Stretcher-free high energy nonlinear amplification of femtosecond pulses in rod-type fiber

We report on the generation of high energy ultrashort pulses with a compact and simple stretcher-free single stage rod-type fiber amplifier in the nonlinear regime. By addition of a compact single grating compressor to compensate for the dispersion produced in the amplifier, pulses as short as 49 fs with 870 nJ pulse energy and 12 MW peak power are obtained, with a 1250 l/mm grating and higher quality pulses of 70 fs, 1.25μJ pulse energy and 16 MW peak power are generated with a 1740 l/mm grating.