准相位型光子筛设计

提出了一种准相位型光子筛。该准相位型光子筛通过改变暗环上小孔直径与带宽的比值,对焦点处的相位分布进行调制,使通过亮环和暗环上小孔的光波在焦点处发生相长干涉,生成聚焦光斑。该准相位型光子筛无需对基底进行特殊处理,即可完成相位型光子筛的制作,降低了加工难度。和普通振幅型光子筛相比,在相同最小加工尺寸的条件下,准相位型光子筛具有较大的数值孔径,可降低聚焦光斑尺寸。并且,和多区光子筛相比,在同样的最小加工尺寸及数值孔径的条件下,准相位型光子筛光斑尺寸及质量均优于对方。为大数值孔径光子筛设计提供了一种新的设计方法。     

Phase zone photon sieve

A novel diffractive optical element, named phase zone photon sieve (PZPS), is presented. There are three kinds of phase plates in PZPSs: PZPS1, PZPS2, and PZPS3. Each of the PZPSs has its own structure and is made on quartz substrate by etching. The three PZPSs have stronger diffraction peak intensity than a photon sieve (PS) when the margin pinhole and zone line width are kept the same. The PZPS3 can produce a smaller central diffractive spot than the ordinary PS with the same number of zones on the Fresnel zone plate. We have given the design method for and the simulation of PZPS and PS. PZPS has potential applications in optical maskless lithography.     

How to get Airy disc from Airy pattern

Airy pattern is formed by diffraction of a plane wave through a circular aperture in the far field with certain side lobes. It is shown that Airy pattern can be truncated at the first dark ring by a circular aperture to pick up the center spot (called Airy disc) without causing additional diffraction fringes, even in the very far field. This may be called zero field truncation technique. And is very useful in practice, for example, as a good quality optical source.     

Laser writing system for fabrication of diffractive optics elements

We report a laser writing system for fabrication of diffractive optical elements with He-Cd laser. The wavelength of the light source is 441.6 nm. The output beam is collimated into parallel light with uniform intensity distribution after passing through the spatial filter with a pinhole of 25μm and the collimating device. A microscopy objective lens with numerical aperture (NA) of 0.65 is used to focus the beam into a small diffraction spot. Any pattern can be written with this system. Experimental results are presented.The written gratings and the phase patterns were verified with a conventional optical microscopy and the Taylor Hobson equipment.     

Effects of mask-alignment error on point spread function for multi-level Fresnel diffractive lenses

The full aperture complex amplitude transmittance function of a multi-level diffraction lens with maskalignment errors was derived based on scalar diffraction theory. The point spread function(PSF) was calculated by the Kirchhoff diffraction integral. It is found that the radius of the Airy disk increases with the increase of the error in the direction of misalignment, and the image center shifts along the direction of misalignment. A fourlevel diffractive lens with a diameter of 80 mm was fabricated, and its PSF and diffraction efficiency of +1 st order were calculated and measured. The distribution of PSF is consistent with the calculated results, and the tested diffraction efficiency is slightly smaller than the calculated value; the relative error is 5.71%.     

激光束衍射极限倍数β的确定方法

针对实用中由于参考光束选择标准不统一导致同一激光束的光束质量衍射极限倍数β因子值不确定的问题,利用衍射理论对各种参考光束的远场衍射特性进行了计算和分析.根据研究结果建议,在测定激光束衍射极限倍数β时,参考光束拟统一选取为与被测光束发射孔径或面积相同的圆形实心均匀光束.     

A hybrid doubled achromat based on a photon sieve

Photon sieves are diffractive optical elements with large chromatic aberration. To correct the dispersion of a photon sieve, a novel hybrid doubled achromat combined a photon sieve and a refractive lens is proposed. The design of this achromat applies the opposite dispersive characteristics of diffractive and refractive elements. Two design examples for different bandwidths of 300 nm and 80 nm in visible spectrum are given. For analyzing their focusing properties, the intensity distributions both along the axis and at the focal plane are studied. The results illustrate that the achromatic design is achieved and the secondary spectrum can be corrected for a narrow bandwidth. And compared to traditional hybrid achromat, it can focus to a sharper spot.     

冷却储存环主环磁铁的准直测量

采用激光跟踪仪及配套带软件Insight对兰州重离子加速器冷却储存环主环磁铁进行了安装和准直。首先建立全局坐标系，用来确定从源体到实验环各子系统的理论原点的位置；而各个子系统又分别以各自的理论原点为基础建立局部坐标系，用来安装定位本系统内的各个元件；对各个子系统中的每一个元件还采用了元件坐标系。准直测量时，先在每块磁铁上焊接8个测量基准；然后对磁铁上的基准进行测量，以确定其在元件坐标系中的位置；再架设激光跟踪仪，测量主环控制网点，恢复主环局部坐标系，根据元件在主环局部坐标系中的位置及理论坐标，计算出相关的变换参数；转入元件坐标系，采用激光跟踪仪及Insight 软件显示实时测量坐标及其与理论值之差，其精度达到0.15 mm。     

高斯光束通过非线性介质后的远场衍射图样的研究

 利用菲涅尔－基尔霍夫衍射积分公式，对发散和会聚高斯光束通过薄非线性介质时形成的远场衍射图样进行了研究。模拟计算结果表明：当发散高斯光束通过自散焦介质或会聚高斯光束通过自聚焦介质时，远场均会出现中央较暗、向外围逐渐增强、分布尺度较大的粗衍射环；当发散高斯光束通过自聚焦介质或会聚高斯光束通过自散焦介质时，远场均会出现中心强度最大、向外围逐渐减弱、分布尺度较小的细衍射环。不同远场衍射图样归根结底是入射高斯光束因介质折射率变化造成的空间自相位调制及其波前曲率共同作用的结果。     

强聚焦条件下连续位相板散斑特性的矢量分析

连续位相板(CPP)经过透镜聚焦后,在焦平面上形成一个散斑场,散斑场的统计性质决定了CPP的束匀滑特性。当使用大数值孔径透镜聚焦后,傍轴近似不再成立,因此分析CPP焦斑特性时标量衍射理论不再适用。采用Richard-Wolf矢量衍射理论对强聚焦条件下的CPP焦斑进行了计算,在此基础上分析了矢量焦斑场的统计特性,讨论了焦斑的轮廓。结果表明,由于非近轴的原因,矢量分析得到的焦斑尺寸略大,且通过矢量分析后能够得到z轴方向的光场分量。散斑场的振幅分布满足瑞利分布特性,强度分布满足负指数分布特性,且矢量合成方向的光强分布会略微偏离负指数分布特性。     

空间激光通信中光强起伏尺度特征的数值分析

利用数值模拟的方法,定量地计算分析了空间激光通信中光强起伏问题,得到了准直光束与聚焦光束光强起伏相关距离（不均匀元半径）随大气相十长度变化的结果;进而分别从接收效率和性价比等不同的角度对激光通信系统接收孔径选取的参考因素进行了探讨。根据现代光通信对误码率的最低要求定义最佳接收孔径,计算分析了聚焦光束空间激光通信系统最佳接收孔径随大气相干长度r0的变化关系。结果表明,最佳接收孔径随大气相干长度的减小而迅速增大。对于聚集光束空间激光通信而言,在大气相干长度ro约为4cm的强湍流效应情况下,通信系统的接收孔径接近5倍艾里斑直径,才能满足国际电信联盟-电信标准部对光通信的最低要求。     

Characteristics of filament induced Dammann gratings fabricated using femtosecond laser

To establish optimal processing conditions for direct write fabrication of diffractive optical elements such as gratings, waveguides, lenses, we have investigated the effect of process parameters such as scan speed, numerical aperture (NA) of objective lens, pulse energy on the characteristics of the filament induced inside fused silica with a femtosecond Ti:sapphire laser. The optimum process parameters were used to fabricate a number of Dammann gratings, 6×6 array, having different thicknesses and number of layers. The performance of these optical elements was evaluated by measuring their diffraction efficiencies. All gratings fabricated were strongly birefringent, the zero order spot with high intensity was not separated from the spot array, and the intensity distribution of 6×6 spot array exhibited some degree of nonuniformity. The single layer Dammann grating fabricated with a thickness of 80 μm attained a maximum diffraction efficiency of 38.8%.     

卫星激光通信端机远场模拟及远场测试技术研究

卫星激光通信需要进行端机远场模拟及远场测试技术研究。在室内短距离模拟远场分布的测试系统中,可以采用透镜变换,在透镜焦平面处得到远场分布。实际测试时引入点光源及平面反射镜,保证焦面位置确定的准确性。模拟卫星激光通信端机平行出射光的远场光斑,经实验检测,光斑第一、二、三级暗纹直径与远场光斑理论值比较的相对误差均小于5%。这表明,该方案可以准确模拟和测试端机远场。该研究工作对卫星激光通信捕捉概率的研究、通信研究、光链路功率的实测核准以及端机性能的整体评估有重要意义。     

非傍轴矢量高斯光束的圆屏衍射

利用矢量瑞利衍射积分公式，推导出非傍轴矢量高斯光束圆屏衍射的解析表示式.非傍轴矢量高斯光束圆屏衍射的轴上场分布、远场表示式、自由空间中的传输公式，以及傍轴近似下高斯光束圆屏衍射的菲涅耳和夫琅禾费衍射公式可以作为一般公式的特例统一处理.数 值计算和比较实例说明了非傍轴矢量高斯光束的光强分布和远场特性.分析表明，在圆屏衍 射中，f参数和截断参数决定光束的非傍轴行为. 关键词： 传输光学 非傍轴矢量高斯光束 圆屏衍射 矢量瑞利衍射积分公式     

高衍射效率衍射望远镜系统的设计/加工及成像性能测试

为提高衍射效率,设计并制作了口径为300mm的衍射成像系统.该系统的物镜是由一块四台阶位相型菲涅尔波带片通过激光直写套刻和Ar离子束物理刻蚀技术在石英玻璃基板上加工而成.测试了衍射物镜的衍射效率,实验结果表明:衍射物镜在波长632.8nm处的衍射效率为66.4%,达到理论值的82%.搭建了衍射成像系统光路,分别采用10μm星点孔与分辨率板,测试了系统的成像性能.实验测得星点像直径为44μm,分辨率板的极限分辨率达到84lp/mm,接近该系统的理论计算值,表明该衍射成像系统具有较好的成像性能.     

Estimation of coupling efficiency of optical fiber by far-field method

Coupling efficiency to a single-mode optical fiber can be estimated with the field amplitudes at far-field of an incident beam and optical fiber mode. We call it the calculation by far-field method (FFM) in this paper. The coupling efficiency by FFM is formulated including effects of optical aberrations, vignetting of the incident beam, and misalignments of the optical fiber such as defocus, lateral displacements, and angle deviation in arrangement of the fiber. As the results, it is shown the coupling efficiency is proportional to the central intensity of the focused spot, i.e., Strehl intensity of a virtual beam determined by the incident beam and mode of the optical fiber. Using the FFM, a typical optics in which a laser beam is coupled to an optical fiber with a lens of finite numerical aperture (NA) is analyzed for several cases of amplitude distributions of the incident light.     

High-performance readout and recording by a combination aperture

A solid immersion lens combined with a conical dielectric tip exhibits good resolution and efficiency in reading and recording data marks on optical storage media. We demonstrate a combination aperture that produces ~200-nm full-width 1/e(2) spot size and achieves 50% optical efficiency in an edge-scan experiment. A comparison of recording with the combination aperture, with an unmodified solid immersion lens, and with a far-field system is made.     

大口径连续相位板远场光强的离线测试实验

为了准确测试和评价大口径连续相位板（CPP）元件的远场光强性能,根据激光装置需求建立了351 nm波长下大口径CPP远场光强离线测试系统,开展了330 mm330 mm口径CPP元件测试实验,并与标量衍射计算结果进行对比,分析了系统的测试重复性和测试精度。实测系统远场弥散斑大小为2.9倍衍射极限,可测试最大口径为圆形f600 mm和方形430 mm430 mm。测试系统在焦点2 mm范围内的能量集中度测试重复性优于0.2 %。计算和实验焦斑形貌及分布吻合,实测能量集中度比计算结果小0.85%、焦斑半径大13 m左右,差异由实测系统的时间匀滑作用引起,可通过缩短曝光时间和减小系统像差等措施进一步提高测试精度。     

10m大口径薄膜衍射主镜的色差校正技术研究

分析了薄膜衍射主镜的成像性能及色散特性,利用含有衍射面的反射式消色差光路校正了衍射主镜的强色散,使成像系统的工作波段达到40nm、视场达到0.02°,设计了10m口径、115.73m总长的短结构合成孔径薄膜衍射成像系统.结果表明,消色差光路将两边缘波长0.58μm与0.62μm之间的焦距差由5.34m减小到17.27μm.该研究提供了一种薄膜衍射主镜成像系统的设计方案,可为超大口径薄膜衍射成像系统的工程化研究提供参考.     

子束排列方式对固体激光器光束合成特性的影响

 建立了固体激光器矩形光斑光束合成的理论模型,对诺·格公司给出的2束、4束、8束合成实验结果进行分析,并通过数值模拟,得到了不同子束排列方式下合成光斑的远场图形。通过仿真模拟可以得出:排列结构影响远场光斑的形状;子束间距决定了合成光束远场光斑的衍射旁瓣的大小和多少。采用环围能量进行分析,研究了远场光斑中主瓣能量随激光阵列占空比的变化。结果显示,远场光束环围功率随子束间距的增大而逐渐下降,而且参与相干合成子束越多,下降越大。