A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well vertical-cavity surface-emitting laser

A low-threshold and high-power oxide-confined 850-nm AlInGaAs strained quantum-well (QW) vertical-cavity surface-emitting laser (VCSEL) based on an intra-cavity contacted structure is fabricated. A threshold current of 1.5 mA for a 22 μm oxide aperture device is achieved, which corresponds to a threshold current density of 0.395 kA/cm². The peak output optical power reaches 17.5 mW at an injection current of 30 mA at room temperature under pulsed operation. While under continuous-wave (CW) operation, the maximum power attains 10.5 mW. Such a device demonstrates a high characteristic temperature of 327 K within a temperature range from -12℃ to 96℃ and good reliability under a lifetime test. There is almost no decrease of the optical power when the device operates at a current of 5 mA at room temperature under the CW injection current.     

注入电流引起质子轰击VCSEL中的模式竞争

为了分析质子轰击垂直腔面发射激光器(VCSEL)中注入电流引起的激光模式竞争过程,在三维空间中对VCSEL激射后光电热进行了研究。给出仿真光电热的方程之后,在室温连续工作条件下,对电流孔半径r为4μm、阈值电流Ith为4.5 m A的VCSEL进行自洽求解。当注入电流Iin分别为5.0,5.5,6.0 m A时,得到了对应的外加电压和输出光功率,并绘制了VCSEL的电势、注入电流、载流子、光场和热场的空间分布,给出了连续工作下输出光功率随注入电流变化的曲线。仿真结果表明:随着注入VCSEL中的电流增加,电流密度增大,激光的横向基模和横向一阶模式同时增强。横向一阶模式增加的强度及扩展的范围大于横向基模,激光输出能量逐渐向横向一阶模式过渡,横向模式竞争的同时产生载流子空间烧孔,因此在电流孔半径r≥4μm的VCSEL中,连续工作激光模式不稳定。     

Low threshold current density, low resistance oxide-confined VCSEL fabricated by a dielectric-free approach

We present the fabrication process and experimental results of 850-nm oxide-confined vertical cavity surface emitting lasers (VCSELs) fabricated by using dielectric-free approach. The threshold current of 0.4 mA, which corresponds to the threshold current density of 0.5 kA/cm², differential resistance of 76 Ω, and maximum output power of more than 5 mW are achieved for the dielectric-free VCSEL with a square oxide aperture size of 9 μm at room temperature (RT). L–I–V characteristics of the dielectric-free VCSEL are compared with those of conventional VCSEL with the similar aperture size, which indicates the way to realize low-cost, low-power consumption VCSELs with extremely simple process. Preliminary study of the temperature-dependent L–I characteristics and modulation response of the dielectric-free VCSEL are also presented.     

Oxide-apertured VCSEL with short period superlattice

Novel distributed Bragg reflectors (DBRs) with 4.5 pairs of GaAs/AlAs short period superlattice (SPS)used in oxide-apertured vertical-cavity surface-emitting lasers (VCSELs) were designed. The structure of a 22-period Al0.9Ga0.1As (69.5 nm)/4.5-pair [GaAs (10 nm)-AlAs (1.9 nm)] DBR was grown on an n+ GaAs substrate (100) 2° off toward (111)A by molecular beam epitaxy. The emitting wavelength was 850 nm with low threshold current of about 2 mA, corresponding to the threshold current density of 2 kA/cm2. The maximum output power was more than 1 mW. The VCSEL device temperature was increased by heating ambient temperature from 20 to 100 ℃ and the threshold current increased slowly with the increase of temperature.     

A novel structure of visible semiconductor lasers

Terraced substrate inner current stripe lasers emitting in the range of 750–780 nm are developed with very simple fabrication processes. The lasers have good performance of cw room temperature, linear light-current output over 30 mW per facet and maintain stable fundamental transverse and longitudinal mode of 2–4 times current threshold. The current threshold of 25 mA under cw room temperature operation has been achieved.     

808 nm垂直腔面发射激光器列阵的温度特性分析

为了研究温度对808 nm InGaAlAs垂直腔面发射激光器（VCSEL）列阵输出特性的影响,通过变温塞耳迈耶尔方程计算了InGaAlAs量子阱VCSEL的温度漂移系数。采用非闭合环结构,制备了2×2 的808 nm垂直腔面发射激光器列阵,每个单元的出光口径为60 μm。通过热沉温度调节,对不同温度下的列阵激射波长、光功率以及阈值电流进行了测量。在温度为20 ℃、脉宽为50 μs、重复频率为100 Hz的脉冲条件下,列阵的最大输出功率达到56 mW,中心光谱值为808.38 nm,光谱半宽为2.5 nm,连续输出功率达到22 mW。通过变温测试,发现输出功率在50 ℃以上衰减剧烈,列阵的温漂系数为0.055 nm/℃。实验测得的温漂系数与理论值保持一致。     

V型槽衬底内条形大光腔可见光半导体激光器

采用一种新的液相外延工艺，研制出具有大光腔结构的Ｖ型槽衬底内条形可见光发射半导体激光器，其光谱波长为７７９－７８４ｎｍ，室温连续工作阈值电流为６０ｍＡ，具有２倍阈值的基模工作时，线性输出光功率可达８ｍＷ，４ｍＷ下工作寿命已超过３０００小时。     

AlInGaAs/AlGaAs垂直腔面发射激光器温度特性的对比研究

通过测量、对比材料生长和器件制备条件基本相似，但是谐振腔腔模波长与增益峰值波长相对位置明显不同的两类氧化物限制型应变AlInGaAs/AlGaAs量子阱垂直腔面发射激光器(VCSEL)在261—369K温度范围内输出光功率-电流的变温曲线，同时结合测试得到的两类样品的白光反射谱、光荧光谱以及模拟计算得到的不同温度下VCSEL反射谱和增益谱，分析了输出光功率、阈值电流、斜率效率和激射波长随温度变化的关系，掌握了新材料AlInGaAs的温度特性，得到了谐振腔腔模波长和增益峰值波长的相对位置对VCSEL输出特性，尤其是对阈值的影响规律，指出获得室温工作阈值最低且稳定的VCSEL的一个方法是调整谐振腔腔模波长和增益峰值波长的相对位置，并利用这种方法获得了特征温度T₀=333K的AlInGaAs/AlGaAs量子阱VCSEL器件. 关键词： AlInGaAs 垂直腔面发射激光器 特征温度     

894nm高温垂直腔面发射激光器及其芯片级铯原子钟系统的应用

报道了自行研制的894 nm高温垂直腔面发射激光器(VCSEL)以及基于此类器件的芯片级铯原子钟系统的应用实验结果.根据芯片级铯原子钟对VCSEL在特定高温环境下产生894.6 nm线偏振激光的要求,对器件的量子阱增益及腔模位置等材料结构参数进行了优化,确定增益-腔模失谐量为-15 nm,使器件的基本性能在高温环境下保持稳定.研制的VCSEL器件指标为:20—90?C温度范围内阈值电流保持在0.20—0.23 m A,0.5 m A工作电流下输出功率0.1 mW;85.6?C温度环境下激光波长894.6 nm,偏振选择比59.8:1;采用所研制的VCSEL与铯原子作用,获得了芯片级铯原子钟实施激光频率稳频的吸收谱线和实施微波频率稳频的相干布居囚禁谱线.     

高速850 nm垂直腔面发射激光器的优化设计与外延生长

利用传输矩阵理论和TFCalc薄膜设计软件分析了分布布拉格反射镜和垂直腔面发射激光器(VCSEL)的反射率谱特性,对比了从谐振腔入射与从表面入射时反射率谱的差异,为白光反射谱表征VCSEL外延片提供了依据.利用Crosslight软件模拟了InGaAs/AlGaAs应变量子阱的增益谱随温度的变化特性及VCSEL器件内部温度分布,设计了增益-腔模调谐的VCSEL.采用金属有机物化学气相淀积设备外延生长了顶发射VCSEL,制作了氧化孔径为7.5μm的氧化限制型VCSEL器件,测试了器件的直流特性、光谱特性和眼图特性;6 mA,2.5 V偏置条件下输出光功率达5 mW,4级脉冲幅度调制传输速率达50 Gbit/s.     

Metal-clad ridge waveguide structure InGaP/InGaAIP visible laser diodes

InGaP/InGaAIP visible-light laser diodes with a metal-clad ridge waveguide structure have been fabricated. Compressively strained SCH-MQW structures were grown by low-pressure MOCVD and the lasing wavelength was 690 nm. The threshold current was 28 mA at 25°C for a 400 m cavity and 5 m stripe width. CW operation was obtained as the cleaved device by employing thick gold layer as a heat spreader. The light-output power versus CW current was linear up to a maximum light output power of 38 mW. Stable operation of the fundamental transverse optical mode was maintained up to 30 mW. These results show that this metal-clad ridge waveguide structure provides sufficient current confinement even under high light output power operation.     

Improved efficiency of GaAs-based VCSEL by utilizing fan-pad metallization and trench patterning

Emphasizing the Vertical-Cavity Surface-Emitting Laser (VCSEL) device packaging, fan-pad metallization and trench patterning are demonstrated for VCSEL operating at 850 nm of the electromagnetic spectrum. The fabricated devices are observed to exhibit low threshold current and series resistance, contributing thereby to higher VCSEL efficiency. It is also observed that the output spectral characteristics of the fabricated device show stable multimode operation. The results indicate that the proposed VCSEL packaging exhibits superior device performance as compared to the VCSEL device packaged with square-pad metal.     

GaAlAs/GaAs非均匀阱宽多量子阱超辐射发光管材料制备及表征

超辐射发光二极管(SLD)具有不同于半导体激光器和普通发光二极管的优异性能。为了制备高功率半导体超辐射发光管,并且得到比较大的光谱宽度、大的单程增益和抑制电流饱和,我们研究设计了具有850nm辐射波长的GaAlAs/GaAs非均匀阱宽多量子阱超辐射发光二极管结构,采用分子束外延(MBE)方法进行了材料制备。同时利用X射线双晶衍射,变温(10～300K)光致发光(PL)等方法检测分析了外延薄膜的结构和光电特性。在光致发光谱线中我们得到了发射波长850nm的谱峰,谱峰范围跨跃800～880nm,双晶回摆曲线结果显示了设计的结构得到实现。在注入电流140mA时,器件输出光谱的半峰全宽可以达到26nm,室温下连续输出功率达到6mW。     

Stable single-mode operation of 894.6 nm VCSEL at high temperatures for Cs atomic sensing

In this paper, stable single-mode operation at high temperatures is produced by the surface-relief-integrated vertical cavity surface emitting laser(VCSEL). The gain-cavity mode detuning technique is employed to realize high operating temperatures for the VCSEL. The surface relief is etched in the centre of the top side as a mode discriminator for the fundamental mode output, and the threshold current minimum is 1.94 mA at high temperatures by the gain-cavity mode detuning technique. Maximum single-fundamental-mode output power of 0.45 mW at 80℃ is obtained, and the side mode suppression ratios(SMSRs) are more than 30 dB with increasing temperature and current, respectively.     

Optimization of electro-optical characteristics of GaAs-based oxide confinement VCSEL

An experimental study has been presented of the oxide-confined vertical-cavity surface-emitting lasers (VCSEL) operating in the 850 nm region of the electromagnetic spectrum. In this regard, various relevant VCSEL samples with numerous oxide aperture sizes have been fabricated and characterized. Thorough investigations of the electrical as well as optical characteristics of the fabricated samples have been performed which includes the overall device performance as a function of the oxidize aperture sizes. It is reported that the VCSEL with oxide aperture size <10 μm require low threshold currents (<1 mA). Further, the differential quantum efficiencies up to 28% were measured for a number of these devices. It is found that devices employing oxide aperture of 10 to 15 μm shows promising electro-optical characteristics for 850 nm oxide VCSEL optimization.     

Single-mode low threshold current multi-hole vertical-cavity surface-emitting lasers

A multi-hole vertical-cavity surface-emitting laser (VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-reflector of an oxidation-confined 850 nm VCSEL. The single-mode output power of 2.6 mW, threshold current of 0.6 mA, full width of half maximum lasing spectrum of less than 0.1 nm, side mode suppression ratio of 28.4 dB, and far-field divergence angle of about 10° are obtained. The effects of different hole depths on the optical characteristics are simulated and analysed, including far-field divergence, spectrum and lateral cavity mode. The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter-hole spacing and the scattering loss at the bottom of the holes, particularly for higher order modes.     

低压MOCVD生长GaN p—n结蓝光LED

简要报道了采用一种改进的低压金属有机化物化学气相沉积（ＬＰ－ＭＯＣＶＤ）方法制备ＧａＮｐ－ｎ结蓝光光发射二极管（ＬＥＤ），介绍了ＬＥＤ的基本特性，这种ＬＥＤ具有良好的Ｉ－Ｖ特性和光谱特性，室温下，在正向电压５Ｖ，正向电流３－２０ｍＡ的条件下，峰值波长为依Ｍｇ的掺杂浓度和退火条件的不同而不同，分别在４２５ｎｍ，４３５ｎｍ和４８０ｎｍ附近，发射谱的半峰宽约为５０ｎｍ。     

Single-mode low threshold current multi-hole vertical-cavity surface-emitting lasers

A multi-hole vertical-cavity surface-emitting laser(VCSEL) operating in stable single mode with a low threshold current was produced by introducing multi-leaf scallop holes on the top distributed Bragg-reflector of an oxidationconfined 850 nm VCSEL.The single-mode output power of 2.6 mW,threshold current of 0.6 mA,full width of half maximum lasing spectrum of less than 0.1 nm,side mode suppression ratio of 28.4 dB,and far-field divergence angle of about 10 are obtained.The effects of different hole depths on the optical characteristics are simulated and analysed,including far-field divergence,spectrum and lateral cavity mode.The single-mode performance of this multi-hole device is attributed to the large radiation loss from the inter-hole spacing and the scattering loss at the bottom of the holes,particularly for higher order modes.     

Homojunction-structured ZnO light-emitting diodes fabricated by dressed-photon assisted annealing

We formed a p?Cn homojunction by implanting nitrogen ions, serving as a p-type dopant, into an n-type ZnO crystal. A forward bias current was injected into the crystal while irradiating it with light, bringing about Joule heating which annealed the crystal and changed the spatial distribution of the N-dopant concentration. This activated the N-dopant, causing its concentration distribution to be modified in a self-organized manner so as to be suitable for generating dressed photons. A light-emitting diode fabricated by this dressed-photon assisted annealing method showed electroluminescence at room temperature. In a device fabricated by annealing under irradiation with 407 nm-wavelength light, at a forward bias current of 20 mA, the peak wavelength of the electroluminescence was 436 nm, the optical output power was 6.2 ??W, and the external quantum efficiency was 1.1×10^?4. The emission spectral profile depended on transitions from intermediate phonon states.     

1.55-μm InGaAs/InGaAlAs MQW vertical-cavity surface-emitting lasers with InGaAlAs/InP distributed Bragg reflectors

High-performance InGaAs/InGaAlAs multiple-quantum-well vertical-cavity surface-emitting lasers (VCSELs) with InGaAlAs/InP distributed Bragg reflectors are proposed for operation at the wavelength of 1.55 μm. The lasers have good heat diffusion characteristic, large index contrast in DBRs, and weak temperature sensitivity. They could be fabricated either by metal-organic chemical vapor deposition (MOCVD) or by molecular beam epitaxy (MBE) growth. The laser light-current characteristics indicate that a suitable reflectivity of the DBR on the light output side in a laser makes its output power increase greatly and its lasing threshold current reduce significantly, and that a small VCSEL could output the power around its maximum for the output mirror at the reflectivity varying in a broader range than a large VCSEL does.