Current status of the PEnELOPE project

With the first demonstration of direct diode-pumped TW lasers with pulse energies of 1 J and more a scaling of this approach for use in PW-class laser systems became feasible. The Helmholtz-Centre Dresden-Rossendorf is now planning to build a fully diode-pumped Petawatt laser for laser-particle acceleration research. Within the PEnELOPE project (Petawatt, Energy-Efficient Laser for Optical Plasma Experiments) a pulse energy of 150 J, a repetition rate around 1 Hz and a pulse duration of 150 fs after compression are desired. In order to minimize the required pump peak power and therefore the initial costs a broad-band Ytterbium doped laser material with a long fluorescence lifetime (i.e. Yb:glass or Yb:CaF2) is chosen. A total pump peak-power of 1.2 MW is scheduled assuming a pump pulse duration of 2 ms and an envisioned optical-to-optical conversion efficiency of 10% before compression. Pulses as short as 60 fs having an energy of 25 nJ are generated in a commercial Yb:KGW oscillator at a center wavelength of 1035 nm. In order to employ CPA technique the pulses are stretched to 2 ns in a grating stretcher having grating constant of 1760 lines per mm. The amplifier-chain consists of a regenerative amplifier and 4 subsequent multipass amplifiers. While the regenerative amplifier produces a gain 40.000 gain narrowing is required to be suppressed by intra-cavity spectral shaping. At the sub-mJ energy level a bandwidth of 25 nm was achieved out of the regenerative amplifier. Two booster amplifiers with an energy of 100mJ and 1J output were also demonstrated. The full amplifier system will consist of two more multipass amplifiers each having a gain of 10-16 in order to achieve the desired pulse energy.