Fig. 1. Schematic of the FDL laser frequency stabilization. AOM, acousto-optic modulator; Iso, optical isolator; PD, photodetector; FDL, fiber delay line; FM, Faraday mirror; RF, radio frequency; HMI signal, heterodyne Michelson interferometer signal.

Fig. 2. Schematic of the vacuum chamber.

Fig. 3. Temperature distribution nephogram and fluctuations of components inside the vacuum chamber. (a) Temperature nephogram of the five-layer thermal shield, AOM, and fiber spool; (b-1) temperature fluctuation of the first-layer shield; (b-2) simulated temperature fluctuation on the optical fiber; (c-1) temperature fluctuation of the vacuum chamber; (c-2) simulated temperature fluctuation on the optical power and RF power circuits.

Fig. 4. Free-running relative power fluctuation to (a) the optical power injected into the interferometer and (b) the RF power driving the AOM2. FDL-stabilized laser frequency step response to (c) the optical power injected into the interferometer and (d) the RF power driving the AOM2.

Fig. 5. FFT spectrum of the beat-note signal (blue circles) and its Gaussian fit (red line).

Fig. 6. Frequency noise PSD of the FDL-stabilized laser.

Fig. 7. Fractional frequency instability of the FDL-stabilized laser. The inset displays the FDL-stabilized laser frequency fluctuation to the current work (red line) and our previous work (blue line)^[17].