A 51-dB signal-to-noise ratio carrier-envelope offset frequency in an environmentally stabilized polarization-maintaining optical frequency comb

A femtosecond optical frequency comb (OFC) based on a laser with a nonlinear amplification loop mirror mode-locking mechanism is proposed. The laser adopts a fully polarization-maintaining (PM) structure, which can realize self-starting mode-locking at the center wavelength of 1560.2 nm with a 195.65 MHz repetition rate at a pump power of 630 mW, and the frequency stability after phase-locking is 1.95 × 10⁻¹² with a 1-s averaging time. Through a homemade f–2f interferometer, the detected free-running f_ceo signal exhibits a signal-to-noise ratio (SNR) as high as 51 dB. After phase-locking, f_ceo has a frequency stability of 1.17 × 10⁻¹¹ with a 1-s averaging time.