1700 nm and 1800 nm band tunable thulium doped mode-locked fiber lasers

Raman dissipative soliton source of ultrashort pulses in NIR-III spectral window

We present a novel fiber source of ultrashort pulses at the wavelength of 1660 nm based on the technique of external cavity Raman dissipative soliton generation. The output energy of the generated 30 ps chirped pulses is in the range of 0.5-3.6 nJ with a slope efficiency of 57%. Numerical simulations are in excellent agreement with the experimental results and the shape of the compressed pulses. The compressed pulses consist of a central part with a duration of 300 fs and a weak pedestal. Our results clearly demonstrate the potential to extend the spectral range of the Raman-assisted technique for generating ultra-short pulses to new frequency regions, including biomedical windows. This paves the way for the development of new dissipative soliton sources in these bands.

Tunable dissipative soliton Tm-doped fiber laser operating from 1700 nm to 1900 nm

In this Letter, we demonstrate an ultrabroadband (1700-1900 nm) tunable Tm-doped fiber laser (TDFL) generating dissipative solitons in the net-normal dispersion regime. The laser delivers pulses with spectral widths ranging from 10 nm to 23 nm and pulse durations from 8.7 ps to 18.3 ps. Stretched-free pulse amplification at the gain edge (1708 nm) and gain peak (1807 nm) is implemented to demonstrate the range of further power scalability of the laser signal. The maximum achieved power in a one-stage Tm-doped amplifier is 140 mW with a compressed pulse duration of 478 fs. Considering the diverse utility of this wavelength band, this laser is highly desirable for applications such as optical sensing, biological imaging, and industrial machining.

1.7 µm - 1.73 µm tunable ultrafast Raman fiber laser pumped by 1.6 µm dissipative soliton pulses

Here, we report an all-fiber tunable ultrafast Raman laser synchronously pumped by a home-made 1.6 µm dissipative soliton (DS) picosecond (ps) laser, which produces Stokes light beyond 1.7 µm. The Raman gain medium is a segment of highly germanium-doped (Ge-doped) fiber offering a high Raman gain coefficient at the target wavelength. Once the Raman conversion cavity is synchronized with the pump light, a stable 1.7 µm Raman laser (the first Stokes light) can be obtained at a low pump threshold. The maximum output power of the 1.7 µm Raman laser can reach ∼ 22.62 mW. The wavelength tuning operation is independent of tunable pump source and intra-cavity filter. By adjusting the intra-cavity delay line simply, the different spectral component within the broad Raman gain bandwidth can be selectively synchronized with the pump light so that the Raman laser wavelength can be tuned continuously from 1702.6 nm ∼ 1728.84 nm. This tunable 1.7 µm waveband ultrafast laser will have potential applications in multiphoton microscopy for e.g. deep bio-imaging.

All-fiber short-wavelength tunable mode-locked fiber laser using normal dispersion thulium-doped fiber

We report an all-fiber high pulse energy ultrafast laser and amplifier operating at the short wavelength side of the thulium (Tm) emission band. An in-house W-type normal dispersion Tm-doped fiber (NDTDF) exhibits a bending-induced distributed short-pass filtering effect that efficiently suppresses the otherwise dominant long wavelength emission. By changing the bending diameter of the fiber, we demonstrated a tunable mode-locked Tm-doped fiber laser with a very wide tunable range of 152 nm spanning from 1740 nm to 1892 nm. Pulses at a central wavelength of 1755 nm were able to be amplified in an all-fiber configuration using the W-type NDTDF, without the use of any artificial short-pass filter or pulse stretcher. The all-fiber amplifier delivers 2.76 ps pulses with an energy of ∼32.7 nJ without pulse break-up, due to the normal dispersion nature of the gain fiber, which marks so far, the highest energy amongst fiber lasers in the 1700 nm-1800 nm region.