Generation of 15 nJ pulse energy by a sub-150 fs thulium-doped fiber Mamyshev oscillator.

Mamyshev oscillators have pushed the frontiers in output parameters of ytterbium- and erbium-based ultrafast fiber oscillators in the spectral region around 1 µm and 1.5 µm within the last few years tremendously. In order to expand the superior performance toward the 2 µm spectral region, we present in this Letter an experimental investigation of the generation of high-energy pulses by a thulium-doped fiber Mamyshev oscillator. Generating highly energetic pulses is enabled by a tailored redshifted gain spectrum in a highly doped double-clad fiber. The oscillator emits pulses with an energy of up to 15 nJ, which can be compressed to 140 fs.

Ultrafast, stretched-pulse thulium-doped fiber laser with a fiber-based dispersion management.

An ultrafast thulium-doped fiber laser with stretched-pulse operation has been realized and investigated. The passively mode-locked oscillator emitted 119 fs pulses at a peak wavelength of 1912 nm. A normal-dispersion fiber with a high numerical aperture and small core was used for intracavity dispersion management and external compression. Numerical simulations were performed and are in good agreement with the experimental results.

Monotonically chirped pulse evolution in an ultrashort pulse thulium-doped fiber laser.

We report on monotonically positively chirped pulse operation of a hybridly mode-locked thulium fiber laser. Dispersion management was realized with a small-core, high-NA fiber providing normal dispersion in the 2 µm wavelength region. The laser delivered pulses with 0.7 nJ energy at the 1927 nm center wavelength and sub-500-fs pulse duration after compression.

Pulse characteristics of a passively mode-locked thulium fiber laser with positive and negative cavity dispersion.

We investigated of the output characteristics of a spectrally filtered stretched-pulse thulium fiber laser in dependence of cavity dispersion and pump power. The experimental results together with corresponding theoretical modeling allow for a deeper insight into the pulse shaping mechanisms.

Pulse energy of 151 nJ from ultrafast thulium-doped chirped-pulse fiber amplifier.

We report on chirped-pulse amplification of an ultrafast thulium-doped fiber laser. Pulses with an energy of 3.3 nJ and a bandwidth-limited pulse duration of 195 fs could be amplified to 151 nJ, which corresponds to an average power of 5.7 W at 37.6 MHz pulse repetition rate. The maximum output power was limited by the available pump power. The pulses could be dechirped to a duration of 258 fs.

Stretched-pulse operation of a thulium-doped fiber laser.

We report on stretched-pulse operation of a thulium-doped fiber laser. The laser generated pulses at a center wavelength of 1974 nm with an energy of 4 nJ that could externally be compressed to a duration of 173 fs.

Wavelength resolved intracavity measurement of the cross sections of a Tm-doped fiber.

The wavelength dependent measurement of the relaxation oscillation frequency in a laser oscillator allows the study of the three- and four-level nature of the active material. Accordingly we present a tunable thulium doped fiber laser that covers the transition from three- to four-level operation at 2025 nm, characterized by the vanishing occupation of the terminal laser level. The laser is tunable from 1864 nm to 2075 nm with a linewidth below 0.3 nm. A maximum output power of 3.8 W at 1930 nm was achieved with a slope efficiency of 33.6% and an absorbed pump power of 17.5 W. Absorption and emission cross sections were derived over the tuning range by an intracavity measurement method.

Ultrafast thulium-doped fiber-oscillator with pulse energy of 4.3 nJ.

A femtosecond fiber laser based on thulium-doped double-clad silica fiber with an internal dispersion compensation is presented that generates pulses at a center wavelength of 1976 nm with an energy of 4.3 nJ and a duration of 1.2 ps. The dechirped pulse duration is 294 fs. The pulse energy is more than 2 orders of magnitude above the pulse energy demonstrated previously. Mode locking is achieved using additive pulse mode locking, and dispersion compensation is facilitated by a grating stretcher arrangement.