Modulation-free laser frequency stabilization via balanced detection of common-path Fano resonance in all-PM fiber cavity

Le résumé fourni par la source

Laser frequency stabilization is indispensable for extensive applications involving precision measurements, and the best performance has been achieved with the Pound–Drever–Hall technique. However, it relies on a bulky ultrastable Fabry–Pérot cavity with demanding environment disturbance isolation techniques, along with electro-optical modulation. Here, we present a modulation-free approach for laser frequency locking to an all-polarization-maintaining (PM) fiber cavity, and the error signal is obtained from balanced detection of common-path Fano resonance. The asymmetric Fano resonance arises from the common-path interference of the two intrinsic polarization modes in the all-PM fiber cavity, and balanced detection is used to eliminate the non-zero bias of the Fano resonance. Moreover, we also adopt birefringence compensation to alleviate the influence of temperature fluctuations on the phase bias, which is crucial for a highly stable Fano resonance. After locking to the zero-biased stable Fano resonance, we achieve a laser frequency drift less than 1 MHz within 400 s, and the laser frequency noise is lowered to 3 × 103 Hz2/Hz at 1 kHz and 1 × 104 Hz2/Hz at 200 Hz. We believe that this is a versatile, compact, and simple laser frequency stabilization approach and can thus be widely used in diverse scenarios for laser interferometry and precision measurements.

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