Image. The team in Jena developed the world-record laser system based on a fs fiber laser and two nonlinear compression stages. Transfer to ELI ALPS is scheduled for February 2017. (Photo courtesy Fraunhofer IOF)
With the goal of developing a new source for high-repetition-rate ultrashort pulses, researchers in Jena have joined with the Extreme Light Infrastructure (ELI) to build a laser system that delivers more than 200 W of 6 fs pulses, a world record. The team consist of researchers from the Friedrich Schiller University, the Fraunhofer Institute for Applied Optics and Precision Engineering IOF, and Active Fiber Systems GmbH.
The system is based on a femtosecond fiber laser with two nonlinear compression stages. The pump source incorporates a fiber chirped-pulse amplification (FCPA) system with a coherent combination of up to eight main amplifier channels. For first tests, the system was run at 1.27 MHz, delivering 660 W. The final specification will be 100 kHz and 100 W.
The two nonlinear compression stages are based on noble-gas-filled capillaries. The first stage delivered pulses of about 30 fs at 408 W (corresponding to 320 µJ pulse energy). After the second stage and a subsequent compression, 208 W of 6.3 fs pulses were achieved. This corresponds to less than two cycles at a center wavelength of 980 nm. The waveguiding of the capillaries led to an excellent beam profile. Detailed results were published in Optics Letters.
Next Steps Toward a 24/7 User Facility
The team in Jena is developing the laser system for the ELI Attosecond Light Pulse Source (ELI-ALPS) in Szeged, Hungary. The published results are derived from the first development phase of the high-repetition-rate ALPS light source. The target specifications are 1 mJ energy at 100 kHz repetition rate—and the pulse length should be kept at approximately 6 fs. Based on recent progress in the lab, the team in Jena is optimistic it will deliver the system with these specifications in February 2017.
The current specifications are unprecedented, but the final version in Szeged will be even stronger. In a second step, it will be upgraded to higher energies of 5 mJ. It will be used to create high-repetition-rate attosecond pulses (1 as is 10-18 s). These pulses will allow researchers to follow electron motions in real time, which will enable essential progress in fields such as atom and molecule physics, and in solid-state physics and new disciplines such as plasmonics.
The ELI is funded by more than 850 million euros from the European Regional Development Fund (ERDF). With separate institutes in the Czech Republic, Hungary, and Romania, the ELI will begin as a user facility in 2018.
Image. The new ELI ALPS facility in Szeged, Hungary, will start as a user facility in 2018. (Photo courtesy ELI ALPS)