Scientists from the Helmholtz-Institute Jena and the Friedrich-Schiller-University Jena have reached a new milestone: After a significant upgrade of the laser system POLARIS carried out in 2015, its maximum output energy after the final amplifier could be increased by more than a factor of three. POLARIS is a high-power laser system employing Yb-doped solid state laser materials which are entirely pumped by high-power laser diodes which both promises a high wall plug efficiency and a high repetition rate. The recent improvement in pulse energy became possible both by a reconfiguration of POLARIS’ amplifier design and by an improvement of the performance properties of the amplification crystals in the last amplifier. The achieved pulse energy of 54.16 Joules sets a new world record for a fully diode-pumped, high-power laser system, which is based on the technique of chirped-pulse amplification (CPA).
In addition to this improvement in energy, a reduction in pulse duration could be achieved by carefully pre-shaping the wavelength spectrum of the amplified pulses. The output spectrum of the pulses centered at 1030 nm now reaches a bandwidth of more than 20 nm (FWHM), which can support a final pulse duration of less than 100 fs after amplification. While the maximum peak power of the laser pulses, which can currently be generated by POLARIS to be used in high-intensity experiments, e.g. on particle acceleration, is limited by the final pulse compressor to 200 TW, this clearly shows the potential of this laser concept.
POLARIS is one of the central large-scale infrastructures operated by the Helmholtz-Institute Jena. It is used for high-intensity experiments on particle acceleration and generation of ultra-short pulses of secondary radiation. Furthermore, the POLARIS laser system is a testbed for other solid-state diode pumped laser systems. The results achieved with POLARIS are therefore very promising for upcoming laser systems like PENELOPE operated at HZDR in Dresden or PHELIX at GSI in Darmstadt, which can be improved based on the recent results achieved at POLARIS in Jena.