The scientific objectives of LOA are driven by the broad range of applications in fundamental science and applied physics that the interaction between an intense femtosecond laser and the matter can lead to.
The infrared laser beam as well as beams of energetic particles and radiations produced by laser-plasma interaction have unique properties (compactness of infrastructures, extreme short pulse duration, coherence, intensity, small source size) that may play a pioneering role for the development of innovative industrial and societal applications.
We use the very short pulse duration of beams to achieve high temporal resolution in the analysis of the fastest reaction dynamics in matter (electron, atom, molecule, structure). Our goal is to reveal transient states of matter remaining unobservable with more conventional techniques. These timescales are the fraction of a femtosecond (1 fs = 10-15 s) for electrons ( revolution time of an electron for hydrogen: 152 attosecond (1 as = 10-18 seconds) and a few tens of femtoseconds for atoms (typical period of oscillations of optical phonons).
We primarily use the technique of time-resolved spectroscopy for which a first beam triggers a reaction and a second beam (laser, particle or radiation produced by laser) probes at various time delays following the excitation. These temporal resolutions require a perfect synchronization between the different beams. Laser technology allows such type of experiments.
The LOA has made several breakthroughs in this field, including the first demonstration of X-ray diffraction in the femtosecond timescale. We study the dynamics of aggregates and magnetic domains, phonons in strongly correlated materials and supraconductors. The high intensity of these secondary sources can also be used to extend the study of nonlinear physics from the infrared to the XUV and X spectral range.
We take advantage of the micrometer and sub-micrometer source size of X-ray radiation, the smallest ever produced in a laboratory, to develop the technique of phase contrast imaging, or to probe the dense and warm plasmas. The possibility of generating radiation of several tens of keV and hundreds of MeV allows us to probe dense matter like fusion plasmas as well as to excite nuclear transitions. Zeptosecond (1 zs = 10-21 s) pulse duration are foreseen and would provide a direct access for the first time to the dynamics of particles inside the nucleus.
The intense femtosecond laser is used to guide electrical discharges such as lightning. The plasma channel generated by the laser in its wake propagates in the air over long distances and can capture and guide the energy.
High resolution radiography of a capsule of a dense material with a source of gamma radiation produced by intense femtosecond laser interaction with matter. The source size of the source can achieve resolutions as small as a few tens of microns in this spectral range.
The treatment of cancerous tumors using lasers offers the potential to significantly downscale the size and the cost of protontherapy infrastructures. This could lead to high dissemination in hospitals, as compared to more conventional systems based on RF acceleration that require the construction of large infrastructures. A multidisciplinary and national research program supported by OSEO was launched mid-2009 at LOA with both academic and industrial partners to demonstrate this innovative technique.
The coherence and very small source size of these laser-plasma X-ray source are used to develop high resolution imaging for early detection of tumors.
Unlike X-rays, protons can deposit their energy in a localized way inside the tissues, allowing the destruction of certain cancerous tumors without affecting surrounding healthy tissue.
The eye surgery using femtosecond lasers is also extensively studied at LOA. We work on the optimization of corneal transplants by manipulating the laser wavefront. We develop methods to address glaucoma diseases with in-situ optical coherence tomography. Novel techniques of optical imaging of anterior segment tissues are also developed.
The tissue ablation using femtosecond lasers allows the development of very efficient eye surgery techniques. The LOA is mainly working on glaucoma, and on the manipulation of the laser beam to develop new imaging techniques and to optimize the laser-tissue interactions.