量子点液晶显示背光技术

量子点材料兼具极高的色纯度、发光颜色可调以及的荧光量子产率高等特点,已成为显示领域中的明星材料,在提升显示器件的色域方面具有巨大潜力。基于量子点材料的液晶显示背光技术是目前量子点材料在显示器件中的主流应用方向,引起了学术界和工业界的广泛关注。本文将综述量子点液晶显示背光技术的研究进展,主要包括量子点材料的选择、背光结构的应用以及材料复合与封装技术的发展现状,重点介绍了目前产业界广泛关注的量子点光学膜技术,特别是国内自主知识产权的低成本钙钛矿量子点光学膜技术,由于其具备广色域(124%NTSC)、易加工、低成本等特点,已成为具有成长潜力的技术路线。     

GaN基白光LED的研制与特性

本文报导了通过低压金属有机物化学气相沉积(MOCVD)的InGaN/GaN量子阱蓝光发光二极管(LED)与钇铝石榴石(YAG)荧光粉结合而得的白光发光二极管(W-LED).在室温、正向电流20mA时,W-LED轴向亮度为170mcd,显色指数(CRI)达到82,色温(CCT)为7448K,CIE色坐标是(0.296,0.316),接近纯白色(0.33,0.33).随着注入电流的增强,测量并探讨了白光LED的发射光谱与发光强度的变化.     

碳点-纤维素复合红色发光材料制备及性能EI北大核心CSCD

白光LED器件作为新一代绿色固态照明光源,已广泛应用于照明、液晶背光等领域,也与智能照明、物联网技术等高新科技产业密切相关。常用的蓝光芯片复合黄光YAG∶Ce^(3+)(Y 3Al 5O 12∶Ce^(3+))荧光粉的白光器件由于缺少红色光谱的成分,导致器件光谱较窄,显色指数较低,色温偏高。因此,红色荧光粉对改善白光LED的光色品质起到了重要作用。本文首先制备了红色碳点(量子效率28%),通过把红色碳点与纤维素复合,制备了红色荧光粉(量子效率为18%)。该红色荧光粉与黄光YAG∶Ce^(3+)荧光粉混合,封装得到暖白光。结果表明,相较于只有黄光YAG∶Ce^(3+)荧光粉封装的LED,红色荧光粉掺杂之后,在460 nm蓝光芯片的激发下,白光LED的色坐标由(0.30,0.33)变化到(0.33,0.35),色温从7396 K下降到5714 K,显色指数从78.2升高到82.9,实现了由色温高、显示指数低的冷白光向色温低、显色指数高的暖白光的调节。     

光学仪器 X射线、紫外线及其仪器

O434 2006043774针孔点背光技术实验=Experi ments of point-projectionbacklighting using pinholes[刊,中]/江少恩(中物院激光聚变研究中心.四川,绵阳(621900)) ,黄冀翔…∥光子学报.—2006 ,35(2) .—290-293在“星光Ⅱ”装置上进行针孔点背光技术的演示实验。利用激光辐照φ50μm的小孔产生的堵孔效应使X光的脉宽缩短,起到类似于短脉冲点背光源的作用。另外利用成像方法,实验演示了由面背光方式获得点背光技术,称之为点针孔背光技术。实验结果表明,结合堵孔效应和点背光方式,能获得与点背光同样的结果,这样可以避开点背光对激光器较为…     

碳点-纤维素复合红色发光材料制备及性能

白光LED器件作为新一代绿色固态照明光源,已广泛应用于照明、液晶背光等领域,也与智能照明、物联网技术等高新科技产业密切相关。常用的蓝光芯片复合黄光YAG∶Ce~(3+)(Y_3Al_5O_(12)∶Ce~(3+))荧光粉的白光器件由于缺少红色光谱的成分,导致器件光谱较窄,显色指数较低,色温偏高。因此,红色荧光粉对改善白光LED的光色品质起到了重要作用。本文首先制备了红色碳点(量子效率28%),通过把红色碳点与纤维素复合,制备了红色荧光粉(量子效率为18%)。该红色荧光粉与黄光YAG∶Ce~(3+)荧光粉混合,封装得到暖白光。结果表明,相较于只有黄光YAG∶Ce~(3+)荧光粉封装的LED,红色荧光粉掺杂之后,在460 nm蓝光芯片的激发下,白光LED的色坐标由(0.30,0.33)变化到(0.33,0.35),色温从7 396 K下降到5 714 K,显色指数从78.2升高到82.9,实现了由色温高、显示指数低的冷白光向色温低、显色指数高的暖白光的调节。     

基于CuInS2/ZnS核壳结构量子点的高光效暖白光LED

采用逐步热注射法合成了用于白光LED的CuInS₂/ZnS(CIS/ZnS)核壳结构量子点.通过调整Cu/In的比率, 在CuInS₂(CIS)量子点的基础上, 合成了发射波长在570~650 nm之间可调的CIS/ZnS量子点.与CIS量子点的低量子产率相比, 具有核壳结构的CIS/ZnS量子点的量子产率达到了78%.通过在黄光荧光粉YAG :Ce³⁺表面旋涂CIS/ZnS量子点的方式制备了暖白光LED器件.在工作电流为10 mA时, 暖白光LED的发光效率达到了244.58 lm/W.由于CIS/ZnS量子点的加入, 所制备的白光LED器件的显色指数达到86.7且发光颜色向暖色调发生了转移, 相应的色坐标为(0.340 6, 0.369 0).     

量子点背光技术的研究进展

量子点材料因具有发光波长可调,色度纯,量子效率高等优异特性而受到广泛关注,在光致发光高色彩显示方面有着巨大的应用潜力。本文综述了量子点背光技术的研究进展,主要对比了QDs On-Chip、QDs On-Surface及QDs On-Edge 3种量子点背光主流技术的基本原理及结构,并分析了它们在液晶显示领域的应用,未来前景及面临的挑战;然后介绍了几种新型的量子点背光技术,并对两种量子点背光新技术进行重点说明:一种是采用低温注塑成型工艺将量子点与高分子材料均匀混合为一体,用于制备直下式背光的量子点体散射型结构扩散板;另一种新技术是采用丝网印刷或喷墨打印工艺将量子点转印至导光板表面,形成应用于侧入式背光的量子点网点微结构导光板。这两种背光都具有制备工艺简单、成本低、生产效率高等特点,对高色域液晶显示的研究及发展意义深远。     

CdSeS量子点的光学非线性特性

以脉冲宽度为35 ps,基频为1064 nm的Nd:YAG锁模激光器二倍频532 nm的激光作激发,利用Z-扫描技术研究了CdSeS量子点的光学非线件特性.实验结果表明CdSeS量子点在532 nm光激发下具有很大的非线性吸收效应,该吸收效应来自于光学三阶效应引起的双光子吸收.在不同的入射光强下观测了CdSeS量子点的Z-扫描曲线,实验表明,CdSeS具有大的非线性折射率1.9×10-8esu和大的双光子吸收截面25283 GM,比现在使用的ZnS量子点高出近2个数量级.     

水热法合成Ag-In-Zn-S绿色四元量子点 及其荧光性能研究

以无机金属盐为原料、谷胱甘肽(GSH)和柠檬酸钠(SC)为配体,通过水热法制备了AIZS量子点.系统研究了pH值、Ag/In比例、Ag/Zn比例对AIZS量子点的合成及其荧光性能的影响,并通过X射线衍射仪、透射电子显微镜、红外光谱、紫外-可见吸收光谱以及光致发光光谱分别对样品的结构、形貌和荧光性能进行了表征.实验结果表明,通过水热法可以制备出具有优异荧光性能的AIZS四元绿色量子点.随着pH值的增加(pH值=7～9),配体GSH和SC有效地钝化了AIZS量子点的表面缺陷,显著提高了其荧光强度.当Ag/In比例为1∶1～1∶11范围内,量子点发光峰的中心位置覆盖632.1 nm～588.9 nm;当Ag/In=1∶7时,AIZS量子点的量子产率高达27.3%.此外,随着Ag/Zn比例从1∶0.5减小至1∶3.0,量子点的合金化效应逐渐增强,使其发光峰位从604.1 nm蓝移至581.5 nm;当Ag/Zn=1∶1.5时,AIZS量子点的发光强度达到最大值,量子产率进一步提升至35.3%,说明Zn~(2+)的引入具有稳定AIZS量子点的晶格以及抑制非辐射复合效应的作用,从而显著提高量子点的荧光性能.在200 mA的电流驱动下,AIZS量子点基白光LED的光效可达60.8 lm/W,显色指数高达80.1,色坐标为(0.29,0.35),说明AIZS四元量子点在照明领域具有良好的应用前景.     

针孔点背光技术实验

在“星光Ⅱ”装置上进行针孔点背光技术的演示实验.利用激光辐照φ50μm的小孔产生的堵孔效应使X光的脉宽缩短，起到类似于短脉冲点背光源的作用.另外利用成像方法，实验演示了由面背光方式获得点背光技术，称之为点针孔背光技术.实验结果表明：结合堵孔效应和点背光方式，能获得与点背光同样的结果，这样可以避开点背光对激光器较为苛刻的要求.     

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.