The Pound–Drever–Hall (PDH) cavity-locking scheme has found prevalent uses in precision optical interferometry and laser frequency stabilization. A form of frequency modulation spectroscopy, PDH enjoys superior signal-to-noise recovery, large acquisition dynamic range, wide servo bandwidth, and robust rejection of spurious effects. However, residual amplitude modulation at the signal frequency, while significantly suppressed, still presents an important concern for further advancing the state-of-the-art performances. Here we present a simplified and improved scheme for PDH using an acousto-optic modulator to generate digital phase reference sidebands instead of the traditionally used electro-optic modulator approach. We demonstrate four key advantages: (1) the carrier and two modulation tones are individually synthesized and easily reconfigured, (2) robust and orthogonal control of the modulated optical field is applied directly to the amplitude and phase quadratures, (3) modulation synthesis, demodulation, and feedback are implemented in a self-contained and easily reproducible electronic unit, and (4) superior active and passive control of residual amplitude modulation is achieved, especially when the carrier power is vanishingly low. These distinct merits stimulate new ideas on how we optimally enact PDH for a wide range of applications.

中文翻译：

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用于无 AM 精密激光稳定和光谱的合成 FM 三重态

Pound-Drever-Hall (PDH) 腔锁定方案在精密光学干涉测量和激光频率稳定方面得到了广泛应用。PDH 是调频光谱的一种形式，具有卓越的信噪比恢复、大采集动态范围、宽伺服带宽和强大的寄生效应抑制能力。然而，信号频率处的残余幅度调制虽然被显着抑制，但仍然是进一步提高最先进性能的重要问题。在这里，我们提出了一种简化和改进的 PDH 方案，使用声光调制器来生成数字相位参考边带，而不是传统使用的电光调制器方法。我们展示了四个关键优势：(1) 载波和两个调制音调单独合成并易于重新配置，(2) 调制光场的稳健和正交控制直接应用于幅度和相位正交，(3) 调制合成，解调和反馈在独立且易于复制的电子单元中实现，并且（4）实现了剩余幅度调制的优异主动和被动控制，特别是当载波功率极低时。这些独特的优点激发了我们如何为广泛的应用优化制定 PDH 的新想法。