Thin film filters with variable transmittance for spectrometry

Abstract

Optical interference filters are widely used in optics for various applications. Depending on the optical system specifications, either edge filters or band-pass filters are required. In this last category, special attention is paid to narrow band transmission filters which use is greatly expanding in both telecommunication and spectrometry. In this work, narrow band transmission filters are proposed which performance is varied along the filter surface. These variable filters allow the construction of compact spectrometers that are useful in all applications where both weight and dimensions are required to be very low. Transmission filters operating in a wide wavelength range, visible and shortwave near infrared, are described. Their peak transmittance is linearly moved in one direction along the component surface, within a total length smaller than 10 mm. The filter structure is composed of a thin-film multilayer stack containing both metal and dielectric materials.