Development of DFB Lasers with New Structures for Complete Single-Longitudinal-Mode Oscillation

作为研制具有调制条纹宽度结构的0.8微米距离分布反馈(DFB)激光器的第一步，本课题组于1985学年研制了GaAlAs/GaAs脊波导DFB激光器，获得了当时最低的阈值电流和较高的微分量子效率。由此证明了在短波长范围内获得可行的DFB激光器的可能性，但从精确的侧模分析发现，这种波导结构并不一定有利于液相外延(LPE)。1986学年首次将双沟道平面掩埋异质结用于制作GaAlAs/GaAsDFB激光器，作为一种更适合于LPE的波导结构。所得到的器件在特性上获得了显著的改善，例如阈值电流为12 mA，是迄今报道的最低的。然后，将各种条带宽度调制方案应用于显影…更多的ED器件，其中实际上完成了完整的单纵模(SLM)振荡，这与理论预测一致。研究人员神宫研究了半导体激光器的材料物理，朝着其功能的另一种演变。他利用相移法测定了半导体中的载流子寿命和复合系数。讨论了俄歇复合对半导体激光器双稳特性温度依赖性的影响。这些研究有助于获得描述半导体激光器的详细速率方程，并获得更高的材料参数精度。研究人员Nagai通过两个面解理结构研究了DFB激光器的SLM操作。他从理论和实验上讨论了具有解理小面的1.3和1.5微米器件中的SLM概率和工作温度范围，从而有助于阐明解理小面结构的有效性。研究人员秋叶利用四分之一波移位结构研究了SLM振荡。通过对1.5微米量程四分之一波长移相器的详细理论研究和实验观察，确立了设计原则和制作工艺，从而为此类激光器的实际应用做出了贡献。较少

As a primary step to develop 0.8 <mu> m range distributed feedback (DFB) lasers with modulated stripe width structure, the head investigator and coworkers fabricated and studied GaAlAs/GaAs ridge waveguide DFB lasers in 1985 academic year and achieved the lowest threshold current and high differential quantum efficiency at that time. Possibility of obtaining feasible DFB lasers in the short wavelength regime was thereby shown, yet it was found from a precise lateral mode analysis that this waveguide structure is not necessarily favorable to liquid phase epitaxy (LPE). In 1986 academic year, double channel planar buried heterostructure was instead employed in fabricating GaAlAs/GaAs DFB lasers for the first time, as a more appropriate waveguide structure for LPE. Significant improvements in characteristics were attained in the resulting devices, such as threshold current of 12mA which was the lowerst ever reported. Various stripe width modulation schemes were then applied to the develop … More ed devices, where complete single-longitudinal= mode (SLM) oscillation was in practice accomplished, being consistent with theoretical predictions.Investigator Kamiya studied material physics of semiconductor lasers toward another evolution of their functions. He determined carrier lifetime and recombination coefficients in semiconductors making use of a phase shift method. The effects of Auger recombination on temperature dependence of bistable characteristics in semiconducor lasers were also discussed. These studies contributed to obtaining detailed rate equations describing semiconductor lasers, and acquiring increased accuracy in material parameters.Investigator Nagai examined SLM operation of DFB lasers by means of both facets cleaved structure. He discussed theoretically and experimentally SLM probability and temperature range of SLM operation in 1.3 and 1.5 <mu> m devices with cleaved facets, thus contributing to clarification of the effectiveness of the cleaved facet structure.Investigator Akiba studied SLM oscillation by quarter-wave-shifted structure. Through detailed theoretical examination and experimental observation of 1.5 <mu> m range quarter-wave-shifted devices, he established design principles and fabrication techniques, thereby contributed toward practical applications of such lasers. Less