Ultrafast fiber lasers using coherent combination: TW pulses at 100 kHz and beyond (Conference Presentation)

The timeframe between the first demonstration of novel laser parameters and the commercial availability of systems delivering those parameters has been shrinking over the recent years. This development makes femtosecond laser systems with unparalleled parameters available to a wide range of applicants. We present the progress in setting up such a FCPA laser system delivering 5mJ pulse energy at 100kHz pulse repetition rate (i.e. 500W of average power) and with pulse durations of 6fs. The system, the so-called HR2 laser, will be implemented at the ELI-ALPS facility in Szeged, Hungary. Furthermore, the laser is optimized to generate output pulses with a stable carrier-envelope-phase (CEP). Since 6fs requires a bandwidth not supplied by Yb-based gain-media, and thus nonlinear compression is necessary, the chirped-pulse-amplification (CPA) system itself must deliver a higher energy to compensate for the losses in these nonlinear-compression-stages. Hence, the CPA is operated at 12mJ and 1.2kW delivering sub 300-fs pulses with an almost diffraction limited beam quality. To achieve such a parameter-set, the output of 16 main-amplifier channels is coherently combined using a polarization-based filled-aperture combining scheme. Maintaining the CEP stability of the oscillator throughout the entire system is another key challenge of the project. We finally discuss further power-scaling approaches and possibilities to reduce system size, complexity and, therewith, cost. By using these revolutionary laser systems, even demanding applications such as laser-based particle acceleration or XUV-generation via high-harmonic generation will be able to perform the important step from the laboratory to real-world applications allowing to access repetition rates orders of magnitude higher than before.