783-MHz fundamental repetition rate, Er-doped all-fiber ring laser mode-locked by carbon nanotubes

We have demonstrated 783-MHz fundamental repetition rate from a compact and robust Er-doped all-fiber ring laser mode-locked by carbon nanotubes (CNT), with pulse width of 623 fs at center wavelength of 1562 nm. To the best of our knowledge, this is the highest fundamental repetition rate has been reported from an all-fiber ring laser. By using CNT saturable absorber (SA), a relatively low self-starting pump threshold of 108 mW is achieved. The laser has a very compact footprint less than 10 cm X 10 cm, benefiting from the all-active-fiber cavity design. The robust mode-locking is confirmed by the low relative intensity noise (RIN) and a long-term stability test. We propose a new scheme for generating high repetition rate femtosecond optical pulses from a compact and stable all-fiber ring laser.