Long-term repetition-frequency stabilization of all-normal-dispersion Yb-doped fiber laser to the cesium standard

Abstract

Repetition-frequency stabilization of a Yb-doped fiber laser to the Cesium standard is reported. Laser amplitude and phase noise is characterized. Performance is limited to 2x10 -14 at 100000 averaging time by intrinsic stability of the Cs-standard. ©2010 Optical Society of America Femtosecond laser frequency comb has revolutionized frequency metrology in recent years. While most of the initial activity utilized Ti:sapphire lasers, frequency combs generated from fiber lasers are increasingly important due to their advantages in long-term stability, cost-efficiency and operation-convenience [1]. Extremely long durations of uninterrupted operation are being reported from mode-locked fiber lasers. However, most of the activity is centered on Er-doped fiber lasers, with very few reports [2] utilizing Yb-doped fiber lasers, even though this gain medium offers superior technical performance in nearly every aspect. In particular, all-normal-dispersion (ANDi) lasers have been attracting much attention with their simplified cavity, increased ease-of-mode-locking and good technical performance [3]. However, to date, there is no study exploring the long-term stability of an ANDi laser, nor its use for comb generation. Here, we demonstrate for the first time to our knowledge, long-term (over several days) stabilization of an ANDi Yb-doped fiber laser to a Cs frequency standard. Characterization of short-term amplitude and phase noise characterization of the oscillator coupled with its long-term stability demonstrates its potential for use as a frequency-comb generator.The Yb-doped fiber laser has been constructed with a focus on its long-term stability and ease of transportation ( Fig. 1(a)). The laser includes both a fast, piezo-based fiber stretcher and a slow, motorized translation stage to control the cavity length. The motorized stage is used to roughly set the repetition rate to the desired value and the fast stretcher is used for electronic locking to the reference. The repetition rate is 108.33 MHz (12 nd sub-harmonic of 1.3 GHz), and the laser produces 0.8 nJ-energy chirped pulses, which can be dechirped to 127 fs. The optical spectrum is characteristic of this laser type (inset of Fig.