A new high-performance Yb:CaAlGdO(4) (Yb:CALGO) regenerative amplifier is demonstrated. Pumped by 116 W at ≈980 nm and seeded by means of a 92 fs oscillator, it generates as much as 36 W of average output power with chirped pulses, and 28 W with 217 fs compressed pulses at 500 kHz repetition rate. This corresponds to 56 μJ of pulse energy and 258 MW peak power. The compressed pulses have a time-bandwidth product of 0.69 and could be shortened further with an improved compressor setup.

We investigated and compared Yb:CaAlGdO4 and Yb:CaF2 regenerative amplifiers at repetition rates 5-10 kHz, a frequency range interesting for industrial applications requiring relatively high pulse energy. Both materials allow for pulse energies close to 1 mJ with sub-400-fs pulses. The two laser materials offer comparable performance in the pump power range investigated. The same regenerative amplifiers can be run up to 500 kHz for much faster material processing, with maximum output power of up to 9.4 W.

Raman conversion with a single Ba(NO 3 ) 2 crystal (barium nitrate) either in single-and double-pass travelling-wave setups has been investigated. A Master-OscillatorPower-Amplifier (MOPA) system, based on a passively Q-switched (PQS) laser generating 500-ps pulses and delivering a total energy of 350 µJ at 1 kHz, was used as pump source for the Raman generator. The two-passes setup yielded 116-µJ, 150-ps Fourier-and diffraction-limited pulses at 1198 nm for ≈3× the Raman threshold with no additional Stokes lines, and conversion efficiency of 35%. Such results are interesting not only for direct applications of the wavelength-shifted laser source, but also for further pulse-compression and supercontinuum generation in fibers. Indeed, self-phase modulation up to 0.82 nm has been demonstrated (pulse compression down to 5 ps) as well as 120-nm supercontinuum.

We report on a femtosecond high-power regenerative amplifier based on Yb:Lu₂O₃. Exploiting the excellent thermo-mechanical properties of this material, we were able to achieve up to 64.5 W in continuous-wave regime, limited only by the available pump power. In pulsed operation, 42 W of average output power at a repetition rate of 500 kHz with 780 fs long pulses could be demonstrated, resulting in a pulse peak power of ∼100  MW. The spectrum was centered at 1034 nm with an FWHM of 2.4 nm, potentially allowing for even shorter pulses. At the maximum output power the beam was nearly TEM₀₀, with an M² value of 1.2 in both axes.