Long-term frequency-stabilized Er:fiber-based optical frequency comb with nonlinear amplifying loop mirror

The optical frequency comb (OFC) technology can synchronize the phase of the microwave and optical frequency, which solves the problem of optical frequency measurement in the past, and can achieve precise measurement of a wide range of frequencies. In this paper, we describe an Er:fiber OFC based on a NALM laser that can self-start mode locking. The spectrum of the comb reaches 60 nm, and the repetition frequency is 200 MHz. Moreover, the carrier envelope offset frequency (f_ceo), with a signal-to-noise ratio (SNR) of 38 dB in 300 kHz resolution bandwidth (RBW), is detected by a common path ƒ-2ƒ interferometer. We achieved the optical comb lock to the ultra-stable laser by controlling the piezoelectric ceramic transducer (PZT) and electronic optical modulator (EOM) in the laser cavity. The fceo is locked by controlling the pump current source. The frequency stability of f_beat and f_ceo are 8.5×10^-18/τ^1/2 and 7.5×10^-18/τ^1/2 , respectively, and the phase noise are 0.14 rad and 0.99 rad from of 1 Hz to 1 MHz, respectively. We believe the present all polarization-maintaining (PM) fiber frequency comb combines a robust system architecture with ultra-low noise performance and will be very attractive for even the most demanding comb applications.