AlGaN-Based Deep-Ultraviolet Light Emitting Diodes Fabricated on AlN/sapphire Template

We report on the growth and fabrication of deep ultraviolet （DUV） light emitting diodes （LEDs） on an AIN template which was grown on a pulsed atomic-layer epitaxial buffer layer. Threading dislocation densities in the AlN layer are greatly decreased with the introduction of this buffer layer. The crystalline quality of the AlGaN epilayer is further improved by using a low-temperature GaN interlayer between AlGaN and AlN. Electroluminescences of different DUV-LED devices at a wavelength of between 262 and 317nm are demonstrated. To improve the hole concentration of p-type AlGaN, Mg-doping with trimethylindium assistance approach is performed. It is found that the serial resistance of DUV-LED decreases and the performance of DUV-LED such as EL properties is improved.     

Reduction of Electron Leakage of AlGaN-Based Deep Ultraviolet Laser Diodes Using an Inverse-Trapezoidal Electron Blocking Layer

To improve the optical and electrical properties of AlGaN-based deep ultraviolet lasers,an inverse-trapezoidal electron blocking layer is designed.Lasers with three different structural electron blocking layers of rectangular,trapezoidal and inverse-trapezoidal structures are established.The energy band,electron concentration,electron current density,P-I and V-I characteristics,and the photoelectric conversion efficiency of different structural devices are investigated by simulation.The results ...     

Optimization of AlGaN-Based Deep Ultraviolet Laser Diodes with Graded Rectangular Superlattice Electron Blocking Layer and Graded Trapezoidal Superlattice Hole Blocking Layer

Journal of Russian Laser Research - To improve the carrier confinement capability and optimize the performance of deep ultraviolet laser diodes (DUV-LDs), we propose the graded rectangular...     

High Power 940 nm Al-free Active Region Laser Diodes and Bars with a Broad Waveguide

The 940 nm Al-free active region laser diodes and bars with a broad waveguide were designed and fabricated. The stuctures were grown by metal organic chemical vapour deposition. The devices show excellent performances. The maximum output power of 6.7 W in the 100 μm broad-area laser diodes has been measured, and is 2.5 times higher than that in the Al-containing active region laser diodes with a narrow waveguide and 1.7 times higher than that in Al-free active region laser diodes with a narrow waveguide. The 19% fill-factor laser diode bars emit 33 W, and they can operate at 15W with low degradation rates.     

High Power 940 nm Al-free Active Region Laser Diodes and Bars with a Broad Waveguide

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Organic Light Emitting Diodes Using Doped Alq3 as the Hole-transport Layer

Effects of 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane （F4TCNQ） doping on the hole conductivity of Alq3 layer are measured. In the hole-only device of Alq3, the current densities increase in 1-3 orders of magnitude upon doping with F4TCNQ, suggesting that the doping can effectively enhance the hole-injection and hole- transport ability of Alq3. An organic light-emitting device using an F4TCNQ doped Alq3 layer as the hole- injection and hole-transport layer, and pristine Alq3 as the electron-transport and emitting layer is fabricated and characterized. Bright emission is achieved in the simple OLED with p-doped Alq3 as the hole-transport layer and the intrinsic Alq3 as the electron-transport and emitting layer. The emitting efficiency and brightness of the device are further improved by inserting a thin electron block layer to confine the carrier recombination zone in the middle of the organic layers.     

掺杂不同一维纳米材料的空穴缓冲层对有机电致发光器件性能的影响

对一维纳米材料在空穴缓冲层PEDOT中的作用进行了研究。光致发光表明在PEDOT中掺杂一维纳米材料(二氧化钛纳米管和氧化锌纳米棒)可以提高双层样品PEDOT/MEH-PPV的发光效率。拉曼光谱的结果说明正是由于一维纳米材料与PEDOT之间存在的强相互作用,才减少了PEDOT/MEH-PPV界面上猝灭发光的缺陷态的产生。在以MEH-PPV作为发光层的聚合物电致发光器件中,在PEDOT中掺杂二氧化钛纳米管和氧化锌纳米棒后,器件的最大效率分别提高了2倍和2.5倍。     

Low-Threshold-Current and High-out-Power 660 nm Laser Diodes with a p-GaAs Current Blocking Layer for DVD-RAM/R

We investigate a new structure of high-power 660-nm AlGaInP laser diodes. In the structure, a p-GaAs layer is grown on the ridge waveguide serving as the current-blocking layer, and nonabsorbing windows are only fabricated near the cavity facets to increase the catastrophic-optical-damage level. Stable fundamental mode operation was achieved at up to 80roW without kinks, and the maximum output power was 184roW at 22~C. The threshold current was 40 mA.     

A Traveling-Wave Model of Laser Diodes with Consideration for Thermal Effects

We investigate the static and dynamic thermal effects using the large-signal traveling-wave model of laser diodes. To cope with the substantial difference in the time constants of the thermal and the optical processes, a simple and efficient iteration method is proposed and demonstrated. Therefore instead of following the time sequence constrained by the finite difference time interval, by the iteration method, we can easily locate the equilibrium point of both the thermal and optical states. Both static and transient states of a laser diode with consideration of the thermal effects are simulated. The various thermal time constants of directly modulated distributed feedback lasers observed recently are explained based on the thermal traveling-wave model.     

Analysis of the Characteristics of Laser and Superluminescent Diodes

It is shown that superluminescent diodes rank below laser diodes in energy characteristics, but they have a wider emission spectrum and lower noise level. The amplitude-frequency and noise characteristics of the laser diode correlate with each other, whereas there is no such correlation for the superluminescent diode. The photon density distribution along the active area is more homogeneous for the laser diode than for the superluminescent one. Presented at the 5th International Scientific-Technical Conference “Quantum Electronics,” November 22–25, 2004, Minsk, Belarus. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 5, pp. 689–693. September–October, 2005.     

驱动电压和主体材料对染料掺杂有机电致发光器件的影响

采用对比使用掺杂系统的有机电致发光器件(OLEDs)在不同偏置电压下电致发光(EL)光谱的方法,观察了主体材料8-hydroxyquinoline aluminum(Alq3)中掺杂红色荧光染料4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4Hpyran(DCJTB)发射光谱的变化,研究了偏置电压对掺杂系统中载流子复合区域的影响。另外,通过对比采用不同主体材料的掺杂系统的电致发光(EL)和光致发光(PL)光谱,讨论了主体材料Alq3和N,N′-diphenyl-N,N′-bis(1-naphthyl)(1,1′-biphenyl)-4,4′-diamine(NPB)不同的掺杂效果。结果表明,随着偏置电压的增大,使用掺杂系统的器件中载流子复合区域逐渐向空穴传输层(HTL)移动,作为主体材料应具有高的能量传递效率,且应对染料具有低的浓度猝灭效应。     

LD光束在自聚焦透镜中的传输特性

基于分析激光二极管光束传输特性，运用厄米-高斯光束描述其远场分布．将自聚焦透镜用于激光二极管的光束整形，用2阶传输矩阵描述自聚焦透镜．运用Collins衍射积分公式，分析了LD光束在自聚焦透镜中传输场分布的解析表达式．在此基础上，数值计算了一种LD光束在自聚焦透镜中场分布．该模型结构简单，可用于分析光束传输特性和设计光束整形系统．     

Mode Structure and the Envelope of a High-Power Pulse in a Nonsymmetric Graded-Index Waveguide Layer

Radiophysics and Quantum Electronics - We consider a weakly nonlinear process of propagation of a modulated pulse with high-frequency filling in a plane graded-index waveguide layer. The transverse...     

发光层位置对白光有机发光二极管的影响

同一种主体材料MADN中混掺不同的掺杂剂,分别制备了两种白光有机发光二极管,测试并研究了它们的发光效率、寿命、发光亮度、电致发光光谱以及色平衡度。结果表明,两种白光器件的性能受发光层的顺序和厚度的影响显著。发光层顺序由阳极到阴极方向为橙/蓝的器件的稳定性要优于发光层顺序为蓝/橙的器件,这是由于橙光发光层中的rubrene对空穴的陷进作用可捕获穿越橙光发光层中的空穴,从而有效地调控了器件内部的电子、空穴浓度的平衡。通过对器件的优化,制得了色坐标为(0.3201,0.3459)的接近标准白光的有机电致发光器件。     

Fluorescence Enhancement of a Polymer Planar Waveguide Doped with Rhodamine B and Ag Nanoparticles

Planar polymer multi-model waveguides doped with Ag nano-particles and rhodamine B are fabricated and investigated by the spectroscopy analysis method as well as the M-line method. Experimental results shown that fluorescence enhancement occurs when excited by a wide band wavelength with Ag nano-particle concentration at a certain level. The maximum enhancement factor in our experiment is obtained to be about 3.8 when excited by 350 nm. Our study may have potential applications in polymers optical elements, such as polymer waveguide lasers and amplifiers.     

Observation of Optical Bistability and Multi-Stability in the Dielecrtric Slab Doped with a Quantum well Waveguide

The optical bistability (OB) and multi-stability (OM) behavior in a dielectric slab medium doped with semiconductor quantum well nanostructure has been discussed by employing the spin coherence effect. It is shown that, by changing the relative phase of applied fields the bistable behavior switches from OB to OM or vice versa in a dielectric medium. The effect of the frequency detuning of laser fields on the OB and OM behavior are also discussed in this paper.     

Natural Electromagnetic Waves in a Circular Waveguide with a Chiral and a Dielectric Layer

Based on particular solutions of a system of wave equations which describe electromagnetic processes in an unbounded biisotropic medium and are represented in the form of generalized power series, a dispersion equation is obtained for a two-layer circular waveguide with a chiral and a dielectric layer. The solution of the dispersion equation is analyzed for some types of natural waves.     

Self-Consistent Model and Numerical Analysis of VCSEL''s Laser Diodes

A self-consistent model of vertical-cavity surface-emitting lasers (VCSEL's) is presented in this paper, in which the carrier diffusion rate equation, the photon density rate equation, and the thermal conduction equation are considered simultaneously. The nonuniform heat flux density distribution in the active region due to the current-spreading effect is taken into account. The effects of temperature on gain and transparency carrier density are also included in this model. It is nonlinearly and self-consistently solved in the Matlab environment. The transient and lateral distribution characteristics of the carrier and photon densities and the junction temperature are investigated. Some interesting results are gotten and analyzed.     

High Coupling Efficiency of the Fiber-Coupled Module Based on Photonic-Band-Crystal Laser Diodes

The coupling efficiency of the beam combination and the fiber-coupled module is limited due to the large vertical divergent angle of conventional semiconductor laser diodes. We present a high coupling efficiency module using photonic-band-crystal(PBC) laser diodes with narrow vertical divergent angles. Three PBC single-emitter laser diodes are combined into a fiber with core diameter of 105μm and numerical aperture of 0.22. A high coupling efficiency of 94.4% is achieved and the brightness is calculated to be 1.7 MW/(cm~2.sr) with the injection current of 8 A.