第一台商用激光指纹检测系统

弗吉尼亚州阿灵顿的ALM公司最近建立了第一台商用激光指纹检测系统。这种技术主要靠氩激光感应的荧光来显示，它能识别其它方法难以识别的指纹。     

激光判读指纹技术的改进

一段时间以来，人们知道用氩离子激光器和铜蒸气激光器可以复原传统方法无法解决的指纹。激光照射使残留在指尖接触表面的皮肤油脂发出荧光，这种荧光强度足够大，以致可以从衣服或皮肤表面指纹中提取出来——这是传统方法难以实现的。     

可见波段Ar+激光诱导血红蛋白荧光光谱特性研究

用可见波段、不同波长的Ar^ 激光激发同一浓度血红蛋白溶液产生荧光光谱的研究结果表明，血红蛋白在628nm附近存在一个较强的荧光谱峰，且随激励激光波长的红移其相对光强依次增大，从而解释了临床上用He-Ne激光治疗疗效显著的物理机理。理论研究结果认为该血红蛋白的荧光光谱主要是血红蛋白中存在的卟啉类荧光团的贡献。还利用475．6nm的激光分别激发浓度为1％～7％的血红蛋白溶液，根据所获得的荧光光谱发现，其谱峰位置几乎不随样品浓度的改变而改变，该结果显示了激光与普通光对生物大分子存在明显不同的作用特性。     

离体乳腺正常组织、良性瘤及癌的自体荧光光谱

用４８８ｎｍ氩离子激光作激发光源,对乳腺正常组织、良性瘤及癌的离体组织标本进行了激光诱导组织自体荧光光谱分析。结果表明,三种不同性质的乳腺组织的自体荧光光谱之间有较明显的差异。这些光谱差异对于癌症的光谱诊断研究有一定的参考价值。     

激光晶体荧光谱测试

晶体激光材料的种类繁多,发光所复盖的波段很宽;有些材料的荧光特性又很复杂,需要在不同的条件下测试荧光谱。买来的荧光光度计,往往由于考虑不到这许多复杂的情况而难于应付各种激光晶体荧光谱的测量。许多研究工作者为了得到满意的荧光光谱竟不得不用自己搭配的装置进行测试。我们选用44W光栅单色仪等国产部件组成了一台荧光分光光度计实验装置,用它测量各种激光晶体的荧光光谱,取得了满意的结果。本文结合我们在这台     

基于荧光指纹对指纹遗留时间判定的研究

指纹在法庭科学中具有重要作用，但其遗留时间的判定一直是难以攻克的挑战。本文提出一种基于茚二酮显现法，借助决策树算法的指纹遗留时间判定模型。配制不同浓度的8种氨基酸纯品溶液，并采集10名志愿者指纹，获得遗留时间分别为0、3、7、14、21、30 d的样本。依据样本与茚二酮显现后经绿色波段激光照射，橙黄色滤光器观察下的荧光强度等特征值，构建决策树模型，遗留时间识别准确率达到81%,横向比较支持向量机和多层感知机模型的准确率，确定决策树模型为最优模型。以真实指纹大于等于14 d的数据作为测试集检验该模型，准确率达67%。该方法为指纹遗留时间的判定提供了一定思路。     

油储外围介质的激光诱导荧光光谱分析

石油的长期生成演化在油储外围介质中留下了反映油气存在的“指示物”。对这些介质取样的激光诱导荧光光谱分析研究表明,激光荧光光谱可以揭示油砂、钻井岩心、浅层水、土壤等油气藏外围介质中所含的油气“指示物”——芳烃,且不同激发波长所对应的介质取样荧光光谱反映着不同的油气芳烃组份。这对于用光谱分析法开展大面积找油具有指导意义。     

He-Ne激光照射人血液对荧光光谱影响研究

取离体健康人血液,用2mw、6mw、8mW、10mW不同功率的低强度He-Ne激光照射30min后,再以407nm和532nm作为激发光测量了全血的荧光光谱。发现对于不同功率的He-Ne激光照射过的血液,荧光峰值与照射前有明显的变化。应用光谱基础知识对实验结果进行了分析和讨论。     

掺Er石英光纤的1560nm光纤激光和超荧光

用Ar离子514.5nm激光泵浦掺Er石英光纤产生了1560nm的激光和超荧光输出。激光最大输出功率5.4mW,斜率效率9.5％;超荧光最大输出功率1.6mW,并观察到光纤超荧光的谱窄化现象。     

飞秒激光成丝诱导荧光空间分布特性研究进展

光丝内部的超高钳制光强可诱导大气中的原子、分子等发生隧道电离或多光子电离,并辐射指纹荧光谱。得益于其在复杂大气环境中能够远距离传输的特点,飞秒激光成丝在大气远程探测方面具有广阔的应用前景。光丝诱导物质荧光的空间分布特性与成丝过程中激光、等离子体等参数密切相关,对于理解光丝内物理过程及调控光丝、提升远程探测信噪比等具有重要意义。综述了光丝诱导荧光在侧向、背向及前向三个重要方位的空间分布的研究进展,详细讨论了基于侧向分布表征光丝内光强及等离子体分布的方法,以及实验条件对荧光空间分布的影响,并对放大自发辐射现象及前向、背向远场空间分布的研究进展进行了介绍。最后对飞秒激光成丝诱导荧光空间分布的研究趋势进行了展望。     

非接触式指纹采集与识别的研究

为了构建一个结构紧凑、实时、高效、小型的指纹采集识别系统,提出了非接触式光学采集方法.即采用激光或非相干光源,利用激光透射、扫描和非相干光照射,通过超半球浸没透镜和双胶合透镜等组合的光学系统,运用光学非接触式方法实现完整、清晰的指纹图像的采集,这种方法有效地避免了接触式所造成的指纹的旋转、扭曲和变形,提高了采集图像的质量.从而为利用空间光调制器实现指纹的实时傅里叶相关识别提供了有效的保证.     

细菌视紫红质膜的光抽运质子(电荷) 转移的光学动态吸收特性研究

用自行设计的“连续抽运-探测光 脉冲抽运光”的实验系统,在不同波长的连续和脉冲光作用下,研究了细菌视紫红质(BR)膜的瞬态光吸收性质,并着重以632.8nm的激光为连续抽运-探测光研究了BR的质子电荷光循环过程中,各能态的光吸收动力学过程及其瞬态光吸收特性与连续抽运-探测光强和脉冲抽运光强的关系     

Improving the performance of power GaN-based thin-film flip-chip LEDs through a twofold roughened surface

To further enhance the light extraction efficiency of GaN-based thin-film flip-chip light-emitting diodes (TFFC-LEDs), a surface roughening technique using KrF excimer laser ablation and chemical wet etching is demonstrated. Both optical ray-tracing simulations and experimental results of the light emission characteristics are presented and discussed. With the proposed twofold surface texturing scheme with circular protrusions superimposed by hexagonal cones, the angular randomization of photons at the emission surface was maximized, enhancements in light output power of 13.08% (12.81%) and wall-plug efficiency of 2.87% (2.25%) at 350 mA (700 mA) compared to those of a TFFC-LED without surface texturing were obtained.     

Contact and proximity lithography using 193 nm Excimer laser in Mask Aligner

In this paper we describe the use of an Excimer laser for full-field lithography in a Mask Aligner. The DUV light from the Excimer laser is homogenized by using micro lens based optical integrators instead of a macro lens array. A simulation of the intensity distribution for 5 μm squares was performed to visualize the diffraction effects and to show the potential of 193 nm illumination. It is demonstrated that compared to the conventional homogenization optics the MO Exposure Optics further improves the illumination uniformity, calculated as 1.8% for MO Exposure Optics and 2.9% for the A-Optics. Moreover the improved optical setup allows a modification of the angular spectrum by using exchangeable illumination filter plates (IFP). Compared to the A-Optics the main improvement effect of MO Exposure Optics is detectable in the patterning of layouts containing critical dimension from 8 μm down to 2 μm.     

Means and verification of broadcast technology applied to laser transmission on horizontal link

At present, there has been great progress in the field of the point-to-point laser communication technology, in other words, the traditional laser communication technology has been advanced day by day. Furthermore, in order to search for an effective means of achieving localized laser broadcasting communication within a limited range, an effective method of horizontal link laser broadcasting communication is presented, and the corresponding verifiable broadcast communication system is designed. In addition, the laser broadcasting is systematically studied by one physical model built at the optimal distribution of optical power. First of all, the theoretical model of laser beam expansion and the theoretical model of parallel light curtain are made comparisons and analyzed from the angle of attenuation of optical power, and the optical power loss model of the parallel light curtain is established as a result. Secondly, combined with the theory of optical imaging transformation based on Gaussian beam, the field distribution of far field of parallel light curtain is simulated by one leading optical and illumination design software and the relation between the filed distribution of far field of light curtain and the distance of transmission is revealed. Finally, the superiority and feasibility of the parallel light curtain theory model are verified by field communication experiments in different information channels.     

水平链路激光广播技术的功率传输方法与验证

当前传统点对点激光通信技术已经得到了长足进步,为了探索在有限范围内实现局域激光广播的有效手段,提出了一种适用于短距离水平链路激光广播的有效方法,设计了相应的验证性广播通信系统,并在光功率最优分配的角度上对激光广播进行了系统建模研究。首先,从光功率衰减的角度对激光扩束理论模型和平行光幕理论模型进行了分析和对比,揭示了平行光幕通信模型的光功率损失模型;其次,结合高斯光束光学成像变换理论模拟了平行光幕的远场场强分布情况,通过一个领先的光学和照明设计软件,揭示了光幕远场分布与传输距离的关系;最后,通过在不同信道环境下的野外通信实验验证了平行光幕理论模型的优越性与可行性。     

Low-coherence interferometric fiber sensor with improved resolution using stepper motor assisted optical ruler

Low-coherence interferometric sensing is typically used to detect phase changes without simultaneous optical ruler calibration in order to by-pass light intensity fluctuations and the periodic nature of the interferometric signal. An interferogram from a two-staged optical low-coherence Mach–Zehnder interferometer is proposed to double the sensitivity improvement for fiber strain sensing. A 1310-nm wavelength distributed feedback laser implemented in an optical ruler achieved 655-nm resolved characterization from its high-coherence interferogram, which could further be enhanced to an average of 18.9 nm using a stepper motor assisted optical ruler. A 2.7-nε high strain resolution was then demonstrated on a 3-m long fiber sensing arm in a Mach–Zehnder interferometer. The relative movement distances between the interferograms were utilized to experimentally show the strain and force sensitivity as 6.8 μm/με and 8.5 μm/mN, respectively.     

一种功率可调的稳定激光光源的实现方法

在光纤通信系统测试中,波长为850 nm、 1310 nm、1490 nm、1550 nm和1625 nm 等的红外激光光源作为信号源具有广泛的应用。该光源需要 具有稳定的输出光功率。通常采用含有衰减片的光 衰减器对其输出光功率进行调节以满足不同场合的测 试与校准需求。通过分析激光器输出功率与 驱动电流的特征曲线,提出了一种在电路上采用压控电 流的方法,实现了稳定光源的输出光功率步进可调(调 节范围为30 dB)。该方法可有效减少光衰减器的使用,缩减测 试系统的仪器数量,提高测试效率,降低测试成本。     

Metal-catalyzed synthesis of ultralong tin dioxide nanobelts: Electrical and optical properties with oxygen vacancy-related orange emission

Tin dioxide (SnO₂) ultralong nanobelts were fabricated on silicon substrate by metal catalyzed Chemical Vapor Deposition (CVD) approach. An optical bandgap of 3.66 eV was calculated by optical absorbance data. Three Raman active modes peaks were observed at 474.4, 633 and 774.4 cm⁻¹. Room temperature photoluminescence (PL) exhibited an orange emission at 600 nm. A vapor–liquid–solid (VLS) process based growth mechanism for the formation of SnO₂ nanobelts was proposed and discussed briefly. Electrical transport characteristics of nanobelts were studied in dark and under ultraviolet (UV) laser. The fabricated device exhibited high photo-response properties under UV light, indicating their potential application as photo-switches and UV detectors.     

Stable and wavelength-tunable RSOA- and SOA-based fiber ring laser

In this work, we propose and experimentally investigate a wavelength-tunable fiber ring laser architecture by using the reflective semiconductor optical amplifier (RSOA) and semiconductor optical amplifier (SOA). Here, the wavelength tuning range from 1538.03 to 1561.91 nm can be obtained. The measured output power and optical signal to noise ratio (OSNRs) of the proposed fiber laser are between -0.8 and -2.5 dBm and 59.1 and 61.0 dB/0.06 nm, respectively. The power and wavelength stabilities of the proposed laser are also studied. In addition, the proposed laser can be directly modulated at 2.5 Gbit/s quadrature phase shift keying-orthogonal frequency-division multiplexing (QPSK-OFDM) signal and 20–50 km single-mode fiber (SMF) transmissions are achieved within the forward error correction (FEC) limit without dispersion compensation. It could be a cost-effective and promising candidate for the standard-reach and extended-reach wavelength division multiplexed passive optical network (WDM-PON).