Abstract

Until recently, the losses in ZnS waveguides have been attributed primarily to scattering at the coating interfaces. Our results, however, show that the total waveguide attenuation is caused by a combination of volume and surface losses. By relating the losses of multiple guided modes to their individual field properties, namely, the field amplitudes at the interfaces and the power-confinement factor, we are able to separate volume and surface contributions to the total waveguide attenuation. If the losses are caused mostly by surface scattering, the higher losses may be attributed to an increase in the rms surface roughness, which can result from larger crystallites. However, initial investigations show that the surface losses, which are approximately 1.5 dB/cm, are independent of the total attenuation, which varies over 3-10 dB/cm. This suggests that the losses in ZnS waveguides may not be dominated by surface roughness. We employ a two-dimensional charge-coupled device camera interfaced with a computer to measure the losses of ZnS waveguides. By using these data, in conjunction with x-ray diffraction measurements of crystallite size and one-dimensional surface profiling, we hope to gain further understanding of the mechanisms that contribute to the losses in ZnS waveguides.

© 1990 Optical Society of America