Efficient Organic Multi—quantum Well Electroluminescent Devices Using Aluminum as Cathodes

Organic green light emitting devices(LEDs)with multi-quantum well(MQW)structure were fabricated.Aromatic diamine(TPD)was used as holetransporting layer and potential barrier layer;Tris(8-hydroxyquinoline)aluminunum(Alq3)was acted as electron-transporting emitter and MQW green emitter.Airstable aluinum(Al)was used as electron-injection contact.The influence of the thickness of potential barrier layer and the number of quantum well on the electroluminescent(EL)efficiencies of the devices was investigated.The organic LEDs with two quantum wells showed enhanced EL efficiencies.Maximum external quantum efficiency and brightness were 1.04% and 7000cd/m^2,respectively.     

Spectral Properties of Yellow Fluorescent Powder for White LEDs

Much attention has been paid to white LEDs because of their potential applications in the illumination.The doping of rate earth ions plays an important role in the optical properties of yellow fluorescent powder.And mainly aiming to raise the intensity and the luminous rate of the white LEDs and by photoluminescence and electroluminescence,the luminescence spectrum of yellow fluorescent powder bought from different places is measured.Furthermore,the luminous intensity in the normal direction and the angle distribution of half maximum power for the white LEDs packed with cylindrical φ5 epoxy on the same blue GaN chips are also measured under the same manufacture conditions.The results show that the yellow fluorescent powder bought from China mainland has higher optical output rate than that bought from China Taiwan and hence is more suitable to fabricate the white LEDs for practical use.     

Wide reflected angle DBR red light LED

The coupled DBR LED with one DBR for reflecting normal incidence light and the other for reflecting inclined incidence light has been grown by MOCVD. For improving the conventional DBR which was used to increase light extraction efficiency in AlGaInP red light LED is analyzed. At 20 mA Dc injection current, the LED peak wave length is 630 nm, and the light intensity of on axis is 137 mcd. The output light power is 2.32 mW. The light intensity and output light power have been improved compared with the conventional LEDs.     

Enhancing extraction efficiency from GaN-based LED by using an omni-directional reflector and photonic crystal

To enhance the light extraction efficiency of traditional light-emitting diodes（LEDs） by reducing the total internal reflection,an omni-directional reflector（ODR） and photonic crystal are adopted in the paper.The structures of photonic crystal and the ODR are designed by diffraction theory and finite difference time domain（FDTD） method.The photonic crystal is employed in the p-GaN layer and the ODR composed of TiO2/SiO2 is designed between the active region and substrate.The simulation results indicate that the light extraction of LEDs can be enhanced by 11.6 times,and the external quantum efficiency of LEDs will be effectively improved.     

使用ZnO电流扩展层提高GaN基LED提取效率

Gallium nitride （GaN） based light emitting diodes （LEDs） with a thick and high quality ZnO film as a current spreading layer grown by metal-source vapor phase epitaxy （MVPE） are fabricated successfully. Compared with GaN-based LEDs employing a Ni/Au or an indium tin oxide transparent current spreading layer, these LEDs show an enhancement of the external quantum efficiency of 93% and 35% at a forward current of 20 mA, respectively. The full width at half maximum of the ZnO （002） ω-scan rocking curve is 93 arcsec, which corresponds to a high crystal quality of the ZnO film. Optical microscopy and atomic force microscopy are used to observe the surface morphology of the ZnO film, and many regular hexagonal features are found. A spectrophotometer is used to study the different absorption properties between the ZnO film and the indium tin oxide film of the GaN LED. The mechanisms of the extraction quantum efficiency increase and the series resistance change of the GaN-based LEDs with ZnO transparent current spreading layers are analyzed.     

GaN-based LED基础光栅结构实现光的表面等离极化增强

The transmitting light in GaN-based LED with 30 nm thickness metal film grating is investigated. We proposed a basic grating structure model to enhance light intensity in GaN material, which was simpler and cheaper. We calculated and analyzed the structure with different parameters, and studied the numerical simulation results of Ag-films/Al-films/Au-films. With a simple A1 or Ag basic grating structure, the 7.4-7.6 times intensity of 550 nm light can be obtained easily, and the enhancement efficiency is better than others.     

InGaN multiple quantum well based light-emitting diodes with indium composition gradient InGaN quantum barriers

To improve the internal quantum efficiency(IQE) and light output power of In Ga N light-emitting diodes(LEDs), we proposed an In-composition gradient increase and decrease In Ga N quantum barrier structure. Through analysis of its P-I graph, carrier concentration, and energy band diagram, the results showed that when the current was 100 m A, the In-composition gradient decrease quantum barrier(QB) structure could effectively suppress electron leakage while improving hole injection efficiency, re...     

Application of metal halide perovskite photodetectors

In recent years,metal halide perovskite materials have attracted wide attention in the fields of photovoltaics(PVs),light-emitting diodes(LEDs)and photodetectors(PDs)due to their excellent light absorption[1-6],adjustable bandgaps and long carrier diffusion length.Compared with commercial Si and GaN photodetectors,perovskite photodetectors(PPDs)present wider light detection range,higher sensitivity and higher external quantum efficiency(EQE)[7-9].     

Detection and Ranging System of Flight Aid Lights

Dynamic detection based on optics sensors and ranging radars is a new method to detect the luminous intensity of flight aid lights. The optics sensors can get the illumination information of each light, the ranging radar gets the distance information, and then data amalgamation technology is used to compute the luminous intensity of each light. A method to modify the errors of this dynamic detection system is presented. It avoids the accumulation error and measurement carrier＇s excursion error by using peak value detection based on optics sensors to estimate the accurate position of each light, then to modify the lights＇ lengthways distance information and transverse position information. The performance of the detection and ranging system is validated by some experiments and shown in pictures.     

Correlated Color Temperature Tunable Multi-chip Light Emitting Diodes Light Source Design

One of the methods to derive white light from light emitting diodes（LEDs） is the multi-chip white LED technology, which mixes the light from red, green and blue LEDs. Introduced is an optimal algorithm for the spectrum design of the multi-chip white LEDs in this paper. It optimizes the selection of single color LEDs and drive current controlling, so that the multi-chip white LED achieves the target correlated color temperature （CCT）, as well as high luminous efficacy and good color rendering. A CCT tunable LED light source with four high-power LEDs is realized based on the above optimal design. Test results show that it maintains satisfactory color rendering and stable luminous efficacy across the whole CCT tuning range. Finally, discussed are the design improvement and the prospect of the future applications of the CCT tunable LED light source.     

硅薄膜矩形空芯波导太阳能电池光捕获性能的研究

为提高薄膜电池对光的捕获能力, 将平面硅薄膜电池制 作成矩形空芯波导结构,对其太阳光注入方式、光捕获能力和光-电转换效能进行了理论和 实验探讨。基于 多层膜反射理论和波导反射模型对波导电池光捕获效果的预测表明,波导电池能够将入射光 限制在空芯结 构内多次反射和吸收,具有较平面电池更高的光捕获能力。测定了不同平行光束在不同入射角度 下平面和波导 电池的光捕获功率和光-电转换效能的结果表明,波导电池对入射光功率近似全部捕获,其 光-电功率转换效能 较对应的平面电池有3～5倍的提升。对不同截面尺寸和长度的单结空芯波导电池光捕获率 进行了计算,提 出从电池膜层结构和空芯几何尺寸参数优化硅薄膜矩形空芯波导电池的思路,通过优化有 望实现用小于多结平面电池外形尺寸的单结空芯波导电池达到更好的光捕获效果。     

基于几何相位超表面的Ince-Gaussian矢量涡旋光场聚焦

为了实现电介质超表面的聚焦功能和对光场相位的调控,采用几何相位调制原理设计微元结构及空间分布,以SiO₂为基底、亚波长TiO₂椭圆柱的六边形晶胞为基本结构,设计了一种相位突变呈抛物线梯度分布的聚焦超表面,适用于480nm～580nm波段。基于此结构进行了理论分析和实验验证,发现该结构对线偏振光聚焦,其归一化后的半峰全宽约为428nm,而对矢量光聚焦约为258nm,获得了更出色的聚焦效果。研究了3阶和4阶Ince-Gaussian矢量光场通过该超表面后的聚焦特性,得到了聚焦场能保持入射矢量光场的基本空间结构,但中心结构信息会有损失的结果,即Ince-Gaussian矢量涡旋光场由于涡旋相位的存在,聚焦后会呈现破缺的空间结构。结果表明,超表面结构和入射光场矢量结构之间的匹配程度是影响聚焦特性的重要因素。该研究为理解复杂矢量光场的超表面聚焦机理提供了参考。     

一种纹理与结构光叠加的立体视觉改进算法

为降低复杂纹理与结构光叠加对立体匹配算法视差结果的影响,提出一种针对纹理与空间编码结构光叠加情况下的立体视觉改进算法。通过4种空间编码结构光与三种立体匹配算法(BM、SGBM、NCC)对单一平面与电木压模工件进行视差重建,发现叠加会导致双目立体视觉无法计算出真实视差。本文通过对比引入结构光前后两次拍照视差,在纹理复杂区域内用加入结构光之前视差替换加入结构光后坏点视差,实现对纹理与结构光叠加处视差优选,从而提高视差重建完整性。实验对比发现,在四种不同性能结构光下改进前后的三维重建结果可以验证算法有效性,算法提升了平面区域深度检测精度的1%,优化了工件视差重建,达到了提高三维重建完整性的目的。     

平板波导光谱仪中光栅多次衍射杂散光的抑制

平板波导光谱仪是一种紧凑型光谱仪,其光栅多次衍射杂散光大,需要进行抑制。首先研究了多次衍射杂散光的形成过程,并通过TracePro软件详细分析了多次衍射杂散光的传播路径和大小。然后根据杂散光的空间特性和波长特性对其进行分类,采取不同的抑制方法。在不改变原有光学结构的基础上提出了利用滤光片和挡光板来抑制多次衍射杂散光的方法,滤光片的参数和位置需要精心选择以达到最好的抑制效果。最后对增加抑制结构前后的杂光系数进行对比分析。结果表明,多次衍射杂散光得到了很好的抑制,最大杂光系数从5.3%降到0.033%,平均杂光系数从1.9%降到0.0018%。     

大功率激光光学系统杂散光分析的数据结构

文中主要研究发功率激光光学系统光学表面多次反射而形成的杂散光及其数学模型与计算方法，提出了杂散光分析的二叉树数据结构。利用这种数据结构，作者编制了激光光学系统杂散光分析软件，针对两个实例建立了近轴鬼光束树。实例计算表明，采用该数据结构可以全面描述杂散光状况，并根据设计人员的要求捕捉危害较大的鬼像。     

正装、倒装结构GaN 基LED提取效率分析

从几何和物理光学角度分析了影响GaN基LED提取效率的因素,并以理论分析为基础,利用Monte-Carlo光线追踪的方法,对GaN基LED的提取效率进行模拟,比较不同器件结构对LED提取效率的影响.模拟结果表明,采用倒装结构可以显著提高GaN基LED的提取效率,Ni/Au透明电极透射率为0.6～0.9时,相对于普通正装结构,倒装结构可以使LED提取效率提高39%～16%.     

LD泵浦光在侧泵模块水冷结构传输中的偏振态变化和光强衰减分析

以LD泵浦光在侧泵模块水冷结构中的传输过程为研究内容,基于模块结构参数、光波传输特性及介质透光特性,系统分析了泵浦光在各介质表面和内部的偏振态变化、光强衰减过程及变化规律。重点分析了由介质表面菲涅尔效应和内部吸收效应等造成的光强衰减;计算了泵浦光在水冷结构中单次往返过程的损耗系数和偏振态变化矩阵。分析结果对于优化模块泵浦效率、增强散热效果等有一定借鉴作用。     

微型投影系统光路设计

为了改善传统的数字光处理投影系统（DLP）体积较大、结构复杂、成本较高、对光源的利用效率较低的问题,采用一种基于单颗三色发光二极管作为照明光源,单颗透镜形成平行光的新型DLP投影光路结构的方法,对传统光路进行了改进与优化。无需传统光路中的色轮,透镜直接实现了传统投影光路中聚光和匀光的复杂结构,并利用TRACEPRO软件进行建模,通过光线追迹对该投影光路进行了光学分析。结果表明,整个光学系统的体积控制在76.8mm×32.2mm×25mm,光能利用率达到了60.1%,光斑均匀性达到了96.6%,屏幕表面的光通量为21.7lm。该研究减小了投影光路体积,简化了光学结构,提高了光能利用率。     

大尺寸超薄背光模组研究及产品可行性分析

超薄液晶电视越来越普及,文章从大尺寸背光模组结构上推理出侧光式结构实现超薄的优势,然后从侧光式结构和材料上分析了实现超薄的各种可能性。     

双面金属包覆单轴晶体波导的偏振转换研究

利用转移矩阵方法计算了双面金属包覆单轴晶体波导结构中的色散曲线、反射谱。结果表明,双面金属包覆结构使得波导可以被自由空间光场激发;单轴晶体的光轴取向能对该结构中的波导模式进行调控,使入射光波中的Ey、Ez分量发生相互转换耦合,从而在波导层中形成杂化模。通过调节耦合金属层厚度可以对出射光偏振状态的控制,实现TE线偏振入射光向TM线偏振反射光的转换以及线偏振入射光向圆偏振反射光的转换。