大功率半导体激光器腔面镀膜的理论研究

从平面波假设出发推导了多层薄膜的特性矩阵，得到了膜系的反射率计算公式。研究了腔面反射率对大功率半导体激光器的外量子效率、阈值增益和输出功率比的影响，并给出了整个膜系反射率随膜层的光学厚度、折射率差及其层数的变化趋势。该模型对半导体激光器的腔面膜层设计具有实际的指导意义。     

基于量子级联激光器的中远红外高反射率测量

利用光腔衰荡技术开展了中远红外波段的高反镜反射率测量研究.以中心波长9.7μm附近的脉冲量子级联激光器为光源,构建了高反射率测量实验装置.利用该装置对不同腔长下腔镜的反射率进行了测量,最终测定其反射率为99.9464%,测量重复性误差优于0.0014%.实验表明该测量装置重复性精度高,可用于中远红外高反镜反射率的精确测量.     

“量子级联”激光器

“量子级联”激光器普通半导体激光器受化学结构制约，它大约以相当于导带价带差的能量向外辐射，因而不能发射中远红外范围的光。过去，为获得新的波长，人们在研制新的半导体合金上动了相当大的脑筋。而现在，美国电话电报公司贝尔实验室ＦｅｂｄｒｉｃｏＣａｐａｓｓｏ...     

分布反馈量子级联激光器的光栅制备

利用全息曝光方法制备了分布反馈量子级联激光器的光栅掩模,选择和发展了恰当的用于InGaAs/InP材料的光栅腐蚀优化工艺,得到腐蚀规律,讨论了腐蚀机制。在量子级联激光器的InGaAs/InP层上制备光栅得到分布反馈量子级联激光器,其单模特性较好,信噪比大于30dB。     

808nm半导体激光器的腔面反射率设计

通过对不同腔长的808nm半导体激光器单管进行P-I测试,提取出了材料内部参数,如内量子效率,内损耗、透明电流密度、模式增益等.根据得出的内部参数进行了腔面反射率设计,分析腔面反射率与功率转换效率的关系,得出了关系曲线.进行腔面镀膜实验,把实验值与计算值相比较,二者相吻合.通过这种腔面反射率设计方法,可以得到半导体激光器的最大功率转换效率,从而使其工作于优化状态下.     

THz量子级联激光器的材料生长和器件制作

采用分子束外延的方法，生长了GaAs／Al0.17Ga0.85As基共振声子辅助跃迁的太赫兹量子级联激光器结构，并按照单面金属波导的工艺进行了器件制作。材料的结构由高分辨X射线衍射来确定。在温度为9-150K的范围内，测量了器件的I-V曲线。     

亚毫安室温连续工作InGaAs垂直腔面发射激光器

报道了ＩｎＧａＡｓ应变量子讲垂直腔面发射激光器（ＶＣＳＥＬ）的室温连续工作。在ＭＢＥ生长过程中利用红外高温仪测量了表观衬底热辐射振荡，实现了原位厚度监测；采用阶梯型分布布拉格反射器（ＤＢＲ）及腐蚀倒台面结构，降低了器件串联电阻。对于２×３μｍ２的台面结构ＶＣＳＥＬ，室温连续工作阈值电流一般为１．５ｍＡ，最低达到０．７ｍＡ，阈值电压为２．５伏，输出功率达到０．５ｍＷ，激射波长为０．９４ｕｍ，量子效率为１２％。     

GaAs／GaAlAs低阈值垂直腔面发射激光器

通过对增益波导型ＧａＡｓ／ＧａＡｌＡｓ垂直腔面发射激光器的材料生长和工艺制作的研究，实现了在室温下的脉冲激射。其激射阈值电流低达１０ｍＡ，输出光功率不低于０．３ｍｗ，有的可达０．７ｍｗ以上，器件单横模、单纵模工作，线宽小于４人。     

半导体激光器后腔面高反射涂层的研究

采用金属银(Ag)做为高反射镀膜材料，ZrO2介质膜作为与激光器端面的绝缘层和Ag保护膜，在激光器后腔面实现了高反射涂层。经激光器光电特性测试表明，该高反射膜系能使激光器输出功率提高60％，阈值电流减小20％～50％，并且具有良好的化学稳定性、热稳定性和机械强度，能有效保护半导体激光器后腔面。     

太赫兹量子级联激光器波导数值模拟

采用传输矩阵法(TMM)计算比较了太赫兹量子级联激光器两种波导限制方式(单面等离子波导和双面金属波导)的特点.结果表明双面金属波导的限制因子较单面等离子波导的限制因子有明显的提高,具有良好的模式限制作用,可以有效地降低波导层的厚度.     

Nonlinear optical interactions of laser modes in quantum cascade lasers

We overview the results of recent experimental and theoretical studies of nonlinear dynamics of mid-infrared quantum cascade lasers (QCLs) associated with nonlinear interactions of laser modes. Particular attention is paid to phase-sensitive nonlinear mode mixing which turns out to be quite prominent in QCLs of different kinds and which gives rise to frequency and phase locking of laser modes. Nonlinear phase coupling of laser modes in QCLs leads to a variety of ultrafast and coherent phenomena: synchronization of transverse modes, beam steering, the RNGH multimode instability, and generation of mode-locked ultrashort pulses.     

Approximate analytical expressions for pulse modulation response of quantum cascade lasers

Approximate analytical expressions for turn-on delay, rise time and fall time for pulse modulation of the drive current of quantum cascade lasers are presented. These time expressions are obtained using piece-wise analysis of rate equations. From the analytical expressions, the effects of laser parameters and off and on currents are discussed. A numerical analysis shows reasonable agreement with analytical results. It also confirms the predictions from analytical results. The pulse response is compared with that of near-infrared interband lasers.     

Auger recombination rate in quantum well lasers

Auger recombination is the dominant non-radiative process in InGaAsP quantum well lasers and is responsible for the poor temperature dependence of the threshold current density. In all recent calculations of the Auger rate the electron-electron interaction potential is taken to be either of the bulk form or an approximate form derived from it. In the present work, the rate is calculated by taking an appropriate potential valid for quasi two-dimensional electrons and the expected changes are pointed out. The calculated Auger life-time is in agreement with the values reported in the literature.     

Semiconductor lasers for optical communication

Recent progress in the development of semiconductor lasers for optical-fibre communication is reviewed. GaInAsP buried heterostructure and distributed feedback structure, are described in some detail. An overview of the novel GaInAsSb mid-infrared (2–4 microns) lasers is also presented.     

Polarisation behaviour of diode lasers with frequency selective feedback

The paper reviews recent results obtained with diode lasers used in external hybrid cavities with frequency selective feedback. Such cavities attract continuing interest for several reasons. They generate a tunable single laser mode with very low linewidths (usually a few tens of kilohertz). Very wide discrete tunable ranges over 100 nm for Fabry-Perot type and over 200 nm for quantum well lasers are achieved. They can be made to oscillate in a tunable mode having the desired polarization state,TE orTM and, in some cases, simultaneously atTE andTM. This is done by designing a cavity that increases strongly theTM/TE intensity ratio and by using coatings on one laser facet that greatly lower bothTE andTM reflectivities. High-speed polarization switching in the gigahertz range is possible by inserting passive or active polarization selecting elements in the cavity. For all these reasons hybrid external cavities are attractive for applications in optical metrology, spectroscopy and optical communications. Moreover, the external cavity configuration allows the study of physical mechanisms in the laser diode by inducing on purpose phenomena that would have been otherwise impossible to achieve with free-running lasers.