有机分子束外延技术与研究进展

本介绍了超高真空分子束外延生长有机薄膜的技术及基研究进展,讨论了外延材料的纯化过程和杂质对外延薄膜的影响;从理论和实验观点评论了薄膜的生长性质和膜的有序结构。超高真空有机分子束外延技术是一种多用途的高技术,可以生长有机、无机、有机／无机混和的薄膜结构。这种薄膜结构是示来光学和电子器件有希望应用的新一类工程材料。     

有机分子束外延技术与研究进展

本文介绍了超高真空分子束外延生长有机薄膜的技术及其研究进展 ,讨论了外延材料的纯化过程和杂质对外延薄膜结构的影响 ;从理论和实验观点评论了薄膜的生长性质和膜的有序结构。超高真空有机分子束外延技术是一种多用途的高技术 ,可以生长有机、无机、有机 /无机混和的薄膜结构。这种薄膜结构是未来光学和电子器件有希望应用的新一类工程材料。     

分子电子学与离化团束（ICB）薄膜新技术

本文介绍了新的交叉学科──分子电子学的研究范围、目标和进展，介绍了有机材料传统的形膜技术（ＬＢ膜技术）及其新进展．重点介绍了新近发展起来的ＩＣＢ薄膜淀积技术的基本原理和特点，总结了用ＩＣＢ 淀积技术制备有机薄膜取得的成效，展望了ＩＣＢ淀积技术在有机分子材料及电子学领域中的发展方向和应用前景．     

通过具有偏振选择性的紫外/红外混频超快光谱探测有机光电薄膜中的相对分子取向

分子堆积模式是决定电子/能量转移过程的关键因素,影响有机薄膜器件的光电特性. 本文通过具有偏振选择性的紫外/红外混频超快光谱研究了7-(二乙氨基)香豆素-3-羧酸和苝两种有机分子的薄膜. 并利用分子间能量/电子转移引起的信号各向异性变化来计算供体的电子跃迁偶极矩与受体的振动跃迁偶极矩之间的夹角,从而得出两个相邻分子之间的相对取向. 用这种方法测得7-(二乙氨基)香豆素-3-羧酸薄膜的相对取向角为53.4o,接近其单晶结构的60o,苝薄膜的相对取向角为6.2o,也接近其单晶结构的-0.2o. 除了实验中的不确定性,这种方法确定的角度与单晶的角度之间的微小差异还可能源于薄膜样品是多晶的,且其中一些分子是无定形的.     

具有叠层超薄膜结构的高性能有机晶体管氨气传感器

研究了基于给-受体共轭聚合物双(2-氧代二氢吲哚-3-亚基)-苯并二呋喃-二酮和联噻吩(PBIBDF-BT)超薄膜叠层晶体管的电学性能及氨气传感特性。使用相分离方法以及转移-刻蚀步骤制备了不同堆叠层数的PBIBDF-BT超薄膜。系统地研究了PBIBDF-BT超薄膜堆叠层数与器件性能的关系。实验结果表明,单层PBIBDF-BT超薄膜器件对氨气具有良好的传感性能,电学性能较差。超薄膜叠层能够有效提高传感器的电学性能,随着超薄膜叠层数量的增加,器件迁移率不断上升;超薄膜层数增加为3层及更多时迁移率上升趋势变缓,迁移率最大值为0.58 cm~2·V~(-1)·s~(-1)。超薄膜叠层器件氨气传感性能在层数为2层后呈现下降趋势。通过PBIBDF-BT超薄膜叠层方法,制备出在1.0×10~(-5)氨气环境下,迁移率为0.23 cm~2·V~(-1)·s~(-1)、源漏电流变化百分比为90.7%、性能良好的OFET氨气传感器。     

具有叠层超薄膜结构的高性能有机晶体管氨气传感器EI北大核心CSCD

研究了基于给-受体共轭聚合物双(2-氧代二氢吲哚-3-亚基)-苯并二呋喃-二酮和联噻吩(PBIBDF-BT)超薄膜叠层晶体管的电学性能及氨气传感特性。使用相分离方法以及转移-刻蚀步骤制备了不同堆叠层数的PBIBDF-BT超薄膜。系统地研究了PBIBDF-BT超薄膜堆叠层数与器件性能的关系。实验结果表明,单层PBIBDF-BT超薄膜器件对氨气具有良好的传感性能,电学性能较差。超薄膜叠层能够有效提高传感器的电学性能,随着超薄膜叠层数量的增加,器件迁移率不断上升;超薄膜层数增加为3层及更多时迁移率上升趋势变缓,迁移率最大值为0.58 cm^(2)·V^(-1)·s^(-1)。超薄膜叠层器件氨气传感性能在层数为2层后呈现下降趋势。通过PBIBDF-BT超薄膜叠层方法,制备出在1.0×10^(-5)氨气环境下,迁移率为0.23 cm^(2)·V^(-1)·s^(-1)、源漏电流变化百分比为90.7%、性能良好的OFET氨气传感器。     

基于差分反射光谱的真空环境有机薄膜生长在线监测方法

有机薄膜器件是微电子和光电子领域的重点研究方向。薄膜制备过程的在线监测作为研究成膜机理和优化工艺参数最直接的测量手段,对薄膜器件的高质量制备具有重要意义。为实现真空环境有机薄膜制备过程的实时在线监测,提出了一种基于差分反射光谱术的高精度测量方法。采用离轴抛物面反射镜、光学平板和光纤等基本光学元器件构建紧凑型光路系统,运用差分算法分析光谱信号,具有较高的测量性能。测试了不同实验环境下光谱信号的波动,得出在控温条件下,系统的长时间测量重复性优于2‰。还研究了并五苯分子通过分子束外延制膜法在Au基底成膜初始阶段的生长过程。通过与膜厚仪和原子力显微镜测试结果比对,光谱信号精确反映出超薄膜在生长中引起的细微光学演变,其测量精度优于亚单分子层。实验结果表明,该差分反射光谱测量系统具有宽光谱(300～820 nm)、高稳定性(重复性优于2×10-3)、高测量精度(亚单分子层)等特点,并有效地抑制了光路装配误差、光学器件缺陷和环境干扰等对光信号的影响,作为一种高精度表面表征方法,适合于薄膜制备过程的实时在线监测。     

LB膜的物理性能与应用

ＬＢ膜是一种分子有序排列的有机超薄膜，这种膜不仅是薄膜科学研究的重要内容，也是物理学，电子学，生物学等多种学科相互交叉渗透的新的研究领域，为近年来国内外研究的热点之一，本文对ＬＢ膜的发展历史，基本要领组装制备，物理特性及栽些应用作了全面扼要的介绍。     

单壁碳纳米管太赫兹超表面窄带吸收及其传感特性

由于碳纳米管具有优异的电学和光学特性,因此在光电子学领域具有广泛的应用前景.本文使用真空抽滤法,将单壁碳纳米管粉末分散液通过真空过滤的方式,制备了一种各向同性的单壁碳纳米管薄膜;进而提取了薄膜在0.4—2.0 THz范围内介电参数,并设计了一种基于单壁碳纳米管薄膜的新型太赫兹超表面窄带吸收器,这种超表面吸收器是由方形与工字形狭缝谐振器构成.实验和仿真结果表明,提出的太赫兹超表面吸收器在0.65,0.85,1.16和1.31 THz处存在4个明显的共振吸收峰,实现了最高可达90%的完美吸收.利用多重反射干涉理论阐明了这种多频带新型太赫兹超表面的吸收机制.通过在超表面器件表面覆盖具有不同折射率的介质层,深入研究了超表面作为折射率传感器的传感性能.研究结果表明,这种新型超表面吸收器用于折射率传感具有较高的灵敏度,为进一步开发新型碳基太赫兹超表面吸收器提供了新的思路和方案.     

有机薄膜电致发光器件结构与发光特性的研究

从有机电致发光薄膜的发光机理出发，通过以Ａｌｑ薄膜器件、ＰＶＫ为空穴传输层和Ａｌｑ为发光层的双层 及ＰＶＫ掺荧光材料Ｐｅｒｙｌｅｎｅ的双层薄膜器件的研制，从器件的电致姚谱、电流密度－电压特性、亮度－电压特性的曲线的测试结果，计算分析了器件的流明效率、量子效率，并对有机薄膜电致发光器件的结构与发光特性之间的关系进行研究，利用能级理论分析了器件的姚特性随器件的结构不同所具有的规律。实验表明，加入ＰＶＫ     

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.