High-efficiency self-frequency-shifted solitons generation in an erbium-doped fiber laser system

We demonstrate here high-efficiency self-frequency-shifted soliton generation in standard single-mode fiber (SMF). Pulse with 80.96-MHz repetition rate passing through a length of 5.5-m fiber, Raman soliton with an energy of as much as 4.8 nJ was generated by pump pulse with an energy of 5.7 nJ, corresponding to an efficiency of nearly 85 %. Wavelength shifting of Raman soliton is fully investigated by controlling the input pulse energy, fiber length, and polarization state, resulting over 440 nm wavelength tuning range 1600–2040 nm. As the length of SMF is shortened to 0.5 m, Raman soliton pulses with energy and pulse duration of 3 nJ, 80 fs at 1700 nm and 6 nJ, 75 fs at 1820 nm are generated respectively, and the output average power keeps stable with a root-mean-square value of 0.7 % in four hours measurement. The proposed demonstration provides an easy-to-build, stable, high efficiency tunable laser source for multiphoton imaging.