Abstract

Laser-assisted modification of solid surfaces, e.g. thin film deposition and etching, frequently involves a chemically reacting system whose optical and thermal properties change continuously in time. This leads to a coupling between excitation and reaction which has profound consequences for the cumulative effect of microscopic processes occurring at the surface, whether thermal or photochemical in nature. An understanding of this coupling provides an essential bridge between investigations of discrete mechanistic steps in surface photoreactions and measurements of macroscopic rates of laser etching and deposition. A range of situations have been found to lead to significant interdependence between optical properties and reactivity: formation of waveguides and gratings, chemical enhancement of absorption, coupling of optical properties and temperature, and optical feedback in scanning. Typical examples are presented and discussed. The real-time effects of growth of a reflecting Ni film on an absorbing substrate, of optical interference in the laser thermal oxidation of copper and of grating formation in the photochemical deposition of copper are described in detail.