Pound–Drever–Hall (PDH) laser frequency stabilization is a powerful technique widely used for building narrow linewidth lasers. This technique is, however, ineffective in suppressing high-frequency (>100kHz) laser phase noise detrimental for many applications. Here, we introduce an effective method that can greatly enhance its high-frequency performance. The idea is to recycle the residual PDH signal of a laser locked to a cavity by feedforwarding it directly to the laser output field after a delay fiber. Using this straightforward method, we demonstrate a phase noise suppression capability about four orders of magnitude better than just using the usual PDH feedback for noise around a few MHz. We further find that this method exhibits noise suppression performance equivalent to cavity filtering. This method holds great promise for applications demanding highly stable lasers with diminished phase noise up to tens of MHz (e.g., precise and high-speed control of atomic and molecular quantum states).

中文翻译：

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Pound–Drever–Hall 前馈：反馈之外的激光相位噪声抑制


庞德-德雷弗-霍尔 (PDH) 激光稳频是一种广泛用于构建窄线宽激光器的强大技术。然而，该技术无法有效抑制对许多应用有害的高频（>100kHz）激光相位噪声。在这里，我们介绍一种有效的方法，可以大大增强其高频性能。这个想法是通过将锁定到腔体的激光器的残余 PDH 信号直接前馈到延迟光纤之后的激光输出场来回收该信号。使用这种简单的方法，我们展示了相位噪声抑制能力，比仅使用常见的 PDH 反馈抑制几 MHz 左右的噪声要好约四个数量级。我们进一步发现该方法表现出与空腔滤波相当的噪声抑制性能。这种方法对于需要高度稳定的激光器（相位噪声降低高达数十 MHz）的应用具有巨大的前景（例如，原子和分子量子态的精确和高速控制）。