High-energy and efficient Raman soliton generation tunable from 1.98 to 2.29 μm in an all-silica-fiber thulium laser system

We demonstrate a compact, all-fiber-integrated laser system that delivers Raman solitons with a duration of ∼100 fs and pulse energy of up to 13.3 nJ, continuously wavelength tunable from 1.98 to 2.29 μm via Raman-induced soliton self-frequency shift (SSFS) in a thulium-doped fiber amplifier. We realize a >90% efficiency of Raman conversion, the highest reported value from SSFS-based sources, to the best of our knowledge. This enables us to achieve >10 nJ soliton energy from a 2.16 to 2.29 μm range, the highest energy demonstrated above 2.22 μm from an SSFS-assisted, all-fiber tunable single-soliton-pulse source, to the best of our knowledge. Our simple and compact all-fiber tunable laser could serve as an efficient ∼2 μm femtosecond source for a wide range of mid-infrared applications.