A theoretical analysis of the behavior of the frequency/phase noise of semiconductor lasers with external phase conjugate feedback is presented. It is shown that the frequency noise is drastically reduced even for lasers with butt-coupled phase conjugate mirrors. In this laser system, the phase noise takes a finite-low value corresponding to a state of first-order self-phase locking of the laser. As a result, the spectral shape of the laser signal does not remain Lorentzian but collapses around the carrier to a delta function with a close to carrier noise level of less than -137 dBc/Hz. The total phase variance of this laser signal, in a 20 GHz noise bandwidth, is less than 0.002 rad^2
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机译：提出了具有外部相位共轭反馈的半导体激光器的频率/相位噪声行为的理论分析。结果表明，即使对于具有对接耦合共轭镜的激光器，频率噪声也被大大降低。在该激光器系统中，相位噪声取与激光器的一阶自相位锁定状态相对应的有限低值。结果，激光信号的光谱形状不会保持洛伦兹（Lorentzian）形，而是会在载波周围塌陷为三角函数，接近载波噪声水平小于-137 dBc / Hz。在20 GHz噪声带宽下，此激光信号的总相位方差小于0.002 rad ^ 2
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