【作者】 邱运涛；

【导师】 王智勇；

【作者基本信息】 北京工业大学 ， 光学工程， 2008， 硕士

【摘要】 半导体激光阵列(一维半导体激光阵列bar和半导体激光叠层阵列stack)是实现大功率输出的有效技术途径,由于其高功率、高效率、体积小、寿命长等优点,目前已广泛应用于材料加工、通讯、医疗、泵浦固体激光器及军事等诸多领域。但是,由于其空间相干性不好,使它的光束质量很差,限制了其在许多领域直接应用,因此改善半导体激光器的光束质量是扩展半导体激光器应用领域的一项必要工作。目前的外腔锁相技术主要都是直接在半导体激光器外部加入一些反馈装置以实现锁相的,这些方法都存在着锁相同时不能保证光束空间对称性以及实际运行中如何对基超模进行选择等问题。光纤相干耦合技术就是先通过光纤阵列将半导体激光阵列的光束进行整型后再在光纤阵列的输出端形成新的外腔,实现锁相的同时整个系统输出的光束也具有较高的空间对称性,进而提高了锁相时的超模质量,更有利于实际应用的需要。由于光纤相干耦合在实际操作中对外腔腔长、腔型等参数比较敏感,因此需要一个完整的理论模型对其进行锁相行为描述。本文利用耦合模理论建立了光纤相干耦合半导体激光器的超模理论模型,推导了该锁相方式下的耦合系数矩阵和超模的近远场分布。发现该锁相方式的更有利于基超模的运转,提高激光器的光束质量。通过对系统的耦合系数的分析,并利用遗传算法对不同的腔型进行优化处理,得到了几种典型腔型的优化结果。通过对各个结果的稳定性的分析得到了适合锁相的外腔腔型。利用光纤相干耦合的方法在实验中以平面镜加凸透镜组成的外腔实现了对半导体激光阵列的锁相,在工作电流略高于阈值电流的条件下得到了线宽小于0.3nm的激光输出。更多还原

【Abstract】 Laser Diode Array (LDA), including linear laser diode array and laser diode stack, is an attractive technique to realize higher output power. It has applied to many fields such as material processing, communication, medical, diode pumped solid laser and military because of its high power, high efficiency, small size and long lifetime. However, as a result of its low spatial coherence, LDA suffers from a poor beam quality which limits the direct application in many fields. Therefore, to improve the beam quality of LDA is an essential work to extend the field of its application. The existing phase-locking means are some feedback devices which direct role in LDA while they can not improve the spatial symmetry of LDA efficiently. They also have the problem how to select the fundamental super mode.Fiber coherent coupling is a novel phase-locking means which can improve the spatial symmetry because of the beam shaping of fiber array. This thesis founds the theory model of LDA coherently coupled by fiber array, and deduces coupling coefficients matrix and the near/far field distribution of LDA. The phase-locking mean is easier to work in fundamental super mode than other means. A theory model needs to be founded, for the reason that phase locking of fiber coherent coupling is sensitive of the parameters of its cavity. This thesis founded the super mode theory model of fiber coherent coupling LDA by coupled mode theory. The coupling coefficient matrix and near/far field intensity distribution was deduced. Furthermore, we found that the fundamental mode is easier to selected than higher modes. We analyzed the coupling coefficient of the LDA phase-locked by fiber array and found the best result of the parameters of some classical cavities by genetic algorithm. Then we analyzed the stability of different result and got the cavity which is most suitable for phase-locking.Finally, we achieve the phase-lock of LDA coherently coupled by fiber array in the condition that the work current is little higher then threshold current, while the FWHM of the spectrum has narrowed to 0.3nm.更多还原