本论文对增益耦合型（Gc）分布反馈（DFB）激光器／电吸收型调制器单片集成光源器件进行了理论和实验研究。 首先，通过理论计算比较了分别采用增益耦合型、γ/4相移（QWS）型和普通折射率耦合（IC）型DFB激光器作为光源部分的DFB激光器／电吸收型调制器单片集成光源器件的单模选择能力、调制频移和单端光输出效率等特性，得知GC型器件的调制频移特性与IC及QWS型器件基本相同，但GC型器件的单模成品率要高得多，特别在高反／抗反镀膜情况下，单端光输出效率大为提高。基于以上优点，并考虑到GC型器件无需制作相移光栅而带来的工艺简化，本论文指出增益耦合型DFB激光器／电吸收型调制器单片集成光源是极有前途的光通信用理想光源。 本论文给出了在外加电场下量子阱吸收系数的计算方法，提出了一种新的量子阱调制器优化设计方法，对GaAIAs／GaAs材料量子阱波导调制器进行了优化设计，并对GaAIAs／GaAs量子阶材料的电吸收特性进行了实验研究。在国内首次成功地制作了用于光通信的InGaAs／InAIAs量子阱电吸收型波导调制器，作为初步结果，器件在2V的调制电压下达到了7dB的调制深度。 本论文对GaAIAs／GaAs多量子阱增益耦合型DFB激光器进行了理论设计，在设计中重点对吸收光栅的占空比和厚度进行了优化，作为增益耦合型DFB激光器制作的预备实验，首先制作了GaAIAs／GaAs多量子阱分别限制结构激光器，阈值电流密度约2000A／cm2。利用GaAIAs／GaAs的选择性热腐蚀特点，开发出一种吸收光栅上MBE外延的新工艺，同时获得了精确控制的光栅形状和清洁的生长界面。采用这种新工艺，在国际上首次成功地制作了完全MBE生长的GaAIAs／GaAs多量子阱增益耦合型DFB激光器，这也是我国首次制作成功的增益耦合型DFB激光器。作为初步结果，氧化膜条形器件阈值电流为200－700mA，单模输出功率至少为20mW，单模工作持续到至少80℃。 在以上工作的基础上，本论文在国际上首次提出了一种采用吸收光栅的新型增益耦合型DFB激光器／电吸收型调制器单片集成光源的器件结构。由于该结构中激光器和调制器部分采用了完全相同的量子阶有源层，从而能够在一次外延中同时形成激光器和调制器，使制作工艺得到简化。本论文通过理论计算分析了该器件的原理可行性，并同实验结果进行了比较。最后，采用MBE方法在国际上首次进行了GaAIAs／GaAs多量子阱增益耦合型DFB激光器／电吸收型调制器单片集成光源的制作尝试，并取得了初步结果。器件阈值为130mA，调制器部分在4－6.5V反向偏压下观察到了调制现象。
Multiple quantum well (MQW) gain-coupled (GC) distributed-feedback (DFB)laser/electroabsorption (EA) modulator monolithically integrated light source as akind of photonic integrated circuits (PIC) is investigated theoretically andexperimentally in this dissertation. First, characteristics including single-mode selectivity, modulation-inducedwavelength shift (chirping), and fight output efficiency of the integrated light sourceswith GC-, quarter-wave-shifted (QWS) and conventional index-coupled (IC) DFBlaser sections are calculated and compared. The chirping of GC-PIC is nearly thesame as that of IC-PIC and QWS-PIC, but the single-mode selectivity of GC-PIC ismuch better than that of IC-PIC and QWS-PIC. Furthermore, when HR-AR coatingis introduced, which is favorite for high power operation, GC-PIC shows much higherprobability of single-mode operation than IC-PIC, while QWS-PIC can not work inthis case. Without the need for phase shifted gratings, the processing of GC-PIC ismuch simpler than that of QWS-PIC. Therefore GC-DFB laser/EA modulatorintegrated fight source is very promising for optical communication. Second, the absorption coefficient of MQW structure when applying electricalfield is calculated. A novel approach of optimization of MQW EA modulator isproposed, and the structure of GaAlAs/GaAs MQW waveguide modulator isoptimized as an example. The EA property of GaAlAs/GaAs MQW structure isstudied experimentally. An InGaAs/InMAs MQW EA modulator suitable for opticalcommunication is Fabricated for the first time in our country which achieved an on-offratio of 7 dB under 2 V driving voltage. Third, GaAlAs/GaAs MQW GC-DFB laser is designed, in which the duty cycleand t hickness of the absorptive grating layer is optimized. As a preparationexperiment, a GaA]As/GaAs MQW separate confinement heterostructure (SCH) laseris fabricated, and threshold current density of 2000 A/cm2 is obtained. A noveltechnique of molecular beam epitaxy (MBE) regrowth on corrugated surface isdeveloped based on the nature of selective thermal etching of GaAIA-s/GaAs materials.In the processing, not only the shape of grating can be precisely controlled but also aclean interface can be obtained. With this technique, an all-MBE grownGaAlAs/GaAs MQW GC-DFB laser with absorptive gratings is fabricated for the firsttime. As a primary result, threshold current of 200-700 mA and DFB modeoscillation within a range of at least 80'C is achieved, and stable single longitudinalmode oscillation is maintained up to at least 20 mW output. On the basis of the above work, a novel structure of light source of GaAlAs/GaAsMQW GC-DFB laser with absorptive gratings integrated with EA modulator isproposed for the first time. In the structure, both laser and modulator sections adoptthe same MQW active layer, hence they can be formed in a single-step epitaxy, whichsimplifies the fabrication process. Device operation mechanism is analyzedtheoretically, and the results are compared with experiments. Finally, GaM"GaAsMQW GC-DFB laser/EA modulator integrated light source is fabricated all by MBEfor the first time. As a primary result, threshold current of 130 mA is obtained andmodulation phenomenon is observed under bias of 4 to 6.5 V.
