We use a Michelson interferometer to explore the spectroscopic properties of laser diode emission over a wide range of operational conditions. By studying how the interferogram changes with drive current, we demonstrate the relationship between coherence length and spectral bandwidth. At low injection current, the laser source operates more like an ordinary light-emitting diode (LED), generating a relatively broad spectrum with short coherence length. In contrast, when the drive current exceeds the single-mode lasing threshold, we obtain a steady sinusoidal interferogram throughout the movable mirror scanning range, indicative of monochromatic light. At intermediate injection, we observe a beating pattern due to the presence of multiple longitudinal lasing modes. We verify that the beat distance, or optical travel between beats, is consistent with the spectrally validated mode spacing.

中文翻译：

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激光二极管相干性

我们使用迈克尔逊干涉仪来探索激光二极管在各种操作条件下发射的光谱特性。通过研究干涉图如何随驱动电流变化，我们证明了相干长度和光谱带宽之间的关系。在低注入电流下，激光源的工作方式更像普通的发光二极管 (LED)，产生的光谱相对较宽，相干长度较短。相比之下，当驱动电流超过单模激光阈值时，我们在整个可移动反射镜扫描范围内获得稳定的正弦干涉图，表示单色光。在中间注入时，由于存在多个纵向激光​​模式，我们观察到跳动模式。我们验证节拍距离或节拍之间的光学旅行，