Fizeau激光波长计测量脉冲激光波长

详细讨论了采用单片机控制的Fizeau波长计测量脉冲激光波长的两种方法,包括脉冲激光同步测量方法与软件判别捕捉方法,文章最后给出了系统的测量结果,其测量精度与测量连续激光相同,即绝对精度<10^-6,分辨率<10^-7.     

高灵敏度腔增强吸收式乙炔气体检测系统

基于超窄线宽激光特性和光源波长扫描技术,构建了高灵敏度腔增强吸收式乙炔气体检测系统。该系统采用超窄线宽可调谐半导体激光器作光源,使用两块高反射率平凹透镜组成的光学谐振腔作吸收池,通过扫描腔长使入射激光频率与谐振腔模式相匹配,利用激光失谐技术快速断开入射激光,从而实现对微量乙炔气体浓度的衰荡测量。利用腔增强吸收技术测得了激光衰荡时间和6 518.824 cm^-1附近的乙炔弱吸收光谱并进行了分析。结果表明,乙炔气体浓度线性相关系数优于0.999,最大相对误差小于2.5%,极限检测灵敏度为2×10^-6;逐次充入一定体积的乙炔气体,动态响应时间均小于10 s。该检测系统精确度好、灵敏度高,具有较好的动态响应特性,可用于电力变压器故障气体实时在线监测。     

一种新的高分子聚合物光限幅特性的实验研究

报道了一种具有σ-π电子共轭轨道的硅聚合物的光限幅特性.在532nm波长,测量了不同浓度下样品的透射率与光强的关系.实验结果指出该聚合物具有较好的光限幅特性.利用Z扫描方法测定了该样品的有效双光子吸收系数β=3.5×10^-9cm/W.     

软X射线—真空紫外反射率计

软X射线-真空紫外反射率计系统由光源、单色仪、反射率计、电子学及微机控制系统等几部分组成。可完成各种光学镜面、光栅、成像系统等的性能评价工作,反射率计真空室直径φ800mm,长1200mm,工作波段25～100nm,更换光源和探测器可扩展到1～250nm,角分辨率0.03°,扫描范围0～90°。     

扫描力显微镜中超微力的探测方法

本文介绍了近十年来,各国科学家在研究扫描力显微镜的过程中所采用的各种超微力(10^-8～10^-10N)传感器的探测方法。评述了各种方法的灵敏度,抗振性,使用范围,操作方式和各自的优缺点。并对最近出现的几种新的探测方法作了说明。     

光谱范围从365至12000nm的高精度光电自动折射仪

介绍了由作者研制的光谱范围从365至12000nm的高精度光电自动折射仪的测量原理、主要误差源和仪器组成。用该仪器对包括红外材料锗在内的多种样品进行了测量,在小于2600nm和大于2600nm的波长范围内分别获得了优于±3×10^-6和±5×10^-5的折射率测量精度。     

单价银离子在 CaO-P2O5 系统玻璃中的发光特性

在弱还原气氛下制备了单价银离子(Ag⁺)掺杂的CaO-P₂O₅系统玻璃,测试了其在室温下的吸收光谱、激发光谱和发射光谱。Ag⁺-CaO-P₂O₅玻璃的吸收光谱表明两个吸收峰。高能峰位于220nm波长,由4d¹⁰→4d⁹5P¹跃迁引起,低能峰中心位于240nm波长,归因于4d¹⁰→4d⁹5s¹跃迁,该吸收与其发射特性有关。紫外波段的宽带吸收产生了可见波段强烈的荧光发射,发光峰位于440nm波长,半宽度为130nm.研究了掺质浓度与发光特性的关系,随着掺质浓度的增加(0.05～0.25mol%),发光峰向较长波段移动。在Ag₂O含量为0.5mol%时,出现了浓度猝灭现象。为了比较起见,同时还研制了Cu⁺-CaO-P₂O₅及Cu⁺-Ag⁺-CaO-P₂O₅玻璃。     

紫外-可见光双通道拉曼光谱仪光学设计

紫外拉曼光谱技术具有高强度拉曼散射、无荧光干扰的特点;可见光拉曼光谱技术可实现低波数、高分辨率探测。为兼具两种激发波长的优势,设计了一款对称分布的双Czerny-Turner光路聚焦于一个探测器的双通道拉曼光谱仪。通过元器件的选型和初始结构的计算,在不增加多余元器件的情况下,对弧矢方向像散进行补偿,避免了像面上的能量损失。配合Zemax软件对双通道光谱分别进行建模优化,最终实现了对400~5000 cm^-1（266 nm激发）和50~3500 cm^-1（633 nm激发）两段光谱的同时探测。均方根半径、点列图和调制传递函数等评价指标有效验证了设计的合理性和可行性。结果表明,两套拉曼光谱仪分别可达8 cm^-1和5 cm^-1分辨率,本设计具有高分辨率、低波数、多波长激发、集成化等优势。     

半导体载流子分布的太赫兹近场显微表征

基于自建的太赫兹散射型扫描近场显微镜系统（THz s-SNOM），研究了其在显微表征半导体载流子浓度分布中的应用。对基于半导体硅的静态随机存取存储器（SRAM）的纳米结构进行了近场显微成像测量，并采用可见光调控本征硅样品表面的载流子浓度，实现了不同浓度（10¹⁴～10¹⁷ cm⁻³）光生载流子的近场检测。结果表明，此THz s-SNOM能够对半导体微纳结构的载流子分布进行高空间分辨率的显微表征，测量结果与基于偶极子模型的计算结果具有较好的吻合度。     

红外分光计:液氦冷却火箭运载圆形渐变泸光器

这里密述ICECAP极光测量计划所用一种红外分光计、从高度45公里到200公里的火箭上取得大气发射光谱,这仪器连续扫描6.75—23.2微米光谱区,扫速为2次扫描/秒,仪器使用一个圆形渐变滤光器(CVF),光谱分辨率从3%到4%.全部光学组件、矽砷探测器、CVF、Irtran6透镜、挡壳、可卸的冷却罩装在一个高真空杜瓦瓶系统内冷却到10k以下,分光计在22微米处噪音等效光谱辐射(NESR)优于1×10^-1(W厘米^-2球面度^-1微米^-1).两次火箭飞行观察到高空大气发射占优势的是9.6—微米O₃和15微米CO₂.     

一种光学玻璃折射率自动测量方法

本文研究了一种折射率自动测量方法。可对紫外、可见,红外光谱折射率作自动精密测量。在光源稳定情况下,可见光测量精度可达±3×10^-6。该方法以最小偏向角方法为依据,以外反射像引导接收器,使其自动跟踪至最小偏向角的精确位置,最后给出样品的折射率。整个测量系统采用微计算机完成自动控制、采集及处理。该方法还可进行角度自动测量。     

CW可调谐单频环形染料激光器β-BaB2O4晶体内腔倍频

本文论述了利用β-BaB₂O₄晶体进行内腔连续波环形染料激光器倍频,获得了可调谐单频紫外相干辐射。在292nm附近,用3WAr⁺激光(全谱线)泵浦,得到非线性转换系数～8.33×10^-4W^-1。通过改变相位匹配角,在288～302nm范围内输出连续可调谐紫外谐波。β-BaB₂O₄晶体角灵敏度～27cm^-1/mrad。     

超低透过率的测定

本文介绍了用波长为632.8nm的He—Ne激光器作为光源测量透射比小于10^-7/cm²的X光滤光片针孔透射比的方法。为了测量这样低的透过率,我们设计和安装了反射式超低透过率测定装置。用黑色玻璃作为反射式衰减元件,用光电倍增管作为接收器,用数字电压表作为读数仪表。同时,还用中性玻璃滤光片组作为透过式衰减器,也测量了超低透过率。两种方法都得出满意的结果。     

Reconstruction of a scanned topographic image distorted by the creep effect of a Z scanner in atomic force microscopy

We analyzed the illusory slopes of scanned images caused by the creep of a Z scanner in an atomic force microscope (AFM) operated in constant-force mode. A method to reconstruct a real topographic image using two scanned images was also developed. In atomic force microscopy, scanned images are distorted by undesirable effects such as creep, hysteresis of the Z scanner, and sample tilt. In contrast to other undesirable effects, the illusory slope that appears in the slow scanning direction of an AFM scan is highly related to the creep effect of the Z scanner. In the controller for a Z scanner, a position-sensitive detector is utilized to maintain a user-defined set-point or force between a tip and a sample surface. This serves to eliminate undesirable effects. The position-sensitive detector that detects the deflection of the cantilever is used to precisely measure the topography of a sample. In the conventional constant-force mode of an atomic force microscope, the amplitude of a control signal is used to construct a scanned image. However, the control signal contains not only the topography data of the sample, but also undesirable effects. Consequently, the scanned image includes the illusory slope due to the creep effect of the Z scanner. In an automatic scanning process, which requires fast scanning and high repeatability, an atomic force microscope must scan the sample surface immediately after a fast approach operation has been completed. As such, the scanned image is badly distorted by a rapid change in the early stages of the creep effect. In this paper, a new method to obtain the tilt angle of a sample and the creep factor of the Z scanner using only two scanned images with no special tools is proposed. The two scanned images can be obtained by scanning the same area of a sample in two different slow scanning directions. We can then reconstruct a real topographic image based on the scanned image, in which both the creep effect of the Z scanner and the slope effect of the sample have been eliminated. The slope effect of the sample should be eliminated so as to avoid further distortion after removal of the creep effect. The creep effect can be removed from the scanned image using the proposed method, and a real topographic image can subsequently be efficiently reconstructed.     

A small scanning tunnelling microscope with large scan range for biological studies

We have developed a scanning tunnelling microscope specially designed for biological applications presenting some new features: the scanner tube is mounted parallel to the surface of the sample which enables a high resolution optical microscope to be brought close to the sample when working in air or liquids. The maximum scan range is 5×20 μm with a vertical range of 20 μm and the total size of the system does not exceed 10×40 mm. The piezo-sensitivity of the scanner tube versus applied voltage was analysed by interferometry measurements and by using scanning tunnelling microscopes. We found a value for the piezoelectric constant d₁₃ of ?1·71 Å/V at low voltages (under a few volts) going up to ?2 Å/V for higher voltages. Large-scale images of a carbon grid showed a surprisingly good linearity of the scanner tube.     

高精度光谱辐射计测量超低光谱透过率

设计并研制了一种基于光栅双单色仪的高精度全自动单光束光谱辐射计。该仪器主要由高稳定氙灯、带有快门的单光阑屏、石英透镜、中性减光片、紫外光栅双单色仪、光电探测器及电控系统组成,测量光谱范围为200~400 nm, 可以实现10^-6~10^-8量级光谱透过率高精度测量,测量过程由自行编制的计算机软件进行自动控制,能实现全自动单光束测量。给出了该仪器的测量原理、测量方法及数据处理方法。利用该仪器测量了紫外滤光片样品的光谱透过率,分析了测量不确定度。实验结果表明,该仪器测量精度高、速度快、测量合成标准不确定度＜3.16×10^-3,完全满足测量精度要求,可应用于对精度要求高的紫外滤光片光谱透过率的测量。     

Path planning of multi-patched freeform surfaces for laser scanning

In this paper, a new method for scanning a complex surface model with multiple patches is proposed. In scanning of freeform-shaped models, it is difficult to generate a measuring plan by human intuition due to the complexity of the part. The developed method calculates the number of scans, scan direction, and scan path for a stripe-type laser scanner. The user can designate the surface patches that need to be scanned. In generating the scan plan, surface information is first extracted from the CAD model automatically. Other information such as, design knowledge, functionality and machine parameters are provided interactively. Based on this information, the original surface model is sampled in the u, v parameter domain and the sampled points are grouped using the view angle of the laser scanner. The scan direction is determined by calculating the global mean vector of the sampled points that belong to a group. The range of the view angle can be varied to enhance the quality of captured point data. The optical scan paths for each scan direction are calculated by projecting the sampled points onto a 2D plane. The optical constraints are also verified to guarantee the generated scan plan.     

高功率CO_2激光对远场HgCdTe探测器的干扰实验

理论分析和实验研究了高功率CO2激光对远场光导型长波红外HgCdTe探测器的干扰损伤。采用激光辐照探测器的温升理论模型,根据实验参数,讨论了高功率激光对长波红外探测器的损伤机理,计算了温升与辐照时间和功率的关系,并和CO2激光器在距离15km处辐照光导型长波红外HgCdTe探测器的实验结果进行对比分析。实验结果表明,2.5kW连续CO2激光经过大气衰减后在15km处激光功率密度可达0.161W/cm2,计算可知此时会聚到探测器靶面处的功率密度为140W/cm2;靶面处功率密度为20.5W/cm2时,对探测器产生干扰;靶面处功率密度为110W/cm2时,达到损伤,计算此时探测器表面温度已达到Hg析出温度,这一实验现象和理论计算预期结果相吻合。实验结论对研究探测器的激光防护和激光干扰星载探测器技术具有指导意义。     

A digital method for pulse-shape discrimination between particles

Results from experimental and theoretical investigations of a digital technique for pulse-shape discrimination are presented. Pulses from a scintillation (stilbene-based) detector are recorded by a digital oscilloscope and transmitted to a computer for carrying out particle identification. For a stilbene scintillation detector irradiated by neutrons and γ rays, the γ-ray suppression factor is ～0.5 × 10³?10⁴ and the neutron identification efficiency is ～0.70-0.90 over an energy range of ～30–500 keV at a counting rate up to ～10⁵ pulse/s. It is shown that this technique can form the basis for developing a detector unit that comprises a fast ADC and a digital signal processor and provides online identification of particles by scintillation pulse shape.     

Evaluation of a Linear Self-Scanned Photodiode Array Detector for Direct Detection of 6-8 Kev X-Rays

ABSTRACT

The performance of a commercially available 1-dimensional x-ray detector based on a directly bombarded self-scanned photo-diode array has been evaluated for x-rays in the 6-8 KeV range. The detector consists of a linear array of 1024 pixels, each approximately 25 μm wide by 2000 μm tall. Modifications to allow cooling to -55°C, which is required for long x-ray exposures, are described. The signal yield is 0.63 ADC counts/Fe⁵⁵ x-ray, resulting in a detective quantum efficiency greater than 0.5 for doses over a range of 10 to 10⁴ x-rays per pixel per scan when operated at -55°C. The resolution is about 3 pixels (75 μm FWHM) and the response with respect to dose is linear up to 1.5 x 10⁴ x-rays integrated per pixel per scan. There is some non-linearity at doses below about 1000 x-rays/pixel/scan. The detector has very little geometric distortion. The uncorrected uniformity of response of the individual pixels (field flatness) is good to about 2%. However, the variation in responsiveness is stable and a field flatness calibration can be readily used to correct the uniformity of response.