Many industrial and scientific applications need ultra-short and energetic pulses. Diode-pumped systems based on
ytterbium-doped crystals have a huge interest thanks to their good thermal and spectroscopic properties. Among them,
Yb:CaF2, shows very promising results for short pulse generation, and its long fluorescence lifetime, 2.4 ms, indicates a
high energy storage capacity.
We present a diode-pumped regenerative amplifier based on an Yb:CaF2 crystal optimized to produce short pulses for
various repetition rates ranging from 100 Hz to 10 kHz. The experiment is performed with a 2.6-% Yb doped 5-mm-long
CaF2 crystal grown by using the Bridgman technique and used at Brewster angle. To optimize the injection pulse
spectrum in terms of bandwidth and maximum gain, the seed pulses are generated by a broadband Yb:CALGO oscillator
centered at 1043 nm with a FWHM bandwidth of 15 nm at a repetition rate of 27 MHz. The pulses are then stretched to
260 ps with a transmission grating. The shortest pulse duration generated is 178-fs, and the corresponding energy is
1.4 mJ before compression (620 μJ after), at a repetition rate of 500 Hz for 16 W of pump power. The bandwidth is 10
nm centered at 1040 nm. At 10 kHz repetition rate, 1.4 W of average power before compression is obtained,
corresponding to an optical-optical efficiency of 10%. We also noticed that the pulse duration tends to increase above 1
kHz, reaching 400 fs at 10 kHz.