790–1000 nm continuously-tunable fiber-based femtosecond laser source

Abstract

We report a 790–1000 nm tunable femtosecond laser source by second harmonic generation (SHG) of a 1580–2000 nm soliton self-frequency shift (SSFS) fiber laser. The SSFS fiber laser with an all polarization-maintaining fiber configuration consists of passively mode-locked figure-9 Er-doped fiber oscillator, two-stage fiber amplifiers and a nonlinear fiber, delivering femtosecond Raman solitons in a tunable range of 1580 to 2016 nm. The tunable Raman solitons are further injected into a specifically-designed chirped periodically-poled lithium niobite (CPPLN) crystal for efficient SHG, and therefore femtosecond pulses with wide wavelength tuning from 790 to 1000 nm are obtained. The shortest pulse duration is < 100 fs at 890 nm, and the average power is 7.55 mW with a repetition rate of 44.9 MHz. This is, to the best of our knowledge, the first demonstration of a < 1000 nm broadband tunable fiber-based femtosecond source almost covering the whole short-wavelength near-infrared spectrum, which may have important applications in the nonlinear microscopy, biomedical imaging, and material processing.