Tunable thulium-doped mode-locked fiber laser with watt-level average power.

We demonstrate a wavelength-tunable, sub-200 fs, and watt-level thulium-doped ultrafast fiber oscillator with a fundamental frequency repetition rate of 509.7 MHz. The wavelength can be tuned between 1918.5 nm and 2031 nm by adjusting the intra-cavity waveplates. When the wavelength is tuned to below 2000 nm, the average output power exceeds 1 W. The oscillator provides a maximum average power of 1.314 W (corresponding to a pulse energy of 2.58 nJ) and a highest peak power of 12.5 kW at 1940 nm. Such a high-power, tunable 2-µm mode-locked fiber laser is an ideal light source candidate for a variety of applications, such as frequency metrology, molecular spectroscopy, and ultrafast pump-probe spectroscopy.

All-polarization-maintaining NALM mode-locked Er/Yb-doped large-mode-area fiber oscillator.

We report a mode-locked high-power all-polarization-maintaining Er/Yb-doped large-mode-area fiber oscillator based on a bias nonlinear amplifying loop mirror (NALM). The oscillator can generate ∼1-nJ femtosecond pulses without dispersion compensation. By inserting a Martinez-type compensator to provide normal dispersion, it can generate >10-nJ picosecond dissipative solitons (DSs). The measured M2 factors are below 1.5, indicating a good beam quality. When the cavity dispersion is tuned to be ∼0.704 ps2, the oscillator can deliver chirped DSs with an average power as high as 690 mW at a repetition rate of 49.86 MHz, corresponding to a pulse energy of ∼13.8 nJ. The pulse after compression has a near Fourier-limited width of ∼2 ps. Successful demonstration of this laser provides a robust scheme for improving the performance of ultrafast fiber lasers in average power and pulse energy.

Generation of few-cycle pulses from a mode-locked Tm-doped fiber laser.

We report a compact, self-starting dispersion-managed mode-locked thulium-doped fiber oscillator that delivers 2.6 nJ pulses at 2 µm with a repetition rate of 250 MHz. The average output power and spectral bandwidth of the pulses reach impressive values of 648 mW and 103 nm, respectively. The generated pulses are near linearly chirped, capable of linearly compressing to 74 fs in a normal dispersion fiber after power attenuation. Using a nonlinear fiber compression scheme can even compress the pulses to 29 fs (4.3-cycle). The remaining pulse energy is 1.15 nJ, and the corresponding peak power is estimated as 39.4 kW. To the best of our knowledge, this is the first demonstration of nonlinearly compressing the pulse of a 2 µm fiber oscillator to the sub-5 cycle regime. Such a few-cycle fiber laser could be an ideal candidate source for short-wavelength mid-infrared frequency metrology and molecular spectroscopy applications.