Nonlinear Regenerative Amplifier with Net Negative Nonlinearity for Ultrashort-Pulse Generation

We exploit self-defocusing nonlinearity from phase-mismatched second-harmonic-generation for nonlinear spectral broadening in a Yb:YAG thin-disk regen. We demonstrate direct amplification of 10-μ J, 1.2-ps pulses to 0.47 mJ with broadened spectrum that can support <400-fs pulses.