All-fiber passively mode-locked laser oscillator at 1.5 μm with watts-level average output power and high repetition rate

We report on a passively mode-locked all-fiber laser oscillator at 1.5 μm based on heavily doped phosphateglass active fiber. An active fiber only 20 cm long is sufficient to produce as much as 2.4 W of average output power directly from the oscillator. The width of the mode-locked pulses varies from 8 ps at the lowest output power in the mode-locked state to 44 ps at the highest power. Our picosecond laser oscillator features a high repetition rate of 95 MHz and high peak pulse power of ~540 W. The oscillator combines the convenience of all-fiber construction with power performance that was previously achievable only with mode-locked bulkoptic laser oscillators or more complex systems involving fiber amplifiers.