A new method for determining thin-film refractive index and thickness using guided optical waves

We have developed a new method for determining thin-film refractive index and thickness. In this technique, a sharply converging laser beam is coupled into the film by a prism. Dark mode lines characteristic of the waveguide structure are observed in reflection independently of absorption or scattering loss in the film. A particularly promising application is the rapid sampling of dielectric films in semiconductor technology.