High-energy multiwatt femtosecond diode-pumped Yb:CaAlGdO4and Yb:CaF2regenerative amplifiers

We study and compare the performance of Yb:CaAlGdO4- and Yb:CaF2-based regenerative amplifiers at low (5 to 10 kHz) and high (up to 500 kHz) repetition rates. Both materials allow for pulse energies of <1 mJ with sub-400-fs at low repetition rates and up to 9.4 W of average output power at 500 kHz. Thanks to the good thermal properties of Yb:CaF2 and Yb:CALGO, the extracted energy has the potential to be significantly increased with further pump power scaling. Shorter pulses are also potentially achievable by optimizing the design of stretcher and compressor in order to better compensate higher-order dispersion and reduce nonlinear effects.