Abstract

Excitation of leaky waveguide modes by internal reflection is used to measure the thickness of multilayer films (1-4 μm), their ordinary and extraordinary indices, and the changes in them to better than 0.0001 resolution. The films are made by PCVD of a-Si:H/a-Si₃N₄:H and a-SiO₂:H/a- Si₃N₄:H multilayers on the planar base of a crystalline silicon hemicylinder. Near-infrared linearly polarized light (1.3 and 1.53 μm) is focused on the base of the hemicyclinder. The angular distribution of the reflection intensity minima (dark lines) corresponds to the leaky waveguide mode resonance conditions. Applying an electric field between a metallic electrode (deposited on the film) and the hemicylinder allows the electrorefraction in the film to be measured from the shift in the resonance angles. Both TE and TM polarization modes are excited, and the electrorefraction in both polarizations is thus observed. A model which takes into account the form birefringence of the film, absorption in both film and electrode, and electroabsorption effects is used to extract the thickness, refractive index, and electrorefraction information from the resonance angles.

© 1987 Optical Society of America