Laser etching processes: Towards sub-picosecond X-UV irradiation

Since the first observation of high order harmonic generation (HOHG) in a r are 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 fue l research into the fundamentals of the HOHG process [1], its practical imp lementation 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 o f these ultrashort pulses to initiate photochemical processes on clean or a dsorbate-covered (SF6 or CCl4) silicon surfaces. More recently, femtosecond or even atto-second laser pulses has been evoked as being the best tools t o photo-ablate polymeric materials [2]. VUV studies [3] also demonstrate th at higher photon energies applied on the same kind of matter can decrease d ramatically the threshold fluence for the onset of ablation. We seek to det ermine exactly what happens when both conditions (ultrafast and VUV pulses) are combined during irradiation.