High Repetition Rate Yb:CaF₂ Multipass Amplifiers Operating in the 100-<roman>mJ</roman> Range

Abstract

We present the research advances on the development of 50-200 mJ energy range diode-pumped Yb:CaF 2based multipass amplifiers operating at relatively high repetition rates. These laser amplifiers are based on diverse innovative geometries. All these innovations aim to design compact, stable and reliable amplifiers adapted to our application that consists in pumping ultrashort-pulse OPCPA (optical parametric chirped pulse amplifier) systems in the frame of the Apollon 10 PW laser project. The targeted repetition rate is in the range of 20-100 Hz with energies of few tens of mJ for the first stages up to 1 J for the final stage. An analysis of the specificities of Yb:CaF 2 is done to explain the different options we chose to fulfil these specifications. The critical points and limitations of the multipass Yb:CaF 2-based amplifiers are subsequently discussed. To overcome the encountered problems, different issues are investigated such as crystal optimisation, laser head geometry, thermo-optical dynamics or coherent combining techniques. Experimental results for different multipass configurations are demonstrated and discussed.

The Apollon 10 PW laser: experimental and theoretical investigation of the temporal characteristics

“…More details on the Apollon OPCPA and in particular on the OPCPA-pump challenges are given in Refs. [6][7][8][9][10][11][12][13].…”

A compact 20-pass thin-disk multipass amplifier stable against thermal lensing effects and delivering 330 mJ pulses with M² < 1.17

“…Most thin-disk multipass amplifier designs are based on three main categories: relay-imaging (4f-imaging) [4][5][6][7][8][9], quasi-collimated propagation (lens guide) [10][11][12][13][14] or resonator-based optical Fourier transform (FT) propagations [15][16][17]. In 4f-based designs, the beam is imaged from active medium (AM) to active medium so that its size remains constant for each pass (if soft aperture effects are neglected).…”

A compact 20-pass thin-disk multipass amplifier stable against thermal lensing effects and delivering 330 mJ pulses with M² < 1.17

“…Most thin-disk multipass amplifier designs are based on three main categories: relay-imaging (4f-imaging) [4][5][6][7][8][9], quasi-collimated propagation (lens guide) [10][11][12][13][14] or resonator-based optical Fourier transform (FT) propagations [15][16][17]. In 4f-based designs, the beam is imaged from active medium (AM) to active medium so that its size remains constant for each pass (if soft aperture effects are neglected).…”