The aim of the present paper is to provide a description of the general aspects regarding the theoretical concept, the structure, the execution and the properties of an interferential filter used in a medical application. The main functional characteristic of this filter is to block the radiation supplied by a He-Ne laser ( = 632,8 nm), allowing to passing only the higher wavelength radiation ( > 650 nm). The most important problem that has

In this paper the results of a study and the found solutions for some interferential filters obtained through Physical Vapor Deposition method on optical support are presented. These filters have a good resistance to an intense optical radiation, as well a high optical efficiency in a large spectral domain (400 - 2000 nm). Both theoretical and experimental aspects will be discussed herein.

An ellipsometric experimental set up of PSA type with an extinction factor E.F.= 10-5, inspired from the Gaertner’s L119 and a powerful BASIC software for the theoretical calculus of the ellipsometric parameters  and , including original practical solutions, were developed. Encouraging results were obtained in applying the simple ellipsometric method of azimuths to determine the optical constants: refractive index n, absorption index k and