Offset quantum-well method for tunable distributed Bragg reflector lasers and electro-absorption modulated distributed feedback lasers

A two-section offset quantum-well structure tunable laser with a tuning range of 7 nm was fabricated using offset quantum-well inethod. The distributed Bragg reflector （DBR） was realized just by selectively wet etching the multiquantum-well （MQW） layer above the quaternary lower waveguide. A threshold current of 32 mA and an output power of 9 mW at 100 mA were achieved. Furthermore, with this offset structure method, a distributed feedback （DFB） laser was integrated with an electro-absorption modulator （EAM）, which was capable of producing 20 dB of optical extinction.

Wet Oxidation of AlxGa1-xAs/GaAs Distributed Bragg Reflectors

The wet oxidation of AlGaAs with high Al content in a distributed Bragg reflectors （DBR） is studied by scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. Some voids distribute along the oxide/GaAs interfaces due to the stress induced by the wet oxidation of the AlGaAs layers. These voids decrease the shrinkage of the Al2O3 layers to 8% instead of the theoretical 20% when compared to the unoxidized AlGaAs layers. With the extension of oxidation time, the reactants are more completely transported to the front interface and the products are more completely transported out along the porous interfaces. As a result,the oxide quality is better.

GaAs/GaInNAs多量子阱谐振腔增强型长波长光探测器

报道了一种具有高速响应特性的GaAs基长波长谐振强增强型(RCE)光探测器,它采用分子束外延技术(MBE)在GaAs衬底上直接生长GaAs/AlAs布拉格反射镜(DBR)和GaInNAs/GaAs多量子阱吸收层而形成,解决了GaAs系材料只能对短波长光响应的问题,实现了GaAs基探测器对长波长光的响应.该器件在峰值响应波长1 296.5 nm处获得了17.4%的量子效率,响应谱线半宽为11 nm,零偏置时的暗电流密度8.74×10-15 A/μm~2,具有良好的暗电流特性.通过RC常数测量计算得到器件的3 dB带宽为4.82 GHz.

VCSEL中布拉格反射体的电流机制和伏安特性

采用张弛法数值求解静电势的泊松方程,得出垂直腔面发射激光器(VCSEL)中N型和P型分布布拉格反射体(DBR)中一个周期单元的精确能带图.并以此为依据,从理论上分别分析和比较了多子漂移扩散、纯漂移和热电子发射电流机制所起的作用.指出由一对反对称同型异质结构成的DBR一个周期单元总是表现出欧姆性,但热电子发射电流机制的存在容易使每个结呈现整流特性,以致在电流输运过程中起主要作用的是其反向特性,导致偏压和电阻过大器件不能正常工作.但是漂移扩散机制具有明显欧姆性,在利用缓变DBR结构消除异质尖峰势垒之后漂移扩散机制将决定主要的电流输运.

VCSEL稳态热特性分析

使用数值方法对氧化层限制型垂直腔面发射激光器(VCSEL)内部稳态热场分布进行了计算,结果显示其分布形式取决于DBR区热导率及其与高阻限制层热导率的差异,并指出在限制层孔径变化及外加电极电压变化时对热场分布的影响;器件中温度最高的部分处于中心氧化限制层附近.有源层中温度沿径向的分布情况表明,在氧化限制孔径下方形成明显的温度台阶是导致器件有源层中产生折射率台阶的主要原因.

Self-aligned Coupled Waveguide Distributed Bragg Reflector Lasers

A novel self-aligned coupled waveguide (SACW) multi-quantum-well (MQW) distributed Bragg reflector (DBR) laser is proposed and demonstrated for the first time. By selectively removing the MQW layer and leaving the low SCH/SACW layer the Bragg grating is partially formed on this layer. By optimizing the thickness of the low SCH/SACW layer, a ～80% coupling efficiency between the MQW gain region and the passive region are obtained. The typical threshold current of the SACW DBR laser is 39 mA, the slope efficiency can reach to 0.2 mW/mA and the output power is more than 20 mW with a more than 30dB side mode suppression ratio.

利用边发射光致发光谱研究垂直腔面发射激光器材料的特性

在室温下测量了GaInP/AlGanInP垂直腔面发射激光器(VCSEL)的光致发光谱和反射谱，通过反射测量可以很容易得到激光器的腔模波长，但是用通常的背散射配置不能测得与有源区中量子阱有关的光致发光信号，用边激发配置可以测到量子阱的光致发光谱，但这样测得的光谱已经受到激光器中的分布布拉格反射镜(DBR)的调制。采用腐蚀去上DBR层的方法可以在背散射配置下测量子阱的光致光谱，但仍无法避免下DBR层对发光谱的调制作用，从而只有采用边激发-边发射模式才能测得VCSEL中量子阱的真实的光致发光谱。

Wavelength Tuning in Two-Section Distributed Bragg Reflector Laser by Selective Intermixing of InGaAp-InGaAsP Quantum Well Structure

The two-section tunable ridge waveguide distributed Bragg reflector (DBR) laser fabricated by the selective intermixing of an InGaAsP-InGaAsP quantum well structure is presented. The threshold current of the laser is 51mA. The tunable range of the laser is 4.6nm, and the side mode suppression ratio (SMSR) is 40dB.

镜面起伏对1.55 μm Si基MEMS光滤波器的影响

用传输矩阵方法，在简化的光学模型基础上，分别讨论了分布式Bragg反射镜DBR（Distributed Bragg Reflector）的生长精度及镜面起伏对1.55 μm Si基MEMS（Micro-Electro-Mechanical-System）可调谐光滤波器透射谱的影响。计算表明

Array for 980nm Vertical Cavity Surface Emitting Diodes and Detectors

Both the vertical cavity surface emitting diodes and detectors are fabricated by using the epitaxial wafer with resonant cavity structure. Their characteristics are analyzed. The light emitters have high spectral purity of 4.8nm and high electroluminescence intensity of 0.7mW while injection current is 50mA. A 1*16 array of surface emitting light device is tested on line by probes and then used for module. The light detectors have wavelength selectivity and space selectivity. The required difference in input mirror reflectivity between emitters and detectors can easily be achieved though varying the numbers of top DBR period by etching.

半导体微腔中电偶极子的自发发射

由于反射电场的影响，电偶极子在微腔中的自发发射速率不同于自由空间中的自发发射速率。本文采用镜像法计算了理想平面微腔、金属平面镜组成的半导体微腔和由分布布喇格反射镜(DBR)作为谐振腔的垂直发射激光器(VCSEL)中电偶极子的自发发射速率。计算结果表明

垂直腔面发射激光器中顶层相位对模式特性的影响

研究了垂直腔面发射激光器中不同的顶层厚度对激光器模式特性的影响。结果表明空气界面反射与分布布拉格反射器(DBR)的反射率反相时，将导致阈值增益增加几倍，而且模式光场强度在出射端面有反常的增强，但对光场进入分布布拉格反射器的等效厚度影响不大。精确腐蚀顶层厚度可代替调节分布布拉格反射器周期数，以改善器件特性。

外加电场下垂直腔面发射激光器的偏振转换电流（英文）

计算了作用在垂直腔面发射激光器(VCSEL)的上面的分布喇格反射镜(DBR)上的外加电场产生的双折射，并在此基础上通过对自旋反转模型(SFM)的修正，得到面发射激光器在外加电场存在时的偏振转换电流。

InGaAs/GaAs多量子阱 SEED面阵结构特性与设计（英文）

讨论了谐振腔中的DBR对InGaAs/GaAs多量子阱SEED面阵光反射特性的影响。采用InGaAs/GaAs作为多量子阱SEED器件的有源区，从而获得了980nm工作波长。设计和分析了InGaAs/GaAs多量子阱SEED中的一种用于倒装焊的新型谐振腔结构。多量子阱材料是用MOCVD系统生长，利用微区光反射谱、PL谱以及X射线双晶衍射对多量子阱材料进行了测量和分析，测量结果表明多量子阱材料具有良好的质量，证明了器件结构的设计和分析是准确的。

X射线双晶衍射在分布布喇格反射镜研制中的应用

利用X光双晶衍射的动力学理论对垂直腔面发射激光器(VCSEL)的分布布喇格反射镜(DBR)的特性曲线进行了模拟研究。从中得到DBR AlAs/Al_xGa_(1-x)As的厚度及组分x值,应用所得到的这些数值进行光学薄膜反射谱的模拟计算,并与实验所测得的DBR反射谱进行比较,得到了证实。应用这套方法指导VCSEL外延片的生长,获得了良好的结果。