Active Cancellation of Servo-Induced Noise on Stabilized Lasers via Feedforward
Active Cancellation of Servo-Induced Noise on Stabilized Lasers via Feedforward
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DOI：
10.1103/physrevapplied.18.064005
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发表时间：
2022-08
影响因子：
4.6
通讯作者：
Lintao Li;W. Huie;Neville Chen;B. Demarco;J. Covey
中科院分区：
文献类型：
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作者：
Lintao Li;W. Huie;Neville Chen;B. Demarco;J. Covey
许多精密激光应用需要主动稳频。然而，这种稳定回路通过将噪声推到其带宽之外的频率来工作，从而导致巨大的“伺服颠簸”，这可能对某些应用产生有害影响。过滤这种噪声的主要方法是让激光通过高精细度的光腔，这对系统设计造成了限制。在这里，我们提出并演示了一种不同的方法，其中频率误差信号来自激光和通过参考腔的光之间的拍音。从这个拍音产生的相位噪声在激光后被前馈到电光调制器，仔细考虑相对延迟，进行实时频率校正。使用hz线宽激光器，我们在伺服凸起的峰值处显示了$ $ gtrsim20$ dB的噪声抑制（$ $约250$ kHz），并且噪声抑制带宽为$ $ $ 5$ MHz，远远超出了伺服凸起。通过用我们的测量数据模拟两能级原子的拉比动力学，我们证明了在广泛的拉比频率范围内脉冲保真度的实质性改进。我们的方法提供了一种简单而通用的方法来获得窄线宽激光器的干净光谱，这是许多新兴冷原子应用所需要的，并且很容易与商业系统兼容，甚至可能包括波长转换。
Many precision laser applications require active frequency stabilization. However, such stabilization loops operate by pushing noise to frequencies outside their bandwidth, leading to large"servo bumps"that can have deleterious effects for certain applications. The prevailing approach to filtering this noise is to pass the laser through a high finesse optical cavity, which places constraints on the system design. Here, we propose and demonstrate a different approach where a frequency error signal is derived from a beat note between the laser and the light that passes through the reference cavity. The phase noise derived from this beat note is fed forward to an electro-optic modulator after the laser, carefully accounting for relative delay, for real-time frequency correction. With a Hz-linewidth laser, we show $\gtrsim20$ dB noise suppression at the peak of the servo bump ($\approx250$ kHz), and a noise suppression bandwidth of $\approx5$ MHz -- well beyond the servo bump. By simulating the Rabi dynamics of a two-level atom with our measured data, we demonstrate substantial improvements to the pulse fidelity over a wide range of Rabi frequencies. Our approach offers a simple and versatile method for obtaining a clean spectrum of a narrow linewidth laser, as required in many emerging applications of cold atoms, and is readily compatible with commercial systems that may even include wavelength conversion.