金属光栅提高蓝光LED提取效率的研究

为了提高发光二极管(LED)的光提取效率，并比较不同光栅形状对LED光提取效率的影响，采用严格耦合波法优化了与矩形、等腰三角形、等腰梯形光栅分别集成的倒装LED，使它们出光面透射率达到最优，随后使用有限时域差分法模拟计算它们的光提取效率。经过模拟计算和理论分析可得3种不同结构LED最优光栅参量(光栅占空比f、光栅周期p、光栅厚度h)和过渡层厚度d分别是:f=0.35, p=150nm, h=80nm, d=190nm; f=0.45, p=175nm, h=80nm, d=190nm; f=0.7, p=150nm, h=80nm, d=190nm。结果表明，3种最优的LED结构在波长0.4μm~0.5μm范围内，矩形光栅倒装LED和等腰三角形光栅倒装LED出光面透射率相同，等腰梯形光栅倒装LED出光面透射率最低; 由于光透射率最低，导致等腰梯形光栅倒装LED光提取效率较低，最高仅为58.07%，但是由于等腰三角形光栅倒装LED特殊的光栅形状加上高的光透射率，其光提取效率可以达到77.75%。此研究可以为制备高光提取效率LED提供理论方法指导。     

高提取效率表面织构红光发光二极管

给出了用蒙特卡罗射线追踪法模拟发光二极管(LED)光提取效率的过程,并对表面织构LED的光提取效率进行了模拟分析,得到存在一组优化的表面织构参数,可使LED的光提取效率提高36%。通过湿法腐蚀和干法刻蚀相结合工艺,制备了表面织构的红光LED,器件的轴向光强提高了20.6%。理论和实验结果,表明表面织构技术是提高LED光提取效率的一个主要途径。     

一种具有亚波长光栅结构的光探测器的设计

高速智能光纤通信系统和网络的飞速发展对光电探测器提出了更高要求.利用严格耦合波(RCWA)理论,给出了在亚波长光栅(SWG)下方具有分布布拉格反射镜(DBR)结构的理论分析模型,将这种结构作为反射镜应用于谐振腔增强型光探测器(RCE PD)的设计中.仿真表明由于SWG的引入,只需要4对λ/4厚度的InGaAsP/InP系DBR,可使整体膜系结构实现在中心波长1.55 μm处反射率达到99.7%,在1.40 μm至1.62/μm范围内反射率高于99%.引入SWG后的RCE PD在1.55 μm附近的量子效率接近90%,串扰衰减系数与量子效率的乘积超过15 dB.有效地解决了InGaAsP/InP介质膜系DBR作为谐振腔反射镜反射率低、反射带宽窄的问题.     

凸球面矩型槽光栅的衍射特性

本文在用耦合波理论研究平面光栅的基础上,提出了分析和解决凸球面光栅衍射效率问题的方法,并从中得出一些有意义的结论：在凸球面光栅的口径半径比较小时,求解其衍射效率可以转化为平面光栅问题来处理。     

严格耦合波方法计算立体正弦光栅衍射效率

为了研究振幅型光栅的衍射效率,运用严格耦合波方法建立立体正弦透射光栅的计算模型。用Matlab软件编程计算衍射效率,并模拟了光栅层附近区域内的光场振幅和相位分布。计算结果表明模型衍射效率与平面的正弦型光栅有差别,其与周期,光栅厚度相关;在一定条件下两者非常接近。     

取样光栅的设计及衍射行为研究

设计了用于惯性约束核聚变系统的取样光栅。利用光全息学的基本原理,设计了记录全息取样光栅掩模的消像差光学系统,并使用光学设计软件ZEMAX分析了它的像差;还利用严格耦合波理论对取样光栅的衍射效率问题进行了深入的研究。研究发现,在占宽比和槽深这两个光栅结构参量中,槽深的变化对衍射效率更敏感。这些都为取样光栅的实际制作提供了有意义的结果。     

隧道再生双有源区AlGaInP发光二极管提取效率的计算

建立了发光二极管提取效率的理论计算模型,分析了影响隧道再生双有源区AlGaInP发光二极管提取效率的主要因素,包括从出光表面出射的光、体内的光吸收损耗、衬底对光的吸收损耗、金属电极对光的吸收损耗,模拟计算了隧道再生双有源区AlGaInP发光二极管的提取效率,计算得到隧道再生双有源区AlGaInP LED管芯的上有源区和下有源区提取效率分别为5．24％和9．16％。     

基于耦合波理论的体全息光栅衍射效率计算

基于耦合波理论,对反射体全息光栅的衍射效率进行了计算。给出了体全息图的边界条件,同时对基于耦合波理论的体全息光栅衍射效率的计算结果进行了分析。以便能为制作具有高衍射效率,低噪声的全息光栅做好准备。     

制作光纤光栅用相位掩模的衍射行为研究

利用严格耦合波理论对用于光纤光栅制作的相位掩模的衍射特性进行了深入的研究.研究发现,在紫外写入波长(248 nm)下,为了使零级衍射效率＜5%,且±1级的衍射效率＞35%,相位掩模的刻槽深度必须控制在230～280 nm,占宽比必须控制在0.48～0.65.同时,与标量衍射理论的结果进行了分析对比.这些都为相位掩模的实际制作提供了有意义的结果.     

严格耦合波法计算体布喇格光栅衍射效率

为了获得更精确的光栅衍射效率,采用严格耦合波理论建立体布喇格光栅衍射机理模型,分析了运用严格耦合波理论实现体光栅的衍射效率计算,并利用正交Legendre多项式展开法求解耦合波方程,取得了体布喇格光栅衍射效率稳定的数值解,得到的仿真结果符合理论计算。结果表明,相对于矩阵法,该算法具有更好的收敛速率,且比Ko-gelnik耦合波理论解法更精确。     

Enhancement of light extraction efficiency of GaN-based light-emitting diode using ZnO sol-gel direct imprinting

ZnO nano-structures were formed on transparent conducting oxide layer of GaN LED device on non-patterned (non-PSS) and patterned sapphire substrates (PSS). Since ZnO nano-structures were formed by sol-gel direct imprinting process, plasma etching process, which may create the plasma induced damage, was not used. Due to the ZnO nano-structures, light extracted from active layer was coupled with ZnO nano-structures and thus total internal reflection at the ITO layer was suppressed. According to electroluminescence measurement, the emission intensities of GaN LED devices with ZnO nano-structures, on both non-PSS and PSS sapphire substrates were increased by 20.5% and 19.0%, respectively, compared to GaN LED devices without ZnO nano-structures, due to the suppression of total internal reflection. Moreover, it is confirmed that there is no decrease of light extraction on side direction due to light focusing to vertical axis by nanostructure. Electrical performance of GaN LED devices were not degraded by ZnO sol-gel direct imprinting process.     

Improved light extraction efficiency and leakage characteristics in light-emitting diodes by nanorod arrays formed on hexagonal pits

We report the enhancement of light extraction efficiency (LEE) and electrical performance in GaN-based green light-emitting diodes (LEDs) using ZnO nanorods formed on the etched surface of p-GaN. Green LEDs with hybrid ZnO nanorod structures grown on the hexagonally etched topmost layer of the LEDs, show an improvement in electroluminescence intensity that is 3.5 times higher than LEDs without any other surface treatments. The improvement in LEE in LEDs with nanohybrid structures was confirmed by finite-difference time-domain simulation analysis. Besides LEE enhancement, the surface etching effects on the reduction of leakage current of fabricated LEDs were also investigated.     

采样光栅设计与衍射行为分析

从一维矩形光栅的衍射特性分析开始,将一维矩形光栅结构作一定的改变设计出采样光栅。将设计出的变周期采样光栅作适当的近似处理,然后用严格的耦合波分析方法对它的衍射特性进行了详细分析。     

High efficiency green phosphorescent top-emitting organic light-emitting diode with ultrathin non-doped emissive layer

Ultrathin non-doped emissive layer (EML) has been employed in green phosphorescent top-emitting organic light-emitting diodes (TOLEDs) to take full advantages of the cavity standing wave condition in a microcavity structure. Much higher out-coupling efficiency has been observed compared to conventional doped EML with relatively wide emission zone. A further investigation on dual ultrathin non-doped EMLs separated by a special bi-layer structure demonstrates better charge carrier balance and improved efficiency. The resulting device exhibits a high efficiency of 125.0 cd/A at a luminance of 1000 cd/m² and maintains to 110.9 cd/A at 10,000 cd/m².     

简易发光二极管测试仪的设计研究

为方便快捷的测试出发光二极管的各项特性参数,详细介绍了一种简易、低成本的发光二极管测试仪的系统构成、功能和硬件设计,并用该测试仪测试了几种不同颜色发光二极管的伏安、光照、颜色和方向特性参数.测试结果表明该测试仪可以方便、快速和准确地测量出发光二极管多项特性参数,并具有低成本、易操作等优点.     

基于倒扣技术的190~225 GHz肖特基二极管高效率二倍频器

基于分立式GaAs肖特基势垒二极管,研制出了190～225 GHz高效率二倍频器.50 μm厚石英电路利用倒扣技术,实现二极管的良好散热、可靠的射频信号及直流地.通过数值分析方法,二极管非线性结采用集总端口模拟,提取二极管的嵌入阻抗,以设计阻抗匹配电路.在202 GHz,测得最高倍频效率为9.6％,当输入驱动功率为85.5 mW时,其输出功率为8.25 mW;在190～225 GHz,测得倍频效率典型值为7.5％;该二倍频器工作频带宽、效率响应曲线平坦,性能达到了国外文献报道的水平.     

ITO掩膜干法粗化GaP提高红光LED的提取效率

采用氧化铟锡(ITO)颗粒掩膜,经感应耦合等离子体(ICP)刻蚀后制作了表面粗化的红光发光二极管(LED),并且研究了ITO腐蚀时间对粗化表面形貌的影响。测试结果表明,当粗化颗粒的大小为200～500 nm、腐蚀深度约200～400 nm时,能使制作的表面粗化红光LED在20 mA注入电流下光提取效率提高30%以上。并且,表面粗化不会影响LED的发光强度角度分布。     

Design of white tandem organic light-emitting diodes for full-color microdisplay with high current efficiency and high color gamut

Microdisplays based on organic light-emitting diodes (OLEDs) have a small form factor, and this can be a great advantage when applied to augmented reality and virtual reality devices. In addition, a high-resolution microdisplay of 3000 ppi or more can be achieved when applying a white OLED structure and a color filter. However, low luminance is the weakness of an OLED-based microdisplay as compared with other microdisplay technologies. By applying a tandem structure consisting of two separate emission layers, the efficiency of the OLED device is increased, and higher luminance can be achieved. The efficiency and white spectrum of the OLED device are affected by the position of the emitting layer in the tandem structure and calculated via optical simulation. Each white OLED device with optimized efficiency is fabricated according to the position of the emitting layer, and red, green, and blue spectrum and efficiency are confirmed after passing through color filters. The optimized white OLED device with color filters reaches 97.8% of the National Television Standards Committee standard.     

宽波长太阳能电池抗反射层结构设计

为了降低太阳能电池表面对入射光的反射,提高其光电转换效率,设计了入射光谱在400～1100 nm宽波长范围内的二维亚微米抗反射层结构.该结构主要由高折射率ZnS膜层、低折射率MgF_2膜层及二维亚微米光栅层等组成.采用严格耦合波分析理论计算了此结构的反射特性,当ZnS膜层、MgF_(2)膜层、光栅深度及光栅周期分别为50 nm、150 nm、200 nm及400 nm,入射角在0～80°变化时,其平均反射率为7.76%.计算结果表明:所设计的抗反射层结构可有效降低太阳能电池表面对入射光的反射,从而提高其光电转换效率.     

Low driving voltage white organic light-emitting diodes with high efficiency and low efficiency roll-off

Single emission layer white organic light-emitting diodes (WOLEDs) showing high color stability, low turn-on voltage, high efficiency and low efficiency roll-off by incorporating iridium(III) bis[(4,6-difluo-rophenyl)-pyridinato-N,C2] (FIrpic) and bis(2-phenylbenzothiazolato) (acetylacetonate)iridium(III) (Ir(BT)₂(acac)) phosphors dyes have been demonstrated. Our WOLEDs without any out-coupling schemes as well as n-doping strategies show low operating voltages, low turn-on voltage (defined for voltage to obtain a luminance of 1 cd/m²) of 2.35 V, 79.2 cd/m² at 2.6 V, 940.5 cd/m² at 3.0 V and 10 300 cd/m² at 4.0 V, respectively, and achieve a current efficiency of 40.5 cd/A, a power efficiency of 42.6 lm/W at a practical brightness of 1000 cd/m², and a low efficiency roll-off 14.7% calculated from the maximum efficiency value to that of 5000 cd/m². Such improved properties are attributed to phosphors assisted carriers transport for achieving charge carrier balance in the single light-emitting layer (EML). Meanwhile the host–guest energy transfer and direct exciton formation process are two parallel pathways serve to channel the overall excitons to dopants, greatly reduced the unfavorable energy losses.