Broadband and intense coherent light sources
The predecessor of Research Area A.1 in the first funding period (1st fp) of MAP, A.1: “Next generation light sources”, resulted in significant advances in femtosecond laser technology by the development of tools for the generation of few-cycle, waveform-controlled, unprecedentedly broadband, powerful laser pulses. In what follows, we briefly review the most important goals, results and implications of Area A.1 in the 1stfp.
• In the project entitled “Powerful lightwave synthesis at the full repetition rate of oscillators” (A.1.1) we aimed at developing a light source which, operating at the full repetition rate of an oscillator, is capable of delivering ultrashort pulses with kilowatt average power. Thanks to a long-standing collaboration between the groups of T. Hänsch and F. Krausz, we achieved several world records in enhancement cavity technology including record peak power of > 1 GW at 18-kW average power and 200-fs pulse duration and record average power of 72 kW at 2-ps pulse duration [A1.4] . The new cavity technology has been successfully applied to generate frequency combs in the XUV by intra-cavity high harmonic generation [A1.21]. However, the achievable output powers are still insufficient for the original goal of XUV high-resolution spectroscopy. New strategies for resolving the remaining challenges of efficient XUV extraction from the enhancement cavity and a cavity design which is able to sustain the required high seeding-comb intensity will be further investigated in the forthcoming funding period. Furthermore, we developed a 6-µJ, 1-ps Yb:YAG oscillator operating at 10-MHz rate which – after frequency doubling – we successfully applied for the generation of sub-10-fs, 0.5-µJ NIR laser pulses via broadband optical parametric amplification (OPA). In an alternative approach, a fibre/chirped-mirror compressor was seeded with a 500-nJ Ti:Sa oscillator to generate 16-fs, 0.35-µJ pulses at 5-MHz repetition rate [A1.1]. These results constitute the basis for the pursuit of goals A.1a-c in the forthcoming funding period.
• In projects A.1.2, A1.3, light-waveform control in combination with the generation of the shortest attosecond pulses to date has enabled MAP researchers to observe atomic-scale electron motion in real time [A1.28]. These and related achievements are highlighted in the description of Research Area B.3 because the pursuit of related goals will be continued there.
• Scaling waveform-controlled light pulses to ultrahigh peak power has been pursued by the development of the Petawatt Field Synthesiser (PFS) at MPQ [A1.3, A1.11, A1.19, A1.26, A1.27]. Based on the novel scheme of short-pulse-pumped optical parametric chirped-pulse amplification (OPCPA), PFS aims at delivering few-cycle pulses at PW-scale peak powers and constitutes a basic technology for the billion-euro-scale Pan-European installation: Extreme Light Infrastructure – ELI . Unfortunately, progress on PFS (funded entirely by the Max-Planck Society) has been slower than expected. Thus, the system is still in the construction phase and could not be used for MAP experiments as planned. However, in the meantime, the large technological issues, such as the architecture of a common frontend for pump and OPCPA seed [A1.11], 50-J picosecond pump laser design [A1.3, A1.26, A1.27], the suitability of thin DKDP crystals for short-pulse-pumped OPCPA [A1.19] have been successfully demonstrated, proving the feasibility of the approach. Completion of the system is expected before the end of 2012. Meanwhile, PFS’ predecessor, the world’s first multi-terawatt few-cycle source: LWS-10 (8 fs, 130 mJ @ 850 nm, 10 Hz) [A1.12] has been applied to several first-of-their-kind experiments such as few-cycle-driven electron acceleration and high harmonic generation from solid surfaces as well as from atomic gas targets . The latter experiments hold promise for the generation of gigawatt-peak-power isolated attosecond pulses, which would open a new chapter in attosecond science. This goal, along with the completion of PFS-pro, the kHz-version of PFS, is further pursued in the forthcoming funding period of MAP.
• Project A1.4 entitled “Ultra-wideband instrumentation” proved to be essential for creating and advancing MAP’s basic infrastructure. In the forthcoming funding period it is supplemented with several other projects to form a separate Research Area A.2 dedicated to technology development and will be discussed there in detail.
Our long-term goals and visions
The success in the pursuit of the MAP grand goals (along with many other objectives beyond the scope of MAP) critically relies on the significant advancement of femtosecond laser technology beyond the current state of the art. The research collaborations established in MAP along with CALA and the relevant know-how available at Garching/Munich promise to strengthen our leadership in pushing the frontiers of femtosecond, attosecond and high-power laser technologies. Leading the world in this technological progress will not only create ideal conditions for the pursuit of MAP’s grand goals, but also allow MAP researchers to be among the first to identify new application frontiers.
A.1.1 | High-power sub-MHz-rate femtosecond VIS-MIR sources (Alexander Apolonskiy)
A.1.2 | XUV frequency combs (Thomas Udem)
A.1.3 | Enhancement cavity for BRIX (Ernst Fill)
A.1.4 | PFS pro – a kHz, sub-PW, few-cycle source (Zsuzsanna Major)
A.1.5 | Development of ATLAS-3000 (Stefan Karsch)
Ferenc Krausz, Stefan Karsch
T. W. Hänsch, S. Karsch, F. Krausz, Z. Major, F. Pfeiffer, T. Udem
Other Project Leaders:
K. Achterhold, M.C. Amann, A. Apolonskiy, E. Fill, V. Pervak, N. Picqué