The development of ultrafast lasers is booming in the international scientific community. We can produce the shortest pulses ever in a laboratory (femtosecond timescale, 1 fs = 10-15 seconds). Such laser beams can be seen as a small pancake of particles (photons) with thickness in the order of the micrometer (10-6 m). This unique feature opens up broad prospects in many areas of basic and applied science.
In particular it provides an unique opportunity to study the matter in unexplored regimes. One striking example is the ability to zoom in down to a timescale corresponding to the elementary displacements of the matter in biology, chemistry, molecular physics, atomic physics, solid state physics, and reveal the fastest dynamics of electrons, atoms and molecules. Another example is to take advantage of these short pulse duration to produce high intensity laser systems while keeping compactness of the infrastructure [Intensity = energy / (spot area x beam diameter)]. The laser intensities at which a target can be irradiated become such that the matter is placed under very high excited states. Laser propagation, production of plasmas and the generation of secondary sources of ultrashort radiation beams covering a spectral range from THz to gamma or energetic particles (electrons, protons, neutrons, ions) are ones of the multiple research topics addressed by the researchers.
The more energetic the ultrafast laser beam is, the less compact becomes the instrument and the lower is the repetition rate. The size of these systems ranges from the simple table to entire buildings several hundred m2. LOA develops and uses laser systems with repetition rates of 0.1 Hz, 10 Hz and 1 kHz delivering a few mJ energy (10-3 joules) to several tens of Joules at wavelengths in the visible and near infra-red spectral range.
The principle of intense femtosecond lasers is based on the technique of chirped pulse amplification. Spectral dispersive systems such as gratings, are used to temporally stretch a laser pulse that can be amplified without damaging the optical elements lying inside the laser chain. It is then temporally recompressed using a conjugated system before being focused onto a target.
There are multiple challenges in the field of laser development. On one side, the race to reach the highest power is pursued with the development of 10 PW lasers (ILE national project, in which the LOA is a pillar of the program). In 2010, lasers producing up to 1 PW with typical pulse durations of 100 fs and energies of 10 J have started to be available for users. On the other hand, much more compact systems are designed and developed. They are less energetic, but with higher repetition rate (up to kHz) with unique beam properties: phase stabilization, duration of a few optical cycles (few fs), time and space shaping, etc...
With its tradition of Laser research, LOA is participating actively in this international effort in close partnership with the worldwide leading laser centers and industrial companies. It allows the implementation of sustainable facilities fully dedicated to users of laser-matter interaction in the laboratory, the design of novel laser systems, and the development of new strategies to overcome the existing bottlenecks in this scientific field.
Part of the amplification module in the intense femtosecond laser system before temporal compression of the beam.
At LOA, the LHP group develops power amplifiers for the 10 PW ILE-laser project and participates to the construction of the LUIRE PW laser system. It also works on time stretching techniques, on novel schemes to produce wide spectral band amplification, and on high average power diode pumping.
The SELF group operates several laser systems at LOA, is responsible for the construction of the LUIRE PW laser for the ILE project, and develops laser diagnostics (measuring time, contrast, spatial profile) at the forefront laser technology.
The PCO group is developing a mJ kHz laser stabilized in phase and works on the optimization of laser temporal profiles (contrast) from nonlinear optics.
The ILM Group develops innovative techniques for ultrashort beam characterization unsig laser
The LOA most powerful LOA laser system is called "Yellow Room", Salle jaune. Experiments on laser-matter interaction with femtosecond powers of 70 TW at a repetition rate of 10 Hz and pulse duration of 30 fs can be undertaken.