Characteristics of intensity noise of optically pumped vertical-cavity surface-emitting lasers and solid-state lasers, induced by the beating of the main lasing mode and non-lasing side modes and its reduction, have been reported in recent years. The mode beating noise of an external cavity diode laser composed of an electrically pumped edge-emitting laser diode chip is studied experimentally in this Letter. The noises due to the beating of the main mode with the first- to third-order side modes are observed, and multiple sub-peaks in the beating noise are measured. It is assumed that the new phenomena are coming from the enhanced four-wave mixing in the longer-active medium. Intensity noise reduction is also demonstrated by using the second harmonic generation of a beta barium borate crystal as a nonlinear absorber.

中文翻译：

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外腔二极管激光器高频范围内的强度噪声及其二次谐波的降低

近年来，已经报道了由主激射模和非激射侧模的跳动及其降低引起的光泵浦垂直腔面发射激光器和固态激光器的强度噪声的特性。在这封信中，通过实验研究了由电泵浦边缘发射激光二极管芯片组成的外腔二极管激光器的模式拍噪声。观察到由于主模式被一阶至三阶副模式的跳动而产生的噪声，并测量了该跳动噪声中的多个子峰。假定新现象是由于在长效介质中增强的四波混频引起的。通过使用β硼酸钡晶体的二次谐波作为非线性吸收体，也可以证明强度降低。