1.3μm GaAs基量子点垂直腔面发射激光器结构设计与分析

结合垂直腔面发射激光器（VCSEL）原理以及量子点增益特点，计算了不同结构VCSEL的腔内损耗和量子点的模式增益.分析了激光器阈值特性以及氧化限制层对光损耗的影响.设计了含 氧化限制层的13μm量子点VCSEL结构. 关键词： 量子点 垂直腔面发射激光器 增益     

适用于量子阱激光器的速率方程

首次在理论上用量子阱激光器增益与载流子密度的对数关系替代了原有速率方程中的线性关系，得到了改进了速率方程，分析了稳态和调制特性，从理论上得到了获得最低阈值的最佳阱数和最大调制带宽的最佳腔长。     

用直接模拟法分析量子阱半导体激光器瞬态响应

根据光增益与载流子密度的对数关系 ,通过适应于多量子阱激光器的速率方程的直接模拟分析 ,得到了注入电流、阱数和腔长对多量子阱激光器的激射阈值、开关延迟时间、弛豫振荡频率和光输出等参量之间的依赖关系 .运用相图确立了在瞬态过程中 ,载流子数密度和光子数密度之间的转化过程 .从而为改善量子阱激光器的高频调制特性以及优化设计器件结构参数提供了理论依据     

亚毫安阈值的1.3μm垂直腔面发射激光器

设计并研制了室温连续工作的单模13 μm垂直腔面发射激光器（VCSEL）,阈值电流为051 mA,最高连续工作温度达到82℃,斜率效率为029 W/A.采用InAsP/InGaAsP应变补偿多量子阱作为有源增益区,由晶片直接键合技术融合InP基谐振腔和GaAs基GaAs/Al（Ga）As分布布拉格下反射腔镜,并由电子束蒸发法沉积SiO₂/TiO₂介质薄膜上反射腔镜形成13 μm VCSEL结构.讨论并分析了谐振腔模式与量子阱增益峰相对位置对器件性能的影响. 关键词： 垂直腔面发射激光器 晶片直接键合 应变补偿多量子阱     

用直接模拟法分析量子阱半导体激光器瞬态响应

根据光增益与载流子密度的对数关系,通过适应于多量子阱激光器的速率方程的直接模拟分析,得到了注入电流、阱数和腔长对多量子阱激光器的激射阈值、开关延迟时间、弛豫振荡频率和光输出等参量之间的依赖关系.运用相图确立了在瞬态过程中,载流子数密度和光子数密度之间的转化过程.从而为改善量子阱激光器的高频调制特性以及优化设计器件结构参数提供了理论依据.     

外腔半导体激光器中反馈耦合系数及介持吸收系数的测量

在室温下研究了外腔反馈对ＧａＡｌＡｓ量子阱半导体激光器阈值的影响，提出了测量实际反馈量及半导体激光器增益介质吸收系数的方法。利用所测反馈系数汲阈值得到了反馈耦合因子ｋ，驱动电流和增益之间的系数ζ以及实验所用半导体激光器增益介质的吸收系数。     

高功率垂直外腔面发射半导体激光器增益设计及制备

垂直外腔面发射半导体激光器(vertical external cavity surface emitting laser, VECSEL)兼具高功率与良好的光束质量,是半导体激光器领域的持续研究热点之一.本文开展了光抽运VECSEL最核心的多量子阱增益区设计,对量子阱增益光谱及其峰值增益与载流子浓度及温度等关系进行系统的理论优化,并对5种不同势垒构型的量子阱增益特性进行对比,证实采用双侧GaAsP应变补偿的发光区具有更理想的增益特性.对MOCVD生长的VECSEL进行器件制备,实现了VECSEL在抽运功率为35 W时输出功率达到9.82 W,并且功率曲线仍然没有饱和;通过变化外腔镜的反射率, VECSEL的激光波长随抽运功率的漂移系数由0.216 nm/W降低至0.16 nm/W,证实外腔镜反射率会影响VECSEL增益芯片内部热效应,从而影响VECSEL激光输出功率.所制备VECSEL在两正交方向上的发散角分别为9.2°和9.0°,激光光斑呈现良好的圆形对称性.     

基于两端自发荧光辐射的808nm半导体激光器增益偏振特性实验表征和能带分析

通过半导体激光器两端的放大自发荧光辐射可以获取器件的光学增益信息. 本文利用这一新的增益实验测量方法, 开展了对连续运行的808nm GaAs/AlGaAs量子阱激光器横向电场 (TE)与磁场(TM)偏振增益特性的实验研究. 通过将实验结果与理论增益曲线对比, 分析了非应变GaAs量子阱TE和TM极化偏振对应的空穴子能带随注入电流的变化规律, 以及激光器在连续运行状态下的实际增益状态和影响因素. 关键词： 半导体激光器 增益测量 偏振 量子阱和能带     

高速调制响应垂直腔面发射激光器中的微腔效应

应用微腔物理和量子阱物理，计算了量子阱垂直腔面发射激光器的自发发射谱和自发发射寿命，通过对半导体激光器传输函数的研究，发现缩短自发发射寿命是垂直腔面发射激光器实现高速调制响应的主要原因.     

应变量子阱激光器阱宽与组分的确定和增益特性的理论研究

本文根据一维势阱和应变效应的简单理论,给出一种既简单又较准确的确定量子阱的组分和阱宽的方法。并且,针对较为常用的波长为1.3μm的InGaAs/InGaAsP材料以及最新兴起的InAsP/In材料应变量子阱激光器,利用该方法得到了组分和量子阱阱宽。再根据这些参数,利用变分法计算了量子阱的能带结构和二维电子气状态密度。然后,在选取不同的线形函数的情况下分别计算了对应于不同的注入载流予浓度时的这两种激光器的线性增益和微分增益。     

光子晶体激光器阈值特性的理论研究

针对光子晶体激光器的结构特点,并考虑到非辐射复合及增益饱和效应的影响,运用速率方程研究了光子晶体激光器的阈值特性。由爱因斯坦A、B系数的关系,得出了自发辐射耦合因子的变化并不独立于腔体积的结论,并给出其具体数学表达式。分析了自发辐射耦合因子、表面复合速率、有源区体积及品质因子对光子晶体激光器阈值电流的影响。结果表明,经过优化处理,可以较好地降低光子晶体激光器的阈值电流,为无阈值激光器的实现提供了理论依据。     

Velocity of pulse propagation in media with amplitude nonlinearity

The propagation velocity of optical wave fronts can be accelerated by the influence of gain saturation. We report systematic measurements for the specific case of Brillouin gain in optical fibers. A simplified analytic rate equation approach permits a qualitative understanding of the observations in terms of a pure amplitude nonlinearity. We point out that there is a close analogy to a mode-locked laser with gain saturation. Pursuing this analogy, we can explain why the changes in propagation velocity are hardly measurable for synchronously pumped lasers, but easily amount to several percent for amplifiers or lasers based on stimulated Brillouin scattering.     

Analysis of linewidth enhancement factor for compressively strained AlGaInAs and InGaAsP quantum well lasers

We have compared and analyzed theoretical investigation for the possibility of extreme reductions in the linewidth enhancement factor (??-factor) in strained layer quantum-well (QW) lasers between AlGaInAs and InGaAsP material. Valence band effective masses and optical gain in both types of QW lasers under compressive strain have been calculated using 4 ×?4 Luttinger?CKohn Hamiltonian. We have used Kramers?CKronig relations to calculate the refractive index change due to carrier induced. The ??-factor was up to 1.61 times smaller in AlGaInAs QW than in InGaAsP QW laser. The material differential modal gain and carrier induced refractive index change was found to be approximately 1.38 times larger and 1.15 times smaller respectively, in the previous material QW than in the latter QW laser. We also compared our results to the previously reported results for both QWs lasers.     

(001)和(111)取向的张应变量子阱光学特性的比较

以(001)和(111)价带Lutinger-Kohn哈密顿量为基础,讨论了这两种取向的量子阱的能带结构、态密度(DOS)、跃迁矩阵元和增益特性。由于材料结构的各向异性,(111)取向的量子阱在平行生长面内有较小的重空穴有效质量,无应变和压应变激光器可以很好地利用这一点。而(001)取向的量子阱虽有较小的平面内轻空穴有效质量,但并不比(111)量子阱的小多少;加上(001)量子阱的价带耦合效应强,使其DOS比(111)量子阱的大,在相同载流子注入下,张应变(111)量子阱的增益系数比相应(001)量子阱的要高。所以张应变(111)量子阱激光器仍然比相应的(001)量子阱激光器性能要好。可以认为匹配和压应变的(111)激光器优异的性能不仅来自小的面内有效质量,也来自于弱的价带耦合效应。     

光纤光栅的温度增敏实验

用热膨胀系数较大的聚合物材料对光纤光栅进行封装处理,极大地提高了光纤光栅的温度灵敏度。我们将光纤光栅封装于两种不同的聚合物材料中,其温度灵敏度分别提高6倍和23倍之多。这是迄今有文献报道的最大的光纤光栅温度灵敏度。     

Properties of laser gain of Li:CdZnO/ZnMgO quantum well

The many-body optical gain in Li:CdZnO/MgZnO quantum well (QW) structures with spontaneous polarization and piezoelectric polarization, and ferroelectric dipole moment is investigated by using the non-Markovian gain model with many-body effects. The CdZnO/MgZnO QW structure with high Cd composition is found to have smaller optical gain because the strain-induced piezoelectric polarization and the spontaneous polarization in the well increase with the inclusion of Cd. The internal field is reduced due to the additional polarization by Li in the CdZnO/MgZnO QW structure. These results show that Li:CdZnO-based QW lasers are promising candidates for optoelectric applications in visible and UV regions.     

The effects of carrier dependant nonlinear gain on quantum well VCSEL characteristics

In this paper, we present a numerical opto-electro-thermal model for studying vertical cavity surface emitting lasers operation. The model is applied to an index-guided structure with an oxide aperture and multiple quantum-wells in active layer. The interdependent process of carrier transport, heat generation and optical field are solved self-consistently using finite difference time domain in cylindrical system. The gain of quantum wells (QWs) is calculated based on the solution of Schrödinger equation considering heavy hole-light hole band-mixing effect. The calculated maximum gain versus injected carriers is fitted by a 3th order polynomial function and used in opto-electro-thermal model. The inclusion of QW maximum gain calculation for constant wavelength in the model allows us to study threshold current value and higher order transverse modes as well as their dependencies on variation of gain and refractive index induced by carrier and heat more accurately than linear gain approximation. The results show a lower threshold current compared with linear gain approximation. For injection current above the threshold, we consider the spatial hole burning, thermal lensing and self focusing effects.