Fast characterization of metal films for fiber attenuators

We propose a new procedure for evaluating the complex refractive index of a metal film, based on transmission measurements at different incidence angles. The method is simpler and faster than standard ellipsometry and performs the accuracy required for the design of fiber-optic attenuators for telecommunications. As an example, we report on a device showing a constant attenuation on the 1200-1600-nm wavelength range.