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.