CC BY
9LMI-I-2
Comparative study of the electron photoemission from dielectrics, semiconductors, and metals induced by femtosecond laser pulses
G. Duchateau1, N. Fedorov2, B. Chimier1, H. Jouin3, P. Martin3 1CELIA- Universite de Bordeaux, IFCIA, Talence, France 2CELIA- Universite de Bordeaux, golf, Talence, France 3CELIA- Universite de Bordeaux, xuv, Talence, France
The interaction of femtosecond laser pulses with materials is a topic of great interest since this interaction is only partially understood and applications are numerous including material laser processing. Therefore there is a need for further studies of this interaction to improve our knowledge and provide routes for applications. For that purpose, we have studied the electron photoemission from various materials induced by 25-femtosecond laser pulses at 800 nm with intensities below the damage threshold. Conventional dielectrics (SiO2, AhO3, etc), semiconductors (Si, Ge, etc) and metals (Au, Pt, etc) are studied.
The experimental observations, i.e. the electron energy distribution depending on the material and the laser intensity, are analyzed within the framework of the state-of-the-art model of the electron dynamics in solids induced by femtosecond laser pulses. That includes the photo-ionization, the impact ionization, free electron heating by single and multiple photon absorption through intra- and inter-band processes, and electron relaxation through electron-electron and electron-phonon collisions.
Despite various shapes of the electron energy distribution depending on the material class, all observed behaviors can be explained within this model framework. It turns out that the present interaction exhibit an universal behavior in the sense where the electron dynamics is driven by the same processes whatever the material kind. Depending on the bandgap value, the photo-ionization rate evolves, providing different timescale for the laser heating of free electrons. This simple consideration allows to account for the various shapes of electron energy distributions. A corollary conclusion is that the information on the detailed electronic band structure of materials is lost during the interaction.
