1 Laser Research
Group coordinator:

MBI Laser research concentrates on the generation of extremely short and/or intense laser pulses with cutting edge parameters. For the MBI as a research institute devoted to short pulse spectroscopy and nonlinear optics the development of novel laser sources is of paramount importance. Laser sources developed in-house offer parameters that are at the scientific state-of-the-art unavailable from commercial lasers In particular, the availability of a very broad spectral range from terahertz radiation up to hard X-rays enables unique experiments. Few cycle pulses, ultra-intense short laser pulses, compact, diode pumped laser sources, ultrafast nonlinear optics for frequency conversion and pulse characterization, and new materials are presently in the centre of our attention.

The generation of extremely short laser pulses with cutting-edge parameters has always attracted significant attention, extending far beyond laser physics. For the MBI as a research institute devoted to short pulse spectroscopy and nonlinear optics, the development of novel sources of ultra-short light pulses is of paramount importance. Laser research at the MBI is strongly interconnected, both among the different research themes within the laser research as well as to direct applications in the other focal areas. Many of these activities are embedded into international collaborations and are made accessible to external users through the application laboratories.

The two key directions of laser research pursued at the MBI are generation and control of ultra-short and few cycle light pulses in a very broad spectral range and amplification of ultra-short pulses to very high intensities up to 1020 W/cm2.

Continuous improvement of temporal resolution

State of the art studies of dynamics in the gas phase, condensed matter and on surfaces demand yet shorter pulses in the whole spectrum from 100 nm up to the THz range. As one approach to meet this challenge, we follow the proven path of continuum compression in hollow gas-filled fibres to pulse durations of less than 5 fs, we aim at further improvement of broadband nonlinear conversion techniques, and we make these pulse sources available for applications in spectroscopy. As an alternative road, we also pursue new strategies for pulse compression such as nonlinear processes in holey fibres and photonic crystals. For pulse compression in the ultra-violet and mid-infrared Raman-active molecular modulation is expected to allow for pulse durations down to a few femtoseconds. For tuneable and efficient generation of sub-100 fs pulses in the wavelength range from 100 to 165 nm, we investigate both experimentally and theoretically, four-wave-mixing in special hollow waveguides and compression of vacuum UV pulses by higher order stimulated Raman scattering. New techniques and elements for control and characterization of sub-20 fs pulses in the whole spectral region will also be investigated.
Research project 1.1

Ultra-high intensities

The objective is the provision of laser parameters relevant for relativistic plasma dynamics, particularly laser-particle acceleration, using compact lasers with single- or multi-Joule pulse energies. This requires peak intensities on the order of 1019 or 1020 W/cm2, and comprehensive control over pulse duration and pulse shape, particularly pulse contrast. The research strategy includes investigation of methods to increase the contrast of the pulse, such as double-CPA, to further reduce the pulse duration below the present < 40 fs (e.g. by negative-positive-CPA), and to increase the peak power of the Ti:sapphire laser to the 100 TW regime. The research is closely linked to infrastructure projects dealing with comprehensive pulse characterization and synchronisation of two high-intensity lasers in the high-field application laboratories.

New materials for efficient generation of ultra-short light pulses

One focus of this topic is the progress of compact diode-pumped femtosecond laser systems. The potential of novel ytterbium and neodymium doped active materials and semiconductor structures are studied in the 1-µm spectral range. In addition we also investigate lasers based on active microstructure fibres. Compared to conventional fibre designs, microstructure fibres have considerably enhanced the possibilities of tailoring linear and nonlinear fibres properties. For mode-locked fibre lasers, dispersion engineering is of particular interest, as it permits intrinsic dispersion compensation or soliton propagation at virtually arbitrary wavelengths.

Design, construction, and characterization of short pulse laser systems with special time structures (burst-mode laser) or controlled temporal and spatial pulse parameters

This is done in close contact with the users of these systems at accelerators and free electron lasers. Present research activities focus on tuneable fs-burst-lasers with high average power using nonlinear optical amplification schemes instead of resonant amplification in an excited laser medium. The main advantages of this scheme are a negligible thermal lensing, a broad amplification bandwidth and a large tunability in wavelength. Future developments will include a better active control of laser pulse parameters by nonlinear and active electro- or acousto-optical techniques and the increase of the average power of such systems.
Research project 1.2