FUNDAMENTAL ISSUES CONCERNING MATERIAL REMOVAL BY LASER IRRADIATION OF INSULATING MATERIALS
Below laser fluences where a plasma is formed (the so-called plasma or plume formation threshold) a number of fundamental phenomena can occur where particles such as atomic and molecular ions, atoms and molecular neutrals, and electrons can be emitted. An understanding of such processes are necessary to develop predictive models for material removal from laser irradiated surfaces—at the foundation of laser etching, machining, and pulsed laser deposition. We have reported on a number of the mechanisms for such emission processes on wide bandgap materials. Here, due to space limitations, we present a summary of our studies on the formation negative alkali ion emission from single crystal KCl during exposure to pulsed 248-nm radiation at fluences well below the threshold for plasma formation. Despite the high electron affinities of the corresponding halogen atoms, negative halogen ions were not detected. Significantly, the positive and negative alkali ion distributions overlap strongly in time and space, consistent with K- formation by the sequential attachment of two electrons to K+. Negative alkali ions are also observed under comparable conditions from LiF, NaCl, and KBr. In each material, the strong overlap between the positive and negative alkali ion distributions, and the lack of detected negative halogen ions, suggest that negative ion formation involves a similar mechanism.
J. Thomas Dickinson
Physics Department, Washington State University, Pullman, WA 99164-2814 USA
国际会议
第三届太平洋国际激光与光学应用会议(PICALO 2008)
北京
英文
652-657
2008-04-16（万方平台首次上网日期，不代表论文的发表时间）