基于FPGA控制扫描腔的长期激光频率稳定
Long-term laser frequency stabilization with an FPGA-controlled scanning cavity
AI总结：
提出基于FPGA的扫描转移腔锁定方案，通过连续扫描法布里-珀罗腔同时稳定多个激光器，利用低延迟实现快速扫描，达到亚MHz长期稳定，并验证于镱原子磁光阱实验。
摘要：
我们提出了一种基于FPGA的扫描转移腔锁定（STCL）实现方案，用于激光频率稳定，该方案通过连续扫描的法布里-珀罗腔，能够同时将多个激光源稳定到单个参考激光器上。通过利用FPGA架构同时执行腔扫描、峰值检测和反馈驱动，我们最小化了延迟，并允许在单个设备内为多个激光器提供独立的控制回路，实现了直接的可扩展性。系统性能通过从短时间（<1秒）到长时间（~20小时）的外差测量进行分析。通过磁光阱中镱原子的原子光谱验证了端到端锁定性能，展示了在可见光波长范围内跨~150 nm的稳定性转移中，数小时内亚MHz的绝对频率稳定。重要的是，我们展示了一种基于声光调制器（AOM）频率调制的新型快速扫描方法，这得益于我们FPGA实现的低检测延迟。与标准的压电驱动腔长扫描相比，这显著提高了有效锁定带宽并降低了系统的固有噪声，实现了亚100 kHz的长期稳定性，并为激光线宽压缩提供了前景。由于其模块化、低成本以及易于在STEMlab Red Pitaya平台的开源PyRPL固件包中实现，我们的架构为现有的STCL和锁定腔实现提供了一种紧凑且灵活的替代方案，为无需依赖任何原子参考进行激光稳定的先进冷原子实验操作提供了一种实用方法。
英文摘要：
We present an FPGA-based implementation of a scanning transfer cavity lock (STCL) for laser frequency stabilization, allowing for the simultaneous stabilization of multiple laser sources with respect to a single reference laser by means of a continuously scanned Fabry-Perot cavity. By exploiting the FPGA architecture to simultaneously perform cavity scanning, peak detection, and feedback actuation, we minimize latency and allow independent control loops for several lasers within a single device, offering direct scalability. The system performance is analyzed through heterodyne measurements from short ($<1\,$s) to long ($\sim20\,$hours) timescales. The end-to-end locking performance is validated through atomic spectroscopy of ytterbium atoms in a magneto-optical trap, demonstrating sub-MHz absolute frequency stability over several hours for the stability transfer across $\sim 150\,$nm in the visible-wavelength range. Importantly, we demonstrate a novel fast-scanning approach based on acousto-optic modulator (AOM) frequency modulation, enabled by the low detection latency of our FPGA implementation. This increases significantly the effective locking bandwidth and reduces the intrinsic noise of the system with respect to standard piezo-actuated scanning of the cavity length, allowing to reach sub-$100\,$kHz long-term stability and offering perspectives for laser-line narrowing. Owing to its modularity, low cost and ease of implementation within the open-source PyRPL firmware package for the STEMlab Red Pitaya platform, our architecture offers a compact and flexible alternative to existing STCL and locked-cavity implementations, providing a practical approach to the operation of a state-of-the-art cold-atom experiment without relying on any atomic references for laser stabilization.
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