Fabricating of aspheric micro-lens array by excimer laser micromachining

This work presents a unique method for fabricating aspheric micro-lens array based on a KrF 248 nm excimer laser micromachining with precise surface profile control. Based on a planetary contour scanning laser machining method along with a shading metal mask and sample movable stage, an array of micro-lenses with precisely controlled surface profiles can be fabricated. Each lens surface profile can be aspheric and pre-designed. Experiments have been carried out and the machining accuracy of each lens surface profile is examined. Good surface roughness and profile accuracy are observed.     

Excimer laser: a new tool for precision micromachining

The unique features of the pulsed UV light emitted by excimer lasers lead to a variety of innovative applications of this relatively new industrial laser type. The excimer laser is used for micromachining, surface treatment, microlithography and high-quality marking. The resolution of excimer laser processing is very high: typical structures of 100 m down to 0.2 m are produced. Moreover, typical ablation rates of about 0.1–1 m per laser pulse also allow extremely high precision in the depth of material removal.The most popular industrial applications of excimer lasers are microdrilling for highly integrated multichip modules (MCMs), TABs and FPCBs, in the manufacturing of nozzle plates for personal ink-jet printers, TFT annealing for flat panel displays, wire stripping for hard disk heads, and indelible marking for the aircraft, electronic and medical/health-care industries.In contrast to traditional and alternative methods, the use of excimer lasers allows fast and flexible production processes without pollution of the environment. Nearly all technical materials (plastics, ceramics, glass, metals, semiconductors, composites) and biological/medical materials can be processed by excimer laser methods.     

Ablation effects and mechanism of sintered silicon carbide ceramics by an ArF excimer laser

The ablation of sintered silicon carbide ceramics by an ArF excimer laser was studied. Three zones are generated: the ablation zone that presented molten morphology and was composed by the Si and C phase; the condensation zone formed by vaporized SiC; and the oxidation zone that showed the characteristics of thermal oxidation. The ablation depth and oxidation range increase linearly with fluence and pulses within 0.5-4 J/cm~2,but the normalized ablation efficiency is constant(3.60 ± 0.60 μm·mm~2/J). The theoretical photochemical ablation depth supplies 25% of the total depth at 1 J/cm~2 but decreases to 16% at 4 J/cm~2. The ablation is dominated by the photothermal effect and conforms to the thermal evaporation mechanism.     

New aspects of micromachining and microlithography using 157-nm excimer laser radiation

The use of F₂ excimer laser sources, emitting at 157 nm, constitutes a new promising tool for scientific, industrial and lithography applications. The 157-nm laser emission enables high-resolution processes and the high photon energy offers the unique possiblity of photoionizing molecules in a single step. Therefore a lower fragmentation or thermal loading takes place. The 157-nm radiation will enable fundamental research and development for deep UV (DUV) high-resolution optical microlithography in the manufacturing of integrated circuits. This is the next step from the technology of ArF lasers at 193 nm. Furthermore, benefits are expected for key technologies requiring high-resolution processing and the micromachining of tough materials like Teflon or fused silica for micro-optics fabrication. Such applications require F₂ excimer laser sources with high performance, reliability and efficiency. The world of nanotechnology is just beginning to reveal its potential.     

Ablation characteristics of aluminum oxide and nitride ceramics during femtosecond laser micromachining

Femtosecond laser ablation of aluminum oxide (Al₂O₃) and aluminum nitride (AlN) ceramics was performed under normal atmospheric conditions (λ = 785 nm, τ_p = 185 fs, repetition rate = 1 kHz), and threshold laser fluencies for single- and multi-pulse ablation were determined. The ablation characteristics of the two ceramics showed similar trends except for surface morphologies, which revealed virtually no melting in Al₂O₃ but clear evidence of melting for AlN. Based on subsequent X-ray photoelectron spectroscopy (XPS) analyses, the chemistry of these ceramics appeared to remain the same before and after femtosecond laser ablation.     

Characterization of microstructures induced in the workpiece of aluminum alloy by excimer laser micromachining

Excimer laser emitting at 248 nm is applied to produce microstructures on the surface of aluminum alloy. The surface morphology shows that hotspots and thermal fluidic structures both come to light. Two possible mechanisms of hotspots formation are proposed: near-field diffraction and interference, and extremely fast rapid thermal annealing. And for the formation of thermal fluidic pattern structure, a thin film model is applied.     

高重复频率XeCl准分子激光器

本文报道一台高重复频率XeC准分子激光器的结构及其特性。采用接地栅金属陶瓷闸流管开关和气体横向流动系统及自动紫外火花预电离的放电结构。该激光器最高单脉冲能量为200mJ,最高重复脉冲频率为107Hz,最大平均功率18W。     

高功率准分子激光系统光学设计

回顾并介绍了高功率准分子激光系统设计中需要综合考虑的两项主要技术——像传递技术和角多路技术。讨论了照明方式和激光振荡源的光束整形在激光系统成像光路设计中的重要作用,对多路放大技术及角多路放大技术形式进行了系统分析。多路激光非相干合束是角多路技术和成像技术对高功率准分子激光系统光学设计提出的特殊要求,在简要分析了透射阵列和反射式望远物镜两种实现多路激光合束的打靶光学系统基础上,提出了一种利用反射式打靶光学系统和一套光学延迟线阵列来同时实现角多路编码和解码的新型光路布局,给出了初步设计方案。     

高功率准分子激光系统光学设计

 回顾并介绍了高功率准分子激光系统设计中需要综合考虑的两项主要技术——像传递技术和角多路技术。讨论了照明方式和激光振荡源的光束整形在激光系统成像光路设计中的重要作用,对多路放大技术及角多路放大技术形式进行了系统分析。多路激光非相干合束是角多路技术和成像技术对高功率准分子激光系统光学设计提出的特殊要求,在简要分析了透射阵列和反射式望远物镜两种实现多路激光合束的打靶光学系统基础上,提出了一种利用反射式打靶光学系统和一套光学延迟线阵列来同时实现角多路编码和解码的新型光路布局,给出了初步设计方案。     

Quantum cascade laser-based spectrometer for high sensitive measurements of trace gases in air

A quantum cascade(QC)laser-based spectrometer is developed to measure trace gases in air.The proposed spectrometer is tested for N2O,and the results presented in this letter.This system takes advantage of recent technology in QC lasers by utilizing intra-pulse scan spectroscopy,which allows high sensitive measurement.Without calibration gases,the gas concentration can be calculated with scan integration and the corresponding values from the HITRAN04 database.By analyzing the Allan variance,a detection limit of 2 ppb is obtained.Continuous measurement of N2O sampled from ambient air shows the applicability of the proposed system for the field measurements of gases of environmental concern.     

新型高精度绝对重力仪

精密测量地球表面的重力加速度(g, 常用值9.81 m/s²) 是探测地球重力场的重要途径, 已广泛应用于计量、测绘、地质、地震与资源勘探等领域. 随着我国"2000国家重力基本网"和"中国地壳运动观测网络"的建成, 对高精度绝对重力测量的需求日益增加. 为深入研究现有绝对重力测量技术可能存在的系统误差, 并满足国内多个领域对高精度绝对重力仪的迫切需求, 自主研制T-1型可搬运式高精度绝对重力仪样机, 采用经典的真空自由落体方案, 通过激光干涉测量和数据拟合方法获得重力加速度值. T-1型绝对重力仪主要包括以下几部分: 高真空度自由落体装置、小型化激光干涉测量装置、超低频垂直隔振系统、高速信号采集系统、仪器控制与数据处理系统. 绝对重力测量的长度基准为稳频He-Ne激光器, 时间基准为铷原子钟, 这两项现有基准的测量不确定度都优于1× 10^-9. 测试结果表明, T-1型绝对重力仪在12 h内重力测值的标准差可优于1 μupGal (1 μupGal = 10^-8 m/s²), 测量结果的复现性优于3 μupGal, 可实现微伽量级不确定度的精密重力测量, 有望在我国多个关键领域发挥重要应用.     

高精度色度计的研制

介绍一种可用于精密测量颜色的新型光度计。它不但可测量光源或屏幕的色坐标、色温、亮度和照度,配上标准光源还可以测量物体色。该仪器采用单片机技术,配有标准串行接口,并带有充电电池,具有体积小、使用方便等特点。     

高精度声学模拟系统简介

介绍了一套声学模拟系统。系统用采计算机控制,主要由高精度定位子系统、信号收发子系统、环境与目标模拟子系统以及配套软件组成,初步具备开展水声学模拟实验和超声实验的能力。     

MRTD高精度测试和校准技术研究

围绕红外热像仪成像参数MRTD（最小可分辨温差）测试问题开展研究,介绍了MRTD的测试方法以及MRTD测试装置—红外热像仪评估系统的工作原理,详细分析了MRTD测试过程中,红外热像仪测试位置、差分黑体温差、差分黑体发射率和光学系统几何像差等因素对测试结果的影响。针对这些问题,提出了采用红外扫描辐射计对红外热像仪评估系统温差进行校准的方法,利用该方法对某空间频率下热像仪MRTD进行测试,并给出了测试结果,为热像仪MRTD参数准确测试提供参考。     

高精度消色差相位延迟器性能测试研究

基于偏振调制原理，搭建了一套测量菱体型消色差相位延迟器延迟量的实验系统.利用本系统对高精度消色差相位延迟器进行了性能测试，实验结果表明特殊角入射的高精度消色差相位延迟器的设计原理正确，具有良好的消色差性能.对该系统进行误差分析表明系统测量误差小于1%，具有较高的精度，能够满足菱体型相位延迟器性能测试的使用要求，具有实际使用价值. 关键词： 偏振 消色差 延迟器 高精度     

Rapid micromachining of high aspect ratio holes in fused silica glass by high repetition rate picosecond laser

We present multiple methods of high aspect ratio hole drilling in fused silica glass, taking advantage of high power and high repetition rate picosecond lasers and flexible beam delivery methods to excise deep holes with minimal collateral damage. Combinations of static and synchronous scanning of laser focus were explored over a range of laser repetition rates and burst-train profiles that dramatically vary laser plume interaction dynamics, heat-affected zone, and heat accumulation physics. Chemically assisted etching of picosecond laser modification tracks are also presented as an extension from femtosecond laser writing of volume nanograting to form high aspect ratio (77) channels. Processing windows are identified for the various beam delivery methods that optimize the laser exposure over energy, wavelength, and repetition rate to reduce microcracking and deleterious heating effects. The results show the benefits of femtosecond laser interactions in glass extend into the picosecond domain, where the attributes of higher power further yield wide processing windows and significantly faster fabrication speed. High aspect ratio holes of 400 μm depth were formed over widely varying rates of 333 holes per second for mildly cracked holes in static-focal positioning through to one hole per second for low-damage and taper free holes in synchronous scanning.     

高重复率XeCl准分子激光器的放电特性

本文报道紫外预电离放电泵浦的高重复率XeCl准分子激光器的放电特性,分析了放电参数的改变对放电过程的影响.最佳转换效率达2.2%.     

高功率准分子激光主振荡功率放大系统光学元件的稳定性

为了分析高功率准分子激光主振荡功率放大(MOPA)系统中各光学元件稳定性对靶面光斑定位精度的影响,建立了分析模型,利用分析结果指导高稳定性镜架设计以满足系统实验需求。根据高功率准分子激光MOPA系统特点,有效地简化了系统光路,建立了系统光路模型;按照系统打靶精度要求,利用三维坐标变换和光线追迹法,计算得到了系统单个光学元件稳定性对靶面光斑定位精度的影响规律;最后,对自行设计的镜架进行了稳定性测量。计算结果表明,反射镜的旋转变化和透镜垂直光轴的平移变化是影响靶面光斑定位精度的主要因素,且主放大光路中反射镜在X方向和Y方向上最大的变化范围分别不能超过0.8和1.6μrad。实际测量结果表明,设计的镜架在X方向和Y方向最大的变化范围分别为0.6和0.81μrad,满足系统实验要求。     

Micro-Gal laser absolute gravimeter based on high precision heterodyne interferometer

A micro-Gal absolute gravimeter based on high-precision and high-stability heterodyne interferometer is presented. The distance measuring technology of the gravimeter is studied in detail. The experimental results of distance measuring for a free-falling motion show that the high-precision heterodyne interferometer described in this paper can meet the demand of a micro-Gal absolute gravimeter with relative uncertainty of 6.4 × 10-9. Moreover, the heterodyne interferometer is more stable than the Mach-Zehnder interferometer (MZI) which is widely used in present absolute gravimeters.