Abstract: Laser etching of a substrate in a liquid is accomplished by laser induced sonic cavitation at the substrate surface. The preferred substrate is laser energy absorbing and has a finite melting temperature. The preferred liquid is an organic or inorganic inert liquid which does not chemically react with the substrate at room temperature. The laser is preferably a copper vapor laser but a chopped beam cw argon ion laser or a YAG laser adjusted to a low power output sufficient to avoid the formation of a recast layer can also be used. The laser parameters are adjusted for causing the growth and collapse of bubbles at the substrate surface. The laser etching has particular application in the fabrication of rails in magnetic head sliders and dicing of Al.sub.2 O.sub.3 --TiC, TiC, SiC, Si/SiO.sub.2, and laser energy absorbing metal and metal oxides.

Abstract: An optical process monitor primarily for use in laser wire bonding detects the reflectivity change of the wire being bonded in order to provide feedback control of the high power laser used for bonding the wire to a pad. A low power laser beam which is co-linear or combined with the high power laser beam is conducted to the bond site and reflected from the wire during the bonding cycle. The change in reflectivity of the wire during the bonding cycle is detected from the reflected low power laser beam. A signal commensurate with the detected change of reflectivity is used to control the power or duration of the high power laser during bonding.