Sub-100-fs Yb:CALGO nonlinear regenerative amplifier

We report on the first diode-pumped Yb:CaGdAlO4 regenerative amplifier in the sub-100-fs regime. It generates pulses at a central wavelength of 1047 nm with up to 24 μJ energy (after compression) at a repetition rate of 50 kHz. The measured pulse duration is 97 fs, with a spectral bandwidth of 19 nm. We describe in detail how nonlinear effects are optimally used to compensate gain narrowing in order to overcome the 100 fs barrier.