Experimentally investigate the nonlinear amplifying process of high power picoseconds fiber amplifier

Abstract

The combination of laser amplification and nonlinear properties is the unique and special character of the fiber amplifier. In this paper, we power amplify picoseconds seed source with an all-fiber MOPA chain. The main purpose of this work is not to scale picoseconds laser power to an extremely high value but also to observe the nonlinear amplifying process within the high power picoseconds fiber amplifier. By altering the repetition rate of the seed pulse, corresponding to the peak power of the pulse, we compare the output properties of the high power picoseconds fiber amplifier. More than 50W Raman-dominated broadband continuum has been demonstrated at a pulse repetition rate of 60MHz. Anti-stokes spectral components and four wave mixing (FWM) are observed at a pulse repetition rate of 480MHz. The output spectrum of picoseconds pulse is slightly broadened due to self-phase modulation (SPM) and yields as high as 71.3W picoseconds laser output at a pulse repetition rate of ∼1GHz. These results indicate that the fiber amplifier could be used not only as a conventional power amplifier but also as a nonlinear spectra convertor under some special condition. A potential application is that fiber amplifier could be directly utilized as a high power cladding pumped supercontinuum source using the nonlinear amplifying process within the active fiber.