新型大尺寸透中红外氧氟化物光学玻璃研究

红外光学玻璃是很多重要军、民用系统的关键窗口材料之一,但其高性能化、大尺寸化制备面临重要挑战。针对氟化物玻璃易挥发、抗析晶性能较差等特点,通过向含TeO2的氟铝酸盐玻璃中引入碱土金属氧化物BaO,显著降低了玻璃在熔制中的挥发,同时提高了玻璃的热稳定性。通过Raman光谱的分析,发现BaO的增加抑制了富TeO2玻璃分相,有利于碲酸盐玻璃与氟铝酸盐玻璃之间的融合,促进了玻璃网络结构的稳定。所得的氧氟化物红外光学玻璃有优异的红外透射性能,和氟化钙晶体性能对比,显示出低成本优势和更强的环境适应性。     

新型红外氧氟玻璃及其雷达隐身技术

红外玻璃是很多重要军用系统的关键窗口材料之一,红外玻璃的高性能、大尺寸化制备面临重要挑战,同时红外技术和光电对抗技术的发展对红外窗口的雷达隐身性能也提出了很高的要求。阐述了新型红外玻璃的设计思想,基于此发展了一种新型的中红外光学玻璃—氟镓酸盐(FGa)玻璃,并以FGa玻璃为基质,成功研制出新型具有雷达隐身功能的中红外光功能材料。     

红外导引头整流罩技术研究

从材料选择和整流罩设计两方面,介绍了如何解决高速红外导引头整流罩问题.针对高速红外成像导引头使用环境的要求,分析了整流罩材料选择应考虑的因素.通过比较材料的透过率、硬度、抗弯强度和热膨胀等性能参数,得出尖晶石是较理想的高速导弹整流罩材料,其机械性能和光学性能良好,易于制备,并已取得成功应用;红外玻璃特别适合大尺寸和复杂形状制备.为了减小整流罩气动加热效应,分析了解决气动加热问题的途径,提出可通过镀金刚石膜、信号处理、共形设计等技术来减小影响,并简要介绍共形整流罩设计原理和制造.     

新型远红外Ge-Te-Se-Sn硫系玻璃的热学与光学性质研究

采用熔融淬冷法制备了新型远红外Te基硫系玻璃Ge20-xTe65 Se15 Snx(x=0,2,4).在Ge-Te-Se玻璃的基础上,通过引入重金属Sn,研究其对玻璃组成、结构和性能的影响.测试了样品的中红外热成像、X射线衍射(XRD)图谱、差热分析曲线(DSC)、可见/近红外吸收光谱、红外透射光谱.利用经典的Tauc...     

机载光电设备红外8～12μm光学窗口技术研究

基于机载光电设备红外窗口的性能要求，对几种8～12μm波段红外材料的性能进行了比较，分析ZnS材料作为长波红外窗口的优越性，并对两种不同工艺制备的ZnS的光学、力学和热性能进行了分析和比较，对以ZnS为基底的窗口材料的镀膜选择进行了分析．介绍了一种红外窗口厚度的确定方法，并对不同厚度及镀膜前后的ZnS样品进行了透过率的测试．     

表界面调控米级二维单晶原子制造

随着芯片尺寸不断缩小,短沟道效应、热效应日趋显著.开发全新的量子材料体系以实现高性能芯片器件应用已成为当前科技发展的迫切需求.二维材料作为一类重要的量子材料,其天然具备原子层厚度和平面结构,能够有效克服短沟道效应并兼容当代微纳加工工艺,非常有望应用于新一代高性能器件方向.与硅基芯片发展类似,二维材料芯片级器件应用必须基于高质量、大尺寸的二维单晶材料制造.然而,由于二维材料的表界面特性,现有体单晶制备技术不能完全适用于单原子层结构的二维单晶制造.因此,亟需发展新的制备策略以实现大尺寸、高质量的二维单晶原子制造.有鉴于此,本文重点综述表界面调控二维单晶大尺寸制备技术发展现状,总结梳理了米级二维单晶原子制造过程中的3个关键调控方向,即单畴生长调控、单晶衬底制备和多畴取向控制.最后,系统展望了大尺寸二维单晶在未来规模化芯片器件方向的潜在应用前景.     

RF-PECVD法制备大面积类金刚石薄膜性能的研究

采用RF-PECVD法在锗、硅红外光学窗口上制备了大面积(基底直径φ=150～250mm)类金刚石薄膜.采用拉曼光谱分析了大面积DLC膜的结构组成,对RF-PECVD法制备的大面积DLC膜的均匀性、红外光学性能、机械力学性能以及其抗恶劣环境的能力进行了检测和分析.膜层厚度均匀性在3%以内.锗、硅红外窗口双面镀制DLC膜后,极值透过率分别达92%和96%以上,可显著提高红外光学窗口的显微硬度.膜层具有极强的抗盐雾、耐海水腐蚀和抗摩擦的能力.     

远红外窗口聚乙烯性能研究

采用压缩模塑法制备了聚乙烯远红外窗口，对红外窗口材料的成型条件和性能进行了测试分析。结果表明，成型温度为150℃，样品的成型压力对红外透过率没有影响，窗口材料的红外透过率随厚度的增加而减小，最后选定样品厚度为2mm，在15μm以后具有较好的透过率。抗腐蚀性能测试结果表明，材料耐强酸、强碱及部分有机溶剂。     

PbI2对远红外Te基硫系玻璃光学性能的影响

用传统的熔融淬冷法制备了一系列新型Ge-Te-PbI₂硫系玻璃,并且讨论了玻璃的形成区域. 利用X射线衍射(XRD)、差热分析(DTA)、可见/近红外吸收光谱、红外透过光谱等技术,研究重金属卤化物PbI₂对Ge-Te硫系玻璃组成、结构和性能的影响. 利用Tauc方程计算了样品的直接和间接光学带隙,根据金属标准和能量带隙理论讨论了玻璃光学带隙与组分变化的关系. 结果表明:PbI₂的引入,提高了Te玻璃的形成能力,而且玻璃的热稳定性良好;随着PbI₂含量的增加,玻璃的密度和折射率均增大,光学带隙减小,短波吸收截止边发生红移,玻璃的红外截止波长基本不变,达到了25 μm. 该系列玻璃可用于制备远红外长波波导器件. 关键词： Te基玻璃 2')" href="#">PbI₂ 光学带隙 红外光谱     

Ge-Se基硫系玻璃在通信波段的三阶非线性与光谱特性研究

在Ge-Se二元体系中引入相同摩尔比的Ga, Sn, Sb, Te四种元素, 使用熔融淬冷法制备了一系列硫系玻璃. 利用吸收光谱获得了不同元素引入下硫系玻璃能带结构的变化, 并结合拉曼光谱详细研究了产生光学特性变化的微观表征. 使用Z扫描方法测试了各个硫系玻璃样品在1550 nm波长下的三阶非线性参数, 发现加入Sn的玻璃的三阶非线性折射率n₂最大, 达到了6.36×10^-17 m²/W, 且其品质因子大于23, 表明Sn引入能够增强硫系玻璃在通信波段的三阶非线性, 这一研究结果为以后的高性能红外器件的设计及制备提供了一种环保且性能优良的候选材料.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Characterization of PolyA and PolyC mismatches by Raman spectroscopy

A.C mismatches are studied by Raman spectral characterization of PolyA, PolyC, and their equimolar complex in solution of 0.14 mol/L Na ,pH7.0.Experimental results show that A·C mismatches occur to be A/B (mainly A) conformers, and unlike Watson-Crick base pairing, this kind of mismatches is stabilized by only one hydrogen bond involving cytosine N4H2 and adenine N7.The formation of A·C complex makes the base stacking interactions much stronger, and conformation of the backbone more ordered, which leads to obvious Raman hypochromic effect with some shifts in corresponding bands.     

Improvement of four-wave mixing-based wavelength conversion efficiency in dispersion shifted fiber by 40-GHz clock pumping

40-GHz clock modulated signal as a pump to improve the efficiency of four-wave mixing (FWM)-based wavelength conversion in a 26.5-km dispersion shifted fiber (DSF) is investigated. The experimental results demonstrate that the conjugated FWM component has higher intensity with the clock pumping than that with the continuous-wave (CW) light pumping. The improvement of FWM-based wavelength conversion efficiency is negligible when the pump power is less than Brillouin threshold. But when the pump power is greater than Brillouin threshold, the improvement becomes significant and increases with the increment of pump power. The improvement can increase up to 9 dB if pump power reaches 17 dBm.     

Multi-pulse operation of a Kerr-lens mode-locked femtosecond laser

Our experimental results show that the presence of a proper amount of negative group velocity dispersion is essential to multi-pulse operation of a Kerr-lens mode-locked femtosecond laser. We demonstrate that the pulse separations and the number of pulses contained within a cavity round trip are strongly dependent on the initial perturbations. The results allow us to get a better understanding on the influences of the convoluted self-phase modulation and intra-cavity dispersions on the stable multi-pulse oscillation in a Kerr-lens mode-locked femtosecond laser.     

Propagation of Helmholtz-Gauss beams in weak turbulent atmosphere

Based on the Rytov approximation of light propagation in weak turbulent atmosphere,the closed-form expressions of field and average irradiance of each one of the four fundamental families of Helmholtz-Gauss (HzG)beams:cosine-Gauss beams,stationary Mathieu-Gauss beams,stationary parabolic-Gauss beams,and Bessel-Gauss beams,which are propagating in weak turbulent atmosphere,are obtained.The results show that the field and average irradiance can be written as the product of four factors:complex amplitude depending on the z-coordinate only,a Ganssian beam.a factor of complex phase perturbation induced by atmospheric turbulence,and a complex scaled version of the transverse shape of the non-diffracting beam.The effect of weak atmospheric turbulence on irradiance distribution of the HzG beam can be ignored.     

An effective method for reducing speckle noise in digital holography

An effective method for reducing the speckle noise in digital holography is proposed in this paper.Different from the methods based on classical filtering technique,it utilizes the multiple holograms which are generated by rotating the illuminating light continuously.The intensity images reconstructed by a series of holograms generated by rotating the illuminating light possess different speckle patterns.Hence by properly averaging the reconstructed intensity fields,the speckle noises can be reduced greatly.Experimental results show that the proposed method is simple and effective to reduce speckle noise in digital holography.     

Influence of purity of HfO2 on reflectance of ultraviolet multilayer

The impurities in two kinds of HfO2 materials and in their corresponding single layer thin films were determined through glow discharge mass spectrum technology and secondary ion mass spectrometry(SIMS) equipment respectively.It was found that ZrO2 was the main impurity in the two kinds of HfO2 either in the original HfO2 materials or in the electron beam deposited films.In addition,the difference of Zr content in the two kinds of HfO2 single laver films was much laxger than that of the other impurities such as Ti and Fe.which showed that it was just ZrO2 that made the difference between the optical performance of the film products including the two kinds of HfO2.With these two kinds of HfO2 and the same kind of SiO2.we deposited HfO2/SiO2 multilayer reflective coatings at the wavelength of 266 nm.Experimental results showed that the reflectances of these two mirrors were about 99.85% and 99.15% respectively,which agreed well with the designed results what were based on the optical constants obtained from the corresponding single layer thin films.     

Speech enhancement by array crosstalk resistant ANC and spectrum subtraction

Microphone array-based speech enhancement has great importance for speech communications and speech recognition. To reduce the aperture of the microphone array and to increase the effect of the speech enhancement will greatly broaden the application areas of the microphone array. An array crosstalk resistant adaptive noise cancellation method is therefore presented. And then an improved spectral subtraction algorithm is further cascaded to obtain better enhancement results. Theoretic analysis and experiments indicate that the proposed scheme needs only a very small microphone array while it simultaneously achieves a higher SNR improvement. Besides, the proposed scheme can be used in many noisy environments and is easy for real-time implementation.