By: R. Lahoz, L. A. Angurel, M. T. Flores-Arias, G. F. de la Fuente

Instituto de Ciencia de Materiales de Aragón, Unidad Asociada de Óptica y Microoptica GRIN

Laser ablation backwriting has been recently reported useful to induce diverse functionalities in glass. In particular, it has been used to obtain planar waveguides and diffraction gratings which should enable noncomplex and environmentally benevolent miniaturization of elements for integrated optics applications.  The quality of the metal-like coatings achieved on glass surfaces has been improved by the use of excellent beam profile diode-pumped Nd:YAG lasers, and may also help achieve electrically conductive coatings with important applications in the transportation and construction industries.

Intense ns Laser irradiation induces thermal ablation on the surface of a metallic plate positioned behind a window-glass substrate. Part of the ablated material deposits onto the glass surface above it, following the plasma plume generated at the focal spot. Laser backwriting is achieved focussing the laser beam onto the metal and moving it in a direction controlled by a CAD type computer programme. In this manner, any figure that the laser beam projects through the glass medium will be permanently incorporated into the glass substrate surface facing the metal target.

Surface roughness and electrical resistance measurements suggest that the laser emission and working atmosphere (air, Ar) considerably affect the electrical properties and morphology of the resultant coatings.

Work presented at ICALEO 2010 demonstrated that a simple laser ablation variant can be used to obtain metallic coatings on window glass substrates. Coatings with metallic conductivity have been attained under certain irradiating conditions. An increase in scanning speed and in laser repetition rate resulted in larger layer thicknesses. Two ablation regimes that led to a substantial change in thickness (400 to 100 nm) and electrical conductivity (from M Ω/cm to about 10s Ω/cm) were identified.