Neutral density filters by co-evaporated Ag and SiO(2) films for near ir radiation.

Optical properties of Ag and SiO(2) co-evaporated films were studied in the visible and near ir regions, and a novel neutral density filter for near ir radiation has been proposed. The films, which contain 56-vol.% Ag, exhibit almost wavelength-independent optical transmittance in the longer than 1-microm wavelength region. Neutral density filters, which have desired optical transmittance, can be obtained by controlling the coevaporated film thickness.