper,a novel method is proposed and employed to design a single diffractive optical element(DOE) for implementing spectrum-splitting and beam-concentration(SSBC) functions simultaneously.We develop an optimization algorithm,through which the SSBC DOE can be optimized within an arbitrary thickness range according to the limitations of modern photolithography technology.Theoretical simulation results reveal that the designed SSBC DOE has a high optical focusing efficiency.It is expected that the designed SSBC DOE should have practical applications in high-efficiency solar cell systems.     

Mixed multi-region design of diffractive optical element for projection exposure system

The diffractive optical element (DOE) is widely used to generate various illumination modes in the projection lithography system. The working principle and design methods of the DOE are discussed in detail in this paper. A mixed multi-region design method is proposed to calculate the phase of DOE based on the poor spatial coherence of excimer laser, using the Gerchberg–Saxton (GS) algorithm. The DOEs generating circular, dipole and quadrupole illumination modes are designed and simulated by three different methods: single region design, repeated multi-region design and mixed multi-region design. The performance of these DOEs are compared and analyzed with these three design methods. The mixed multi-region design method is used to design the DOEs generating three illumination modes, the diffraction efficiencies are greater than 85%, and the non-uniformities of illumination are less than 3%. The analysis results indicate that the DOE designed by the mixed multi-region design can achieve higher diffraction efficiency and illumination uniformity of the far-field intensity distribution without modifying the GS algorithm.     

Design of refractive/diffractive hybrid optical elements for beam shaping with large diffraction pattern

Diffractive optics is an important technique for beam shaping with high light efficiency and strong diffraction pattern flexibility. Since the diffraction angle is limited by the unit size of the diffractive optical element(DOE),the size of the required diffraction pattern is always rather small. In this Letter, refractive/diffractive hybrid optical elements(RDHOEs) consisting of a DOE and a lens are used to realize beam shaping for a large diffraction pattern. The lens, as the component of the RDHOEs, can not only be concave but also convex,and the double sampling Fresnel diffraction algorithm is developed for the design of these two types of RDHOEs.The simulation and experimental results provide solid evidence to demonstrate the proposed method with the pure phase spatial light modulator.     

Large aperture continuous phase diffractive optical element to realize uniform focal spot

Uniform focal spot, with flat top, steep edge, low side lobe and high light efficiency, is required in many high power laser system. Using diffractive optical element (DOE) to realize such uniform illumination has many advantages, such as high light efficiency of pure phase modulation, strong flexibility of phase design and so on. A kind of hybrid algorithm based on hill-climbing and simulated annealing is utilized for phase design, owing to the strong convergence of the hill-climbing and the global optimization potential of the simulated annealing. A continuous phase DOE with diameter 100 mm has been fabricated by a rotating hollowed-out mask and ion-etching on the K9-glass substrate. The interferogram of the DOE is given to show the smoothness of the phase distribution. The intensity distribution of the focal spot are measured by a general CCD, and a series of attenuators are used to increase the dynamic range of the measurement. The results after data-processing show that the uniform focal spot with certain uniformity at the main lobe, sharp edge, low side lobe and without sharp peak at the zero order has been obtained.     

折衍射混合复消色差望远物镜中的色球差

一个正透镜、一个负透镜及一个衍射光学元件以不同的组合可以构成两种折衍射混合光学系统.当这两种系统消球差、彗差及复消色差后会产生不同的色球差.通过赛德尔像差理论,分析了这两种结构产生不同色球差的原因.计算表明当衍射光学元件以负透镜的平面为基底时产生的色球差为以正透镜的平面为基底时产生的色球差的7倍.对衍射光学元件以负透镜的平面为基底的情形,提出了减小系统色球差的解决办法,使系统色球差减小到0.307 mm.另外设计了一个传统复消色差光学系统,并和折衍射混合光学系统进行了比较,分析表明,衍射光学元件可代替传统光学系统中的特殊光学材料并使系统达到相同的成像质量.最后讨论了衍射光学元件的衍射效率对系统成像质量的影响.     

Using diffractive optical element and Zygo interferometer to test large-aperture convex surface

A valid method for measuring the large-aperture convex surface by using a curved diffractive optical element (DOE) and a Zygo interferometer is demonstrated experimentally. In this method, the direct use of source and high-resolution CCD camera of Zygo interferometer represents a major advance in the areas of adjustment. The DOE, fabricated by combining laser direct writing and lithography, results in higher accuracy, efficiency and lower cost for testing aspheric compared with other types of DOE employed. We have fabricated one optical test system and measured a 110-mm-diameter convex surface of errors 44.3 nm rms and 311 nm P–V.     

一种用于均匀照明的衍射光学元件设计的快速模拟退火法

介绍了一种适用于均匀照明的衍射光学元件设计的自洽迭代和优化混合的快速模拟退火法,它引入Tsallis正则分布以及相应的效用函数思想,可以在接近1%的时间内得到和传统模拟退火法有着相同均方差(MSE)的理想模拟结果.     

实现Nd:YAG光束匀滑的衍射光学器件的研制

 采用爬山-模拟退火混合优化算法与旋转镂空掩模板工艺,针对基频光与三倍频光,设计并加工出口径80mm的连续位相衍射光学器件。在脉冲工作的Nd：YAG激光器上,实验研究了器件的光束匀滑性能,获得了与设计尺寸相符合、边缘陡峭、但包含较大顶部调制的光斑。初步验证了衍射光学器件在固体激光器光束匀滑上的应用可行性。     

多色光大空间带宽积傅立叶变换透镜系统的设计

本文根据傅立叶变换透镜系统的像差要求，通过研究衍射器件的色差特性和初级像差特点，提出了多色光大空间带宽积的傅立叶变换透镜的系统结构。此系统采用无光焦度的衍射器件校正傅立叶变换主镜的球差，使系统得到最大空间带宽积；还采用谐衍射器件的设计方法，使系统可对多种相干光实现光学傅立叶变换。相对传统傅立叶变换系统而言，此衍射系统结构简单，性能好，可望在光学信息处理方面得到广泛的应用。     

投影光刻离轴照明用衍射光学元件的矢量分析

使用衍射光学元件(DOE)作为投影光刻照明系统实现离轴照明(OAI)的光束整形匀光器件,能够在保持较高照明效率的基础上精确控制OAI光束的形状及光强分布.在矢量角谱传输方法的基础上,建立了投影光刻用DOE的矢量分析模型,并对标量方法设计的DOE在偏振照明情况下的匀光与整形性能进行了分析.分析结果表明DOE在大角度衍射、...     

Optimization of 350× optical zoom lens with diffractive optical element

Through researching and validating, a set of optical designs using a diffractive optical element (DOE) and optimization process has been derived in this paper. We put forward a set of theories to solve the numerous quality issues in imaging and applied it to an optical design. For an optical design to be successful, it must comply with the standards of the optical system. Optical designers must also take into consideration imaging quality, wherein the most influential aspects are chromatic aberration and monochromatic aberration. We complied with systemic standards such as effective focal length and total system length. Diffractive Optical Element, based on the theory of wave phase difference, takes advantage of negative Abbe number, which might significantly eliminate chromatic aberrations of optics. Following the advanced technology applied to micro lens and etching process, precisely made micro DOE element now is possible to be manufactured in a large number. A 350× zoom lens with DOE is demonstrated in the proposal. The results show that regardless of whether chromatic aberration is axial or longitudinal, issues concerning the optical lens's chromatic aberration could be significantly reduced.     

Axial field shaping under high-numerical-aperture focusing

Kant reported [J. Mod. Optics 47, 905 (2000)] a formulation for solving the inverse problem of vector diffraction, which accurately models high-NA focusing. Here, Kant's formulation is adapted to the method of generalized projections to obtain an algorithm for designing diffractive optical elements (DOEs) that reshape the axial point-spread function (PSF). The algorithm is applied to design a binary phase-only DOE that superresolves the axial PSF with controlled increase in axial sidelobes. An 11-zone DOE is identified that axially narrows the PSF central lobe by 29% while maintaining the sidelobe intensity at or below 52% of the peak intensity. This DOE could improve the resolution achievable in several applications without significantly complicating the optical system.     

采用分步迭代算法设计制作衍射光学元件

 结合均匀照明相位器件的设计实例，介绍最新提出的基于迭代框架的优化方法，并应用该方法设计制作了16台阶的衍射光学元件并对其进行了测试，验证了设计原理及方法的正确性，且对加工中可能出现的误差进行了分析和讨论。测试结果验证了采用多台阶相位结构的设计方案能有效提高工艺宽容度。     

折衍二元光学用金刚石车刀设计

栏光效应是影响折衍元件衍射效率的一个重要因素,栏光效应与加工刀具有着密切的关系。分析刀具圆弧半径与栏光效应的联系、刀具参数与元件加工后的表面粗糙度的关系以及刀具耐用度等要求,设计了加工折衍二元光学元件的金刚石刀具,给出刀具加工里程数计算公式和车削实验结果。实验结果证明:设计的金刚石刀具能够满足折衍二元光学元件的产业化加工要求,刀具耐用度较强化前提高2倍多。     

衍射光学元件精密模压模具设计及预补偿

衍射光学元件较球面、非球面光学元件在校正色差方面具备较大优势,尤其是在红外光学领域,应用衍射光学元件可进一步增加光学系统的设计自由度。随着红外光学市场的进一步增大,常规的衍射光学金刚石车削技术难以满足大规模需求,精密模压技术成为解决上述问题的关键技术。模具设计是实现精密模压的重点,为了缩减模具设计周期,该文采用有限元仿真方法对模具进行预先设计及补偿,并试加工。采用单站式精密模压机对设计的模具进行了精密模压试验。模压试验结果表明:采用合理的工艺参数,能够实现衍射光学元件面形精度PV达到0.56 μm,位置误差<0.011 mm,环带高度误差<0.12 μm,验证了仿真预先补偿在衍射光学模具设计中的有效性。     

Simultaneous multicolor image formation with a single diffractive optical element

A design for a novel diffractive optical element (DOE) that can reconstruct three different intensity patterns when it is illuminated by three different wavelengths is presented. If the chosen wavelengths are red, green, and blue, full-color reconstruction capability is obtained. Reconstruction is achieved in the near field (Fresnel domain). Computer simulation results as well as experimental evidence are presented, proving the capabilities of this novel DOE design procedure.     

含三层衍射元件的60°视场折/衍混合头盔目镜

设计了一种含有三层衍射光学元件的60°视场头盔显示目镜,并给出了系统优化过程和结果.在整个视场和设计波段范围内三层衍射光学元件的衍射效率均在90%以上,提高了系统的光能利用率和像的对比度.此目镜光学系统的出瞳直径为8 mm,出瞳距离为22 mm.整个系统重量仅为8 g,总长度为26.8 mm,结构轻便紧凑,具有良好的光学性能,满足头盔显示目镜的使用需求.     

Diffractive-optics-based beam combination of a phase-locked fiber laser array

A diffractive optical element (DOE) is used as a beam combiner for an actively phase-locked array of fiber lasers. Use of a DOE eliminates the far-field sidelobes and the accompanying loss of beam quality typically observed in tiled coherent laser arrays. Using this technique, we demonstrated coherent combination of five fiber lasers with 91% efficiency and M2=1.04. Combination efficiency and phase locking is robust even with large amplitude and phase fluctuations on the input laser array elements. Calculations and power handling measurements suggest that this approach can scale to both high channel counts and high powers.     

Creation of a three-dimensional optical chain for controllable particle delivery

We propose a design for producing a conveyable quasi-periodic optical chain that can stably trap and deliver multiple individual particles in three dimensions at different planes near the focus. A diffractive optical element (DOE) is designed to spatially modulate the phase of an incoming radially polarized beam. For a tighly focused beam, a three-dimensional (3D) optical chain can be formed because of the difference in the Gouy phase shift from two concentric regions of the DOE. A desired number of particles can be stably tweezed one by one with individual 3D volumes in this trapping structure. By controlling the phase modulation of the incident beam, one can manipulate the interference pattern to accelerate and transport trapped particles along the optical axis in a prescribed way.