Sub-100 fs pulses with 12.5-W from Yb:CALGO based oscillators

We report on the generation of 94-fs pulses with 12.5-W average output power from an 80-MHz Yb³⁺:CaGdAlO₄(Yb:CALGO) oscillator with pulse energies and peak power levels higher than 150-nJ and 1.45-MW, respectively. To the best of our knowledge, this is the highest average power ever reported for a sub-100-fs bulk oscillator. Average output power levels higher than 10-W were also achieved in lower repetition rate oscillators at 23.7 MHz and 42.5 MHz with pulse durations ranging from 141-fs to 323-fs and corresponding pulse energies as high as 0.42 μJ. In all experiments stable and self-starting mode-locking with transform-limited pulses and beam quality factors better than M²<1.1 were achieved. Continuous tunability in mode-locked operation between 1026-nm and 1052-nm was also demonstrated. We believe that shorter pulses at higher average output powers should be possible and - combined with extended cavities - such laser systems could reach the μJ pulse energy level with peak powers in the 10-MW regime.