High-energy 1.96-2.4 μm tunable Raman soliton generation in all-silica-fiber Tm-doped amplifier

Femtosecond pulses in the 2-2.4 μm spectral region have potential applications in many fields, such as two-photon fluorescence imaging, sensitive molecular spectroscopy, and nonlinear laser system. As the energy is proportional to the square of the soliton order, the high-energy soliton pulse can be achieved by promoting the soliton order during the soliton splitting and soliton self-frequency shifting processes. We demonstrated high-energy Raman solitons with wavelengths tunable from 1.96 to 2.39 μm in a thulium-doped silica fiber amplifier. The maximum pulse energy of the soliton was about 65.1-nJ with the corresponding wavelength of 2.39 μm, which, to our knowledge, was the farthest and the highest energy soliton pulse generated in commercial single-mode silica fiber.