Femtosecond tunable solitons up to 4.8 µm using soliton self-frequency shift in an InF3 fiber.

A tunable ultrashort soliton pulse source reaching up to 4.8 µm is demonstrated based on a 2.8 µm femtosecond fiber lasercoupled to a zirconium fluoride fiber amplifier followed by a small core indium fluoride fiber.This demonstration is extendingby 500 nm the long wavelength limit previously reported with soliton self-frequency shift (SSFS) sources based on fluoridefibers. Our experimental and numerical investigation highlighted the spectral dynamics associated with the generation of highlyredshifted pulses in the MIR using SSFS enhanced by soliton fission. This study is intended at providing a better understandingof the potential and limitations of SSFS based tunable femtosecond fiber sources in the 3-5 µm spectral range.