用于红外焦平面的正方形孔径球面微透镜阵列研究

针对目前红外焦平面光敏阵列中存在的占空比小、光能利用率低的实际问题,展开了正方形孔径球面微透镜阵列制作及其与红外焦平面阵列集成应用的研究.本文从红外焦平面光敏阵列特点入手,对比分析了正方形孔径相比于传统圆形孔径微透镜阵列在光能利用上的优势.提出正方形孔径微透镜阵列激光直写变剂量曝光制作技术,建立光刻胶曝光数学模型和正方形球面微透镜面型函数,以此为基础,编制直写设备变剂量曝光控制软件;利用长春理工大的学复合坐标激光直写系统和等离子刻蚀机进行相关工艺实验,制作了阵列256×256、单元尺寸40×40μm2、球面半径60μm、单元间距1μm的红外石英微透镜阵列;并将其与相应阵列的碲-镉-汞红外光敏阵列进行集成.结果表明:微透镜的占空比达到95%,红外焦平面光能利用率从原来的60%提高到90%以上.由此得出结论:变剂量曝光制作微透镜技术是可行的,正方形孔径球面微透镜阵列代替圆形孔径微透镜阵列,对于提高红外探测器的灵敏度、信噪比、分辨率等性能具备明显优势.     

光刻胶热熔法制备的非球面微透镜的设计方法

为了进一步提高入射到光敏元上的光能,针对光刻胶热熔法制备的微透镜的非球面面形,提出了一种结合有限元光线追迹和拉格朗日乘子法的设计方法。给定焦距,用该算法可以自动计算出所需的微透镜面形。为了验证算法的精度,对圆形孔径的焦斑均方根半径进行了模拟和理论计算,二者较为吻合。对三次有限元光线追迹的点列图误差进行了估计。计算了会聚到320 pixel×256 pixel背照射紫外焦平面探测器光敏元上的能量集中度,比较了具有不同圆角半径的方形孔径蓝宝石微透镜的效率。结果表明,具有6μm圆角半径的方形孔径微透镜的能量集中度较高,为96%。     

折射微透镜阵列的非成象光学特性研究

本文针对微透镜阵列与红外焦平面阵列集成的应用,对折射性微透镜阵列的非成象光学特性进行了研究和总结.采用系统性能评价因子来衡量微透镜的聚能效率,分析了系统参数对会聚效率的影响,并用标量衍射方法对几何光学分析结果进行了校验,为红外焦平面阵列微镜集成的设计和制作提供了理论依据.     

正方形孔径纳米半球阵列提高LED光提取效率研究

为提高氮化镓(Ga N)基发光二极管(LED)的光提取效率,基于等效介质理论设计了底面100%占空比、半径为320 nm的正方形孔径纳米半球阵列。利用时域有限差分法(FDTD)对正方形孔径纳米半球阵列结构底面占空比、半径对光提取效率的影响进行了仿真计算研究。仿真结果表明:LED p-Ga N表面刻蚀半径为320 nm、底面占空比为100%的正方形孔径纳米半球阵列的光提取效率最优。采用电子束曝光配合热回流技术和ICP刻蚀完成正方形孔径纳米半球阵列的Ga N基LED制作及测试实验。结果表明:在20 m A和150 m A工作电流下,有微纳结构的LED较无微纳结构的参考样品的发光效率分别提高4.67倍和4.59倍,计算结果与实验结果比较一致,说明加入方形孔径纳米半球阵列可以有效提高LED光提取效率。     

六角形孔径平面微透镜阵列的制作及基本特性研究

采用光刻离子交换工艺制作了六角形孔径平面微透镜阵列.离子交换后的变折射率区域有微小重叠,填充系数可达95%以上.对制作的六角形孔径平面微透镜进行了折射率分布、数值孔径和像差等光学特性测试,得到的六角形孔径平面微透镜阵列光学性能均匀,成像质量较好的结果.该透镜阵列的研制成功为制作高质量高填充系数透镜阵列及模拟生物复眼光学系统奠定了基础.     

PtSi IRCCD器件用长焦距Si微透镜阵列的制作研究

为了改善PtSi IRCCD器件的红外响应特性,需要添加长焦距微透镜阵列进行焦平面集光,本文提出了一种新的方法—曲率补偿法用于长焦距微透镜阵列的制作.扫描电子显微镜(SEM)显示微透镜阵列为表面极为平缓的方底拱形阵列,表面探针测试结果显示用曲率补偿法制作的微透镜阵列表面光滑,单元重复性好,其焦距可达到685.51μm.微透镜阵列器件与PtSi IRCCD器件在红外显微镜下对准胶合,显著改善了IRCCD器件的光响应特性.     

多边形棒状透镜出端辐射均匀性的研究

研究了用多角形棒状透镜产生高均匀性正方形和圆形照明的最佳结构参量.结果表明,对于正方形棒状透镜,输出端的照明均匀性随透镜的长度振荡变化,在某些特定长度达到极小值.对于圆形照明面积,比较了从三角到八角的六种多边形.利用三角形积分透镜可以获得最佳的照明均匀性,但光能利用率相对较低,六角形积分透镜可同时获得较高的照明均匀性和光能利用率.     

石英微透镜阵列的制作研究

叙述了采用氩离子束刻蚀的方法制作线列长方形拱面石英微透镜阵列.所制单元石英微透镜底部的外形尺寸为(300×106)um²,平均冠高7.07μm,平均曲率半径202.19μm,平均焦距404.38μm,平均F₂数为3.82,平均光焦度2.47×10³屈光度,扫描电子显微镜和表面探针测试表明,所制线列石英微透镜阵列的图形整齐均匀,单元长方形拱面石英微透镜的轮廓清晰,表面光滑平整.所制微透镜阵列用于高T_c超导红外探测器阵列的实验证实,微透镜的引入可以显著改善超导探测器的光响应特性.     

紫外衍射微透镜阵列的设计与制备

为了提高紫外焦平面阵列的填充因子,可以通过微透镜阵列与紫外焦平面阵列的集成,以改善紫外焦平面阵列的探测性能。根据标量衍射理论设计了用于日盲型紫外焦平面阵列的128×128衍射微透镜阵列,其工作中心波长为350nm,单元透镜F数为F/3.56。采用组合多层镀膜与剥离的工艺方法制备了128×128衍射微透镜阵列,对具体的工艺流程和制备误差进行了分析,测量了衍射微透镜阵列的光学性能。实验结果表明:衍射微透镜阵列的衍射效率为88%,与理论值95%有偏差,制备误差主要来自对准误差和线宽误差。紫外衍射微透镜阵列具有均匀的焦斑分布,与紫外焦平面阵列单片集成能较好地改善器件的整体性能。     

用于并行激光直写的连续深浮雕衍射透镜阵列研究

研究了一种用于并行激光直写的连续深浮雕衍射透镜阵列方法.该方法采用连续浮雕衍射透镜阵列替换传统并行激光直写中的物镜阵列,在兼顾系统分辨力基础上,克服了波带片等衍射透镜阵列衍射效率低的缺点;同时因采用深浮雕结构优化环带宽度,可降低阵列的制作难度.针对并行激光直写系统阵列F/#小的特点,在建立连续深浮雕衍射透镜阵列非旁轴近似聚焦模型基础上,设计、制作和测试了波长为441.6 nm,F/#为7.5的连续深浮雕衍射透镜阵阵列.测试结果表明:该阵列的衍射效率优于70%,远高于波带片阵列的40%.     

Monolithic integration technique for microlens arrays with infrared focal plane arrays

Based on scalar diffraction theory, 8-phase-level 256×290 element diffractive microlens arrays with lenslet dimension of 50×33 μm² have been fabricated on the back side of PtSi infrared focal plane arrays. The design and fabrication process are discussed. The measurement results indicate that the imaging quality has been greatly improved and the ratio of the signal-to-noise of the infrared focal plane array integration with microlens array is increased by a factor of 2.5.     

Model analysis of effect of diffraction focus characteristics of microlens arrays on parallel laser direct writing quality

In order to study the effect of diffraction focusing characteristics of microlens arrays on the parallel laser direct writing quality, we use nonparaxial approximation to analyze the diffraction focus characteristic of a single microlens, take into consideration the cross-talk effect of a number of microlenses on the diffraction focusing characteristics of an array, and establish a theoretical focusing intensity model of a microlens array to describe the influence of a change in F-number and/or center distance on the diffraction focusing characteristics of a parallel laser direct writing system while incident writing laser is normal. Numerical simulation results indicate that there is a cross-talk effect among microlenses which increases as the F-number increases when the center distance is the same as the smaller aperture, and parallel writing quality can be improved by reducing or totally eliminating the cross-talk effect by reducing F-number and/or increasing center distance.     

Ultrathin Planar Microlens Arrays Based on Geometric Metasurface

Ascribing to the properties of two dimensional parallel focusing and imaging, low propagation loss, integration and miniaturization, microlens array has been widely used in imaging, optical communication, organic light emitting devices, adaptive optics, photolithography, biomedical and other applications. However, the existing traditional microlens array suffers from difficulty in fabrication, large‐thickness, curved surface, non‐uniformity of light spots, or requirement of additional discrete components to control the microlens. Herein, a planar microlens array is experimentally demonstrated based on the geometric metasurface. The single microlens is composed of space‐variant subwavelength metallic gratings with high polarization conversion efficiency and thus exhibits gradient phase distribution. The focused spot diameter of 22.5 μm with radius of 350 μm, focal length of 1 cm and the light spots intensity uniformity of 0.9885 (standard deviation 0.0115) at the focal plane are obtained. Moreover, the broadband property of microlens array is also confirmed. The novel design strategy for microlens array would facilitate the miniaturization of optical devices and be easily integrated in the optical interconnected devices.     

Microlens arrays for confocal microscopy

A new; high resolution measuring system based on confocal microscopy has been developed for the evaluation of microlens arrays; in particular for applications in confocal microscopy itself. Lenslet arrays for parallel scanning and processing in confocal microscopy were designed as phase-matched Fresnel lenslets and fabricated by direct laser writing. Replica arrays were produced by ultraviolet embossing and hot embossing techniques. Fabricated arrays with a numerical aperture of 0.28 exhibited near diffraction limited performance and a focal length standard deviation of 120 nm in a nominal value of 250 μm. The technique developed represents a convenient and powerful technique for the characterization of lenslet arrays in general.     

微透镜列阵提高红外探测器探测能力的方法研究

研究用微光学方法提高红外探测器探测能力的机理,通过实验将锗微透镜列阵耦合到180元HgCdTe焦平面红外探测器上,使耦合组件探测率提高到原来的2．8倍,提出的光学耦合效应概念为客观评价微光学聚能元件综合质量及耦合机构性能提供了一种新的方法。还对微透镜列阵的冷屏效应进行了讨论。     

高变倍比大相对口径长波红外变焦系统设计

针对传统红外连续变焦系统难以同时满足高变倍比和大相对口径的使用要求,通过采用复合变焦光学系统结构,增加传统红外连续变焦光学系统的变焦距范围和相对口径。基于长波红外320×240像元、25 μm×25 μm非制冷焦平面探测器,设计了一款高变倍比大相对口径长波红外变焦光学系统, 光学系统由一个连续变焦部分与两档变焦部分组成,通过引入衍射光学元件校正长焦端色差,工作波段为8 μm~12 μm,焦距变化范围为-9 mm~-272.25 mm,F数为1.4。该系统具有成像质量好、变倍比高、相对口径大、导程小和凸轮曲线平滑等优点。     

Three-dimensional integration of microoptical components buried inside photosensitive glass by femtosecond laser direct writing

We report the three-dimensional (3D) integration of microoptical components such as microlenses, micromirrors and optical waveguides in a single glass chip by femtosecond (fs) laser direct writing. First, two types of microoptical lenses were fabricated inside photosensitive Foturan glass by forming hollow microstructures using fs laser direct writing followed by thermal treatment, successive wet etching and additional annealing. One type of lens is the cylindrical microlens with a curvature radius R of 1.0 mm, and the other is the plano-convex microlens with radius R of 0.75 mm. Subsequently, by the continuous procedure of hollow microstructure fabrication, a micromirror was integrated with the plano-convex microlens in the single glass chip. Further integration of waveguides was performed by internal refractive index modification using fs laser direct writing after the hollow structure fabrication of the microlens and the micromirror. A demonstration of the laser beam transmission in the integrated optical microdevice shows that the 3D integration of waveguides with a micromirror and a microoptical lens in a single glass chip is highly effective for light beam guiding and focusing. PACS 42.62.-b; 81.05.Kf; 42.82.Cr; 82.50.Pt; 42.79.Gn     

Hybrid Integration Between Long Focus Microlens Array and IR Detector Array

A special method, named step simulation method, is proposed for fabricating Si microlens array to improve the performance of infrared focal plane array (IR FPA). The focus length of rectangle-based multistep microlens array with element dimension of 40 µm×30 µm is 885.4 µm by the method, which is much longer than the focus length of microlens array fabricated by conventional Fresnel binary optics technique., The large-scale 256×256 element microlens array is hybridintegrated with the PtSi Schottky-barrier IR FPA by optical adhesive. The test results show that diffractive spot size of the microlens is 17 µm×15 µm and the average optical response of the IR FPA is increased by a factor of 2.4.