Therefore, we develop laser technologies which we unite in the « Salle Noire » : a laser producing a thousand pulses per second, each of which contains barely more than a single light wave oscillation cycle. In technical terms, this is a laser with a central wavelength of 720 nm (optical cycle is 2.6 fs long) and a minimal pulse duration of 3.5 fs, with a stable carrier-envelope phase and a repetition rate of 1 kHz. Its peak power of a terawatt (10¹² W) and its extremely high temporal contrast make it a worldwide unique laser of its kind.

This laser performance lets us create –in a finely controlled fashion— extreme conditions in plasmas, uniting gigantic forces that accelerate electrons quasi-instantaneously to relativistic velocities. We are particularly interested in dense plasmas created at the surface of solid targets, which behave as relativistic oscillating mirrors in such a way as to temporally compress the oscillations of the reflected light.

This temporal compression adds to the laser light new frequencies in the extreme-ultraviolet (XUV) range, and does so in the form of attosecond flashes. These flashes are of great interest for observing the extremely fast movement of electrons in atoms, molecules or solids, during a chemical reaction or a transition between quantum states.

Another perspective is opened when the attosecond pulses carry a large part of generating laser energy, thus further boosting the peak power. As moreover XUV light can be focused to much smaller sizes than visible light, it may thus become possible to reach new record light intensities and enter a regime where photons interact among each other, or even with the vacuum. The research done within the PCO group contributes to explore also this domain, which bears potential for major new discoveries.