GHz fundamental mode-locking of a highly integrated Er-doped all-fiber ring laser
Maolin Dai, Bowen Liu, Yifan Ma, Ruoao Yang, Zhigang Zhang, Sze Yun Set, Shinji Yamashita
Abstract
High repetition rate ultrafast fiber lasers are essential for both scientific research and industrial applications. Here, we report the first, to the best of our knowledge, all-fiber ring laser with a fundamental repetition rate exceeding 1 GHz, by integrating all necessary functions into one single device with commercial active fiber pigtails. Low-threshold self-starting mode-locking is achieved by using a carbon nanotube (CNT) saturable absorber that directly deposits on the Er-doped fiber connector. The laser operates at 1562 nm, delivering 682 fs pulses with 1.028 GHz fundamental repetition rate with good stability, low intensity/phase noise, and high signal-to-noise ratio. The proposed compact source is promising for high repetition rate applications and provides a reference for fiber lasers with different mode-locking mechanisms or in various wavelength ranges. We also provide in-depth discussions on the key challenges and future directions for fiber lasers mode-locking at GHz rates using real saturable absorbers.