有机电致发光的效率

描述了评价有机电致发光性能的重要指标－－发光效率问题,从发光机制考虑,一般常用外量子效率和内量子效率来评价。外量子效率是有机电致发光器件输出光子数与注入电子数之比;内量子效率是产生在器件内部的光子数与液入电子数之比,对于光子能否输出到器件外部无关紧要。评价器件性能还有一些其他效率评价方法,如能量效率,功率效率等,特别是外功率效率（1m/W),电流效率（cd/A)也常常用于表征有机电致发光性能,但它们与发光光谱的视觉灵敏度有关,对紫外外辐射器件不适用,另外,利用三重态激子发射可以提高EL器件效率,理论上可达100％,器件结构及材料对器件外量子效率影响至关重要。     

非旋波近似下有外加驱动场时二态量子系统的退相干性

采用非旋波近似,讨论了热库中二态量子系统在外加驱动场作用下的退相干性。利用系统的演化酉算符,计算出了二态量子系统的约化密度矩阵非对角矩阵元。结果表明：二态量子系统的量子相干性与其初始状态、热库和外加驱动场的频率、二态量子系统与热库和驱动场的耦合强度等因素有关。确定了外加驱动场与退相干性之间的关系,并得到了外加驱动场的时间演化满足特定条件时,可保持系统的相干性。     

红外PbX量子点光致发光特性研究

利用尺寸效应调节发光波长,Pb X量子点可用于近红外波段的光致发光。实际应用中对其辐射荧光特性的检测与评估,在设计器件、开发系统、提高量子点光致发光有效利用率等方面具有重要意义。本文对比分析了不同尺寸Pb X量子点在近红外波段的吸收、发射光谱,并对Pb X胶质量子点制成薄膜后的光致发光光谱进行了检测分析。光谱对比显示,量子点薄膜化后荧光辐射波长峰值会发生一定量的红移,全波半宽也会增大。提出一种在实际应用中检测量子点光致发光的空间分布情况并估算其效率的方法,同时利用该方法对两种Pb X量子点薄膜样品进行了检测分析。分析表明,量子点薄膜样品的光致发光功率与探测器相对样品发光表面的角度位置有关,可以反映出薄膜中量子点的分布;两种被测样品近红外激光照射下的荧光功率转换效率分别可达2.51%和2.06%,适于工程应用。     

玻璃中半导体CdSSe量子点的界面态发光

研究了玻璃中半导体CdSSe量子点的界面态发光.在10K温度下,通过PL和吸收光谱实验,研究了半导体CdSSe量子点,并进行了变温测量.分析了半导体量子点的量子尺寸效应、温度对PL和吸收光谱的影响.实验发现PL谱中在1.84eV和1.91eV有两个尖锐的发光峰,且峰位不随量子点尺寸大小变化而漂移,这是来源于与量子点尺寸无关的界面态的发光;同时,界面态的发光强度应与量子点半径成反比,实验结果与之相符.     

玻璃中半导体CdSSe量子点的界面态发光

研究了玻璃中半导体Cd SSe量子点的界面态发光.在10 K温度下,通过PL 和吸收光谱实验,研究了半导体Cd SSe量子点,并进行了变温测量.分析了半导体量子点的量子尺寸效应、温度对PL 和吸收光谱的影响.实验发现PL 谱中在1.84e V和1.91e V有两个尖锐的发光峰,且峰位不随量子点尺寸大小变化而漂移,这是来源于与量子点尺寸无关的界面态的发光;同时,界面态的发光强度应与量子点半径成反比,实验结果与之相符.     

碲镉汞红外探测器量子效率计算研究

首先分析了量子效率计算的相关方法,然后分析红外碲镉汞探测器测试过程。对器件进行电学性能测试及光谱响应测试基础上,利用测试方法和测试数据计算出探测器产生的电子数。再将实际电子数与理论分析的光子数相比,计算出探测器对不同红外波段量子效率,最高可达66 %,达到了国外同类型器件响应的量子效率指标。本文的研究为评价碲镉汞探测器的光电转换性能提供了一种有效的方法。     

PbSe量子点光纤激光器的数值模拟

提出了一种新型的光纤激光器--掺量子点的光纤激光器(QDFL).在QDFL中,利用PbSe量子点具有大发射截面的特点,将PbSe量子点作为激光器的激活介质,对QDFL进行了计算机数值模拟.数值计算了掺PbSe量子点光纤激光器的激光功率及饱和长度,并给出了不同输出镜反射率对激光功率的影响.结果表明:与传统的掺镱离子的光纤激光器相比,QDFL的输出激光功率更高,增益系数更大,光纤的饱和长度较短.QDFL的激光功率与光纤长度密切相关,饱和功率与掺杂浓度无关.改变谐振腔出射镜的反射率,可以改变激光功率.这些结果有待于实验的证实和检验.     

单电子器件中电子在耦合能级上的几率分布

两量子点耦合时,根据简并态微扰理论,单量子点的一个能级分裂为系统的两个能级,即对称态和反对称态,当单电子从外部隧穿进入一个量子点时,则电子在两耦合的量子点间振荡,本文讨论了电子在两能级上分布几率随时间的演化规律。     

能量选择性电子热机和制冷机的性能特征分析

 针对不同热电子库组成的电子热机和制冷机系统,本文运用费米—狄拉克统计分布计算了在球坐标下两不同热电子库的净电子流密度随能量的分布函数,进而得到相应的热流.接着,计算了电子热机和制冷机各性能参数,数值模拟出该机的优化性能特征曲线.从而得到提高电子机工作性能的方法.     

980nm InGaAs应变量子阱激光器及组合件

利用分子束外延技术研制出了高质量InGsAs/GaAs应变量子阱材料及量子阱激光器.脊形波导窄条形量子阱激光器的阈值电流和微分量子效率分别为15mA和0.8 W/A,线性输出功率大于150mW,基横模输出功率可达100mW.InGaAs应变量子阱激光器和单模光纤进行了耦合,其组合件出纤光功率典型值为40mW,最大值可达60mW.显示出了高的基横模输出功率和高的耦合效率.其组合件在40～60mW下,中心发射波长在977nm.满足了对掺铒光纤高效率泵浦的波长要求,成功地研制出适于掺铒光纤放大器用的应变量子阱激光器.     

量子点激光器瞬态响应及调制特性分析

基于二能级系统建立量子点激光器的载流子-光子速率方程模型,分析量子点激光器的瞬态响应和调制特性,获得其动态特性.同时分析了注入电流对量子点激光器输出光子密度的影响,随着注入电流的增大,激光器光电延迟时间缩短,弛豫过程缩短,弛豫振荡频率增大,且输出光子峰值和稳态功率增加,适当增加注入电流可拓宽量子点激光器调制带宽.通过小信号调制分析,发现量子点激光器上限调制频率比普通激光器高一个数量级,证明了其具有良好的高频调制特性.     

高性能InAs/GaAs量子点外腔激光器

为了获得高性能的量子点外腔激光器(ECL),利用InAs/GaAs量子点Fabry-Perot(FP)腔激光器研制了光栅外腔可调谐ECL。对InAs/GaAs量子点ECL进行了一系列的性能测试,主要包括单模稳定性测试、单模调谐范围测试、阈值电流密度测试、无跳模连续调谐测试和输出功率测试。在室温条件下获得了24.6nm的连续调谐范围,覆盖波长从999.2nm到1 023.8nm,并且实现了波长无跳模连续调谐。在调谐范围内最低阈值电流密度为1 525A/cm2,而且在中心波长处获得的单模输出功率为15mW,单模边模抑制比(SMSR)高达35dB。研究结果表明,通过构建光栅外腔可以实现高性能的InAs/GaAs量子点ECL。     

Temperature-dependent characteristics and single-mode performanceof AlGaInP-based 670-690-nm vertical-cavity surface-emitting lasers

We report on temperature dependent characteristics and single mode performance of one-wave cavity, planar implanted, AlGaInP-based vertical-cavity surface emitting lasers. By optimizing the overlap between the gain peak and the cavity mode of the structure, we demonstrate record device performance, including 8.2 mW maximum output power and 11% power conversion efficiency for multimode operation and 1.9 mW and 9.6% power conversion efficiency for single mode operation at 687 nm. Improved performance at elevated temperatures is also achieved, with 1.5 mW output power demonstrated at 50°C from a 15-μm-diameter device     

Self-Consistent Analysis of Carrier Confinement and Output Power in 1.3-$mu{hbox {m}}$ InAs–GaAs Quantum-Dot VCSELs

A self-consistent model comprising rate equations and thermal conduction equation is used to analyze the influence of self-heating on the carrier occupation, quantum efficiency, and output power of 1.3- $mu{hbox {m}}$ InAs–GaAs quantum dot (QD) vertical-cavity surface-emitting lasers (VCSELs). The simulation results show that the poor hole confinement in QDs is due to the thin wetting layer, and increase in QD density and layer number can significantly improve the self-heating effect and quantum efficiency of the device. The output power of the QD VCSEL is mainly determined by the quantum efficiency. High output power can be achieved by the high number of QD layers and QD density. However, there exists an optimized number of QD layers ($sim$15) to achieve the highest output power.      

Effect of Different Quantum Well Structures on the Output Power Performance of GaN-Based Light-Emitting Diodes

We investigated the effect of two different quantum well (QW) structures having different indium contents on the optical performance of fully packaged GaN-based light-emitting diodes (LEDs). Dual-spectrum QW LEDs exhibit ～4% higher external quantum efficiency (at 350 mA) than single-spectrum QW LEDs. However, the two types of LEDs exhibit similar efficiency droop behavior. For both types of LEDs, the output power decreases with increasing junction temperature. When the junction temperature exceeds 70°C, the dual-spectrum QW LEDs exhibit lower output power than the single-spectrum QW LEDs. The wavelength dependence of the output power (at 350 mA) of single-spectrum QW LEDs shows that the LEDs with shorter wavelengths experience more rapid optical degradation than the LEDs with longer wavelengths. Based on the wavelength- and junction-temperature-dependent output power, the droop behavior of the dual-spectrum QW LEDs is described and discussed.     

High efficiency integral III-N/II-VI blue-green laser converter

An integral optically-pumped laser converter comprising an ultra-low-threshold green (~540 nm) CdSe quantum dot laser chip pumped by a blue InGaN/GaN quantum well heterostructure laser grown on Si (111) substrates has been fabricated and studied. The maximum achieved quantum efficiency and pulse output power in green are as high as 14% and 3 W, respectively     

GaAs/InGaAs量子点探测器件微光读出研究

GaAs/InGaAs量子点光电探测器,在633 nm激光辐射3.5 nW条件下,器件偏压-1.4 V时,测得响应电流8.9×10-9A,电流响应率达到2.54 A/W,量子注入效率超过90%。基于GaAs/InGaAs量子点光电探测器的高量子注入效率、高灵敏度等特点,采用具有稳定的电压偏置,高注入效率和低噪声特点的CTIA(电容互阻跨导放大器)作为列放大器读出结构,输出部分采用相关双采样(CDS)结构去除系统和背景噪声。实验结果表明,在3.5 nW的微光辐射下,器件偏压为-2.5 V时,50μm×50μm像素探测器与读出电路互联后有7.14×107V/W的电压响应率。     

大功率半导体激光器光纤耦合模块的耦合光学系统

针对 8 0 8nm大功率 Ga As/ Ga Al As半导体量子阱激光器的远场光场分布特点 ,提出了与多模光纤耦合时对耦合光学系统的特殊要求 ,并根据低成本、实用化的要求设计制作了专用的耦合光学系统 ,对耦合光学系统的实际性能进行了测试 ,给出了耦合效率统计分布图、耦合偏差曲线和高低温可靠性实验结果 .用设计制作出的实用化耦合光学系统完成了输出功率 15— 30 W,光纤束数值孔径为 0 .11— 0 .2 2的半导体激光光纤耦合模块 ,模块的使用结果表明耦合光学系统稳定、高效、实用     

Characteristics of an erbium-doped fiber amplifier pumped by a frequency doubled diode-pumped Nd:YAG laser

The characteristics of an erbium-doped fiber amplifier pumped by a 532-nm diode-pumped Nd:YAG laser are presented. A maximum system gain of 31 dB at 591 Mb/s is obtained with a corresponding system noise of less than 0.5 dB. An amplified signal output power of greater than 10 mW was obtained, with a coupled pump power of 46 mW and a corresponding quantum efficiency of around 65%. By optimizing the erbium fiber design, higher system gains and saturation power levels are feasible. These figures, and in particular the combination of high output powers and low noise, establish the usefulness of this pump laser as a viable alternative to the semiconductor pump lasers currently under investigation at 1480 and 980 nm.<>     

Power conversion efficiency of quantum dot laser diodes

The power conversion efficiency of laser diodes with an array of quantum dots in the active region is analyzed. A model is proposed which allows analytical determination of the optimal cavity length corresponding to the highest conversion efficiency for a given output power. A comparison is made with experimental data for high-power lasers based on submonolayer quantum dots emitting at 0.94 μm. __________ Translated from Fizika i Tekhnika Poluprovodnikov, Vol. 34, No. 5, 2000, pp. 628–632. Original Russian Text Copyright ? 2000 by Zhukov, Kovsh, Mikhrin, Maleev, Odnoblyudov, Ustinov, Shernyakov, Kondrat’eva, Livshits, Tarasov, Ledentsov, Kop’ev, Alferov, Bimberg.