【作者】 陈海波；

【导师】 陈建国；

【作者基本信息】 四川大学 ， 光学， 2005， 硕士

【摘要】 半导体激光器列阵(LDA)结构紧凑,体积小,效率高,已被广泛应用于空间光通信,泵浦固体激光器,材料加工等众多领域。但是目前商用大功率LDA发光单元间距较大(～500μm),因而各单元之间不存在实质性的内在耦合,即单元的电场之间缺乏相干性,这就导致了LDA输出的光束质量较差,限制了LDA在其它领域的应用。为了克服这一缺点,LDA单元间的位相锁定成为了近几年的研究热点。 外腔锁相因其结构简单、效果明显,因而在外部耦合锁相方法中倍受关注。已经有不少理论对LDA外腔锁相进行分析,也有不少试验结果证明了这些理论的合理性,但这些理论大部是在考虑具体的外腔参数的情况下对锁相LDA进行的分析,不具有普适性。本文在不针对特定的外腔参数的情况下并考虑到外腔锁相LDA的阈值与前端面的剩余反射系数有关这一事实,对外腔锁相LDA进行了一般性的分析。在只计相邻发光单元间互相耦合及单元自耦合的近似下,解析证明出外腔锁相LDA阈值最低的模要么是基超模要么是高阶超模,说明了存在一些分立的外腔长度范围可以使LDA运行于基超模或最高阶超模。 实现LDA外腔锁相一个关键因素就是每个发光单元的光场频率不能相差太大,这就要求LDA热沉散热效率要很高,因为不均匀的散热会导致单元纵模频率的变化。本文通过解热传导方程得到了半导体激光器列阵的热沉温升分布的解析表达式,并利用该解析式分析了热传导系数对热沉散热的影响,与有限元法相比,本方法物理模型清晰、计算量明显减少,并可对参数进行直观的分析,为安装冷却器提供了一种较为简单和方便的参考依据,也为有限元法提更多还原

【Abstract】 Laser diode array (LDA) is characterized by its compactness and high efficiency. It has been widely used in free-space optical communications, solid lasers pumping, and material processing. But LDA generally operates in multiple lateral modes, and the outputs of its individual emitters are incoherent because of it’s broad stripe emitters, which worsen the output quality of LDA, and therefore LDA’s application in other fields has been limited. The phase locking of LDA is a potential method to overcome the shortcoming, and it has become a hot topic in recent years.There have been many theories analyzing the mechanism of phase-locking of LDA by external cavity (EC), and the suitability of these theories has also been confirmed by experiments. But those theories are usually based on EC with specific parameters, and hence they cannot be generally used to analyze the phase locking mechanism in the universal sense. In this thesis, we have made a general discussion on LDAs of broad tripe emitters phase locked with ECs without referring to specific device parameters. For a phase locked LDA based on the diffraction coupling between the nearest neighbor emitters, analytical solutions have been derived for the coupling matrix equation, including the finite reflection of the front facet of the LDA facing the EC. Even though the thresholds of the super modes of anLDA are affected by the residual reflection at the front facet, it can still be proved analytically that the favored mode of the LDA is either the lowest or highest order super mode.A key factor, to some extent, determines the phase-locking of LDA is that the conformidity of the frequencies of the individual emitters. If the frequency differences becomes too large, it is difficult to phase lock the LDA. So the efficiency of heat sink is very important to phase-locking. A heat sink of low efficiency of will lead to large frequency excursions among emitters. In this work, the analytical expression of the temperature rise of the heat sink of an LDA has been obtained by solving the heat conduction equation. The influence of convection heat transfer coefficient on the temperature rise of the sink top and the bottom surface has been analyzed. The results obtained are in agree with that calculated with the finite element method and confirmed by the experiment results.In this work, phase-locking of an LDA has been achieved by using a simple EC consisting of a fast axis collimating lens and a high-reflection external mirror. The quality of the output beam has been improved. The far field pattern consists of 3 lobes, and the divergence of each lobe is about 10 mrad. The spectrum has been narrowed from 2.2nm to 0.3nm and the threshold current decreases from 7.0A to 5.5A with and without feedback respectively.更多还原