Product Code: PIC2008_M101
Fundamental Issues Concerning Material Removal by Laser Irradiation of Insulating Materials (Invited Paper)
Tom Dickinson, Washington State University; Pullman WA USA
Presented at PICALO 2008
Laser materials interactions underlie a multitude of applications ranging from surface modification and structure formation, machining and cutting, and the formation of atom/molecule/ion sources for thin film growth (pulsed laser deposition). For several years we have been investigating the laser-induced emission mechanisms from materials at fluences below the threshold for optical breakdown in transparent wide bandgap materials. Under these conditions, very gentle, single atomic layer manipulation of surfaces can often be achieved. In the case of wide bandgap materials which are nominally transparent at the laser wavelengths used, we have shown that for ns pulses the interactions are mediated by defects, including defects associated with impurities and deformation. A much clearer and more complete picture of these mechanisms has evolved by more careful characterization and identifying the consequences of defects produced by laser exposure itself. In this talk, we present one important set of studies exploring the interaction of 157 nm light (F2 Excimer laser) with materials such as fused silica and PTFE (Teflon) to explain previous observations by Hermann et al. of superior laser etching of these materials at this wavelength. We also examine 248 nm light (KrF Excimer laser) interacting with alkali halides where we present a novel mechanism for energetic negative ion emission. The accompanying modification of the alkali halide surface provides strong evidence of the role of point defects in this and other emission processes.
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