Multiphoton-avalanche absorption yields with femtosecond laser pulses in the wavelength range 1300–2200nm

Summary form only given. In the past few decades, 3D direct writing with focused femtosecond laser pulses has emerged as a technique for microfabrication inside transparent dielectrics like fused silica. It has been demonstrated that the control and the confinement of the non-linear interaction can lead to a wide variety of modifications: from a small uniform change of the refractive index to structural modifications opening the way to applications like optical memory encoding, optical waveguide and/or microfluidic channel fabrication [1-3]. The purpose of our study is to extend these 3D fabrication capabilities to semiconductors, a domain that has still not been exploited. We specially concentrate on silicon (Band Gap=1.1 eV) which remains the basis material for microelectronics and telecommunication applications. For comparison, we perform also the experiments on fused silica (Band Gap=9 eV) and various other materials with band gap varying from 1.1 to 13.6 eV.