The interaction of femtosecond and nanosecond laser pulses with the surface of glass

The interaction of femtosecond and nanosecond laser pulses with the surface of glass was compared. The glass was placed inside a vacuum chamber. The laser pulses were focused on the glass surface. The morphology of irradiated glass surfaces and of the materials ejected from the surfaces was examined by scanning electron and optical microscopy. During femtosecond laser irradiation, molten material was ejected from the interaction zone on the glass surface. Nanosecond laser pulses (15 mJ/pulse) induced cracks on the surface of glass, whereas the laser with an energy of 8 mJ/pulse removed a thin layer from the surface through the sputtering process. In the former case, pieces of glass were ejected from the interaction zone, whereas spherical fine powder was produced in the latter case. The femtosecond laser can significantly localize the damage zone. Interference fringes similar to liquid waves were generated on the surface. This indicates that the glass was melted locally by the femtosecond laser irradiation. Shock waves generated by the nanosecond laser (15 mJ/pulse) caused cracks in the glass. The femtosecond laser has advantages over the nanosecond laser due to the creation of a smaller and more precise hole with lower pulse energy and/or a lower repetition rate. (C) 2002 Elsevier Science B.V. All rights reserved.