O EDP Sciences, Les Ulis Laser etching processes: Towards sub-picosecond X-UV irradiation

Abstract. Since the first observation of high order harmonic generation (HOHG) in a rare gas jet, the creation of ultrashort laser pulses in the extreme UV (XUV) has been a field of continuous development. The increasing accessibility of femtosecond lasers and chirped pulsed amplifiers (CPA) has helped to fuel research into the fundamentals of the HOHG process [l], its practical implementation and tentative uses of such a source in spectroscopy. One of our particular interests in the use of this facility is to study the ability of these ultrashort pulses to initiate photochemical processes on clean or adsorbate-covered (SF, or CCI,) silicon surfaces. More recently, femtosecond or even atto-second laser pulses has been evoked as being the best tools to photo-ablate polymeric materials [2]. V W studies [3] also demonstrate that higher photon energies applied on the same kind of matter can decrease dramatically the threshold fluence for the onset of ablation. We seek to determine exactly what happens when both conditions (ultrafast and VUV pulses) are combined during irradiation. 1