Fig. 1. Experimental setup of the laser stabilization system. PZT: piezoelectric transducer; AOM: acousto-optic modulator; VCO: voltage-controlled oscillator; RF: radio frequency.

Fig. 2. Schematic of the vacuum chamber.

Fig. 3. Normalized FFT spectrum of the beat-note signal (blue circles) and its Gaussian fit (red line).

Fig. 4. Frequency noise PSD of (a) two identical FDL-stabilized lasers (black solid line), (b) thermomechanical noise from the optical fiber (red dash line), and (c) thermal noise of the first-stage amplifier after the photodiode (blue solid line).

Fig. 5. Fractional frequency instability of FDL-stabilized lasers. The dashed curve denotes the thermomechanical noise limit of the optical fiber.