Experimental Study of Stimulated Raman Scattering in the Hundred-Picosecond Pulse Double-Clad Fiber Amplifier

In this paper, the amplification of the hundred- picosecond pulse with 1Kz repetition rate is presented experimentally in the Ytterbium-doped double-clad fiber amplifier, whose active fiber core has a diameter of 6.5um with numerical aperture of 0.12. When the pulse peak power is up to 20kW and the gain of amplifier is about 29dB, the stimulated Raman scattering (SRS), the main limitation for achieving high output pulse peak power for hundred-picosecond pulse amplification, appears. To overcome the difficulty of measuring the spectrum of SRS in our limited lab condition, the long single mode (SM) fiber with positive group velocity dispersion is employed to separate the signal and SRS pulses. The fiber Bragg grating is also adopted to further testify. The wavelength shift of SRS obtained by the proposed method is about 50nm for the pulse signal of wavelength 1053nm, in good agreement with the theoretical estimation.