C. Le Blanc

Measurement of the nonlinear refractive index of transparent materials by spectral analysis after nonlinear propagation

A fast and accurate method for the measurement of the nonlinear refractive index of transparent materials is presented. The method is applied to various solids and liquids. The effective femtosecond response time of the optical Kerr effect in benzene and methanol is determined.

Compact and efficient multipass Ti:sapphire system for femtosecond chirped-pulse amplification at the terawatt level

We have developed efficient multipass Ti:sapphire amplifiers for femtosecond chirped-pulse amplification. With only two of these devices we get an amplification factor of 10(8), which corresponds to a peak power of ~0.5 TW after compression. We present a detailed analysis of such a system and its advantages in terms of its high quantum yield (0.3), flexibility, optical quality, and potential for tunability.

Generation of 25-TW, 32-fs pulses at 10 Hz

We have developed a femtosecond laser chain that generates 25-TW pulses of less than 35 fs at 10 Hz with focused intensities higher than 5 x 10(19) W/cm(2) and an average power of 8 W. This system is optimized for a broad transmission bandwidth and includes an aberration-free stretcher compressor.

Gain-narrowing and gain-shifting of ultra-short pulses in Ti: sapphire amplifiers

Abstract We have developed a simple model for chirped-pulse titanium: sapphire amplification that includes gain narrowing and gain shifting effects. We analyse the spectral limitation in ultra-short pulse amplification and compare two different kinds of pre-amplifiers: multi-pass and regenerative amplifiers. We compare the model to multi-pass Ti: sapphire amplifier measurements using different input bandwidths.

Phased-array grating compression for high-energy chirped pulse amplification lasers

The development of phased-array grating compressor is a crucial issue for high-energy, ultra-short pulse petawatt-class lasers. We present a theoretical and experimental analysis of two-grating phasing in a broadband pulse mosaic compressor. The phase defaults induced by misaligned gratings are studied. Monochromatic grating phasing is experimentally achieved with an interferometric technique and pulse compression is demonstrated with a two-phased-array grating system.

Synthetic aperture compression scheme for a multipetawatt high-energy laser.

High-energy petawatt lasers using the chirped-pulse amplification technique require meter-sized gratings to limit the beam fluence on the surface of the grating. An alternative, studied by many groups, is a mosaic grating consisting of smaller, coherently added gratings. We propose what we believe to be a new compression scheme consisting of beam phasing instead of grating mosaic phasing. This synthetic aperture compression scheme allows us to control the beam thanks to a unique segmented mirror equipped with three degrees of freedom. With this configuration, the beam is divided into small subapertures adapted to the classical grating size. After compression, these subapertures are coherently added before the focusing stage. Therefore the alignment processes are simplified.

Generation of 27 fs pulses of 70 kW peak power at 80 MHz repetition rate using a cw self‐pulsing Ti:sapphire laser

We have built a self‐mode‐locked Ti:sapphire cw oscillator delivering up to 2 W of average output power. This oscillator provides 100 fs pulses tunable in the 770–807 nm range. Using a fiber‐prism compressor at the cavity output, the pulses have been compressed down to 27 fs at 785 nm, while keeping 200 mW average power.

Extreme Light Infrastructure: Architecture and major challenges

Extreme Light Infrastructure (ELI), the first research facility hosting an exawatt class laser will be built with a joint international effort and form an integrated infrastructure comprised at last three branches: Attosecond Science (in Szeged, Hungary) designed to make temporal investigation at the attosecond scale of electron dynamics in atoms, molecules, plasmas and solids. High Field Science will be mainly focused on producing ultra intense and ultra short sources of electons, protons and ions, coherent and high energetic X rays (in Prague, Czech Republic) as well as laserbased nuclear physics (in Magurele, Romania). The location of the fourth pillar devoted to Extreme Field Science, which will explore laser-matter interaction up to the non linear QED limit including the investigation of vacuum structure and pair creation, will be decided after 2012. The research activities will be based on an incremental development of the light sources starting from the current high intensity lasers (APOLLON, GEMINI, Vulcan and PFS) as prototypes to achieve unprecedented peak power performance, from tens of petawatt up to a fraction of exawatt (1018 W). This last step will depend on the laser technology development in the above three sites as well as in current high intensity laser facilities.

Changes in the geometry during the laser-induced multiple ionization and fragmentation

The average nuclear geometry of molecules during the laser-induced multielectronic ionization and multifragmentation is probed by Coulomb explosion into multicharged atomic fragments. An evolution from the initial bent structure to a linear configuration is observed as the number of removed electrons increases from 3 to 11 in the laser intensity range. This observation shows that the multiple ionization does not follow a simple sequential pattern from the less bound to the more tightly bound electrons of the molecule.

Multi-pass amplification of sub-50 fs pulses up to the 4 TW level

Abstract We describe the design and operation of a 2-stage multi-pass Ti:sapphire amplifier laser system, which is optimised for a broad transmission bandwidth and incorporates a novel reflective spherical mirror pulse-stretcher. Output energies of 180 mJ after compression, and amplified bandwidths up to 30 nm are observed.