2025/12/03 by Hildebrand, Roame A., Wang, Wance, Goham, Connor +2
Engineering · Physics and Astronomy · #Advanced Fiber Laser Technologies #Advanced Frequency and Time Standards #Advanced Measurement and Metrology Techniques #Atomic Physics (physics.atom-ph) #FOS: Physical sciences #Optics (physics.optics)
paper · doi:10.48550/arxiv.2512.03900
openalex publication_date 2025/12/03 · openalex created_date 2025/12/05 · openalex updated_date 2026/07/28
The Pound-Drever-Hall (PDH) technique is widely used to stabilize the frequency of lasers. Here we report on a routinely underestimated source of error in PDH offset-locking: a shift in the lock point due to the unintended interaction between residual optical sidebands and higher-order spatial modes in misaligned Fabry-Perot cavities. Significant frequency deviations-up to 50% of the cavity linewidth-can arise when the optical offset is obtained from a sinusoidally driven EOM. We measure this deviation experimentally, find agreement with a simple model, and show how a spectrally-pure frequency offset can reduce the deviation by an order of magnitude. Our findings draw attention to a systematic effect of importance to precision optical spectroscopy, optical clocks, and quantum information science.