High power femtosecond 1030nm burst-mode front-end and pre-amplifier for the European XFEL pump-probe laser development

Summary form only given. The successful implementation of superconducting LINAC technology at the European XFEL will boost the time averaged X-ray power density substantially above current values, operating at repetition rates of up to 4.5MHz. However, this high pulse rate will occur during 600μs long bursts at 10Hz repetition rate, resulting in up to 27000 pulses per second. Picosecond lasers such as the injector-laser, and the pump-probe femtosecond lasers used in experiments will need to match this burst-mode emission pattern. There are currently no “off-the-shelf” commercial femtosecond laser technologies producing this kind of output at close to mJ-level energies per pulse and sub-20fs pulse width. Therefore, at the European XFEL, a development project was launched in order to close this gap in time for the start of operation in 2016. We present the design and performance of an all-fiber burst-mode chirped-pulse front-end amplifier (CPA), seeding the Yb:YAG pre-amp of the power amplifier-chain for the pump pulses of a non-collinear parametric amplifier (NOPA), also operating in burst-mode. The pre-amplifier is based on the Yb:YAG InnoSlab technology, boosting the burst output power comfortably up to 500W at pulse widths <;800fs. The operatingpoint of the pre-amp lies at 400W output, leaving substantial head room. The design of subsequent stages, based on scaled-up InnoSlab technology, aims at >20kW. The front-end provides a second burst-mode output of 300fs pulses and μJ-level pulse energy, used to generate synchronized super-continuum for seeding of the NOPA. Although there have been reports of fiber amplifiers, producing bursts of femtosecond pulses, the performance level of these designs is well below the stringent requirements for the European XFEL (compressibility, pulse and burst stability, repetition rate). Similarly, high power 1kW-level amplification of subpicosecond pulses using InnoSlab or thin-disk technology has been shown. However, we show for the first time a strictly burst-mode, multi-MHz and down to 100kHz-level intra-burst rep-rate, all-in-fiber front-end and high gain short gain-length pre-amp, capable of operating at constant power.