Dielectric micrometric machining with ultrashort laser pulses

• Grant number: 09/07912-0
• Support Opportunities: Regular Research Grants
• Start date: September 01, 2009
• End date: August 31, 2011
• Field of knowledge: Engineering - Mechanical Engineering - Manufacturing Processes
• Principal Investigator: Wagner de Rossi
• Grantee: Wagner de Rossi
• Host Institution: Instituto de Pesquisas Energéticas e Nucleares (IPEN). Secretaria de Desenvolvimento Econômico (São Paulo - Estado). São Paulo , SP, Brazil

Abstract

The development of ultrashort laser pulses, with temporal pulsewidth in the range of dozens of femtoseconds (10-14s), has allowed the production of electric fields with intensities never thought before. The intensity of such focused laser beam can easily exceed 5 x 1020 W.m-2, which corresponds to nearly the electric-field strength that binds the valence electrons in the atoms - of the order of 109 V.m-1. This causes physical phenomena never observed before and has been explored in many fields of physics and engineering. Particularly it is possible the machining of controlled structures with hundreds of nanometers in any kind of material. As the timescale for electron heating is smaller than the electron-phonon scattering time, it is possible under specific conditions the occurrence of material ejection before heat diffusion to the lattice, eliminating all heating effects outside the focal area. This increase the precision of the machined region allowing the production of "damaged areas" even smaller than the laser wavelength (l » 800 nm).The aim of this work it to use a femtosecond laser beam to study its interaction with some dielectrics and to obtain a correlation between the process parameters and the size of the affected zone as well as its morphology. From this point, projected structures of few microns in size will be machined to be used in specific applications. The cases to be studied are: machining of microchannels in SiOxNy to microfluidics use; drilling of micrometric holes in polymers to production of chemical filters and superficial engineering in alumina to osteointegration improvement in medical implants. In more detail it will be carried out studies concerning the physical mechanism of damage formation in BK7 optical glass, amorphous sapphire and monocrystalline Ti:sapphire laser medium. Here the purpose is double: to find out the conditions that maximizes and the conditions that minimizes the damage threshold in these materials. The first condition is useful to high intensity laser chains where the laser beam would not cause damage to the optical components. The second condition is desirable to an efficient machining in the surface of these materials. (AU)