Determination of volume and surface contributionsto the total attenuation in ZnS waveguides.

We relate the modal waveguide attenuation of polycrystalline ZnS films to their mode field properties, namely the field amplitudes at the interfaces and the power confinement factor, to show that the totalwaveguide attenuation is caused by a combination of volume and surface effects. Our results show that the surface losses for the TE(0) mode, which are approximately 1.5 dB/cm, are independent of the total attenuation, which varies from 6 to 40 dB/cm. This suggests that the losses of the lower-order modes are dominated by volume effects such as scattering from crystallite boundaries and absorption.