A breakthrough instrument for wide-range wavelength and angle resolved light scattering measurements of high performances optical coatings
Résumé
Due to the diversity and complexity of optical functions they address, optical coatings are widely used in space optics but
the level of both their specifications and performances is now so high that the characterization of their optical properties
requires the development of extreme metrology. In this context we present in this paper the last state-of-the-art instrument
for thin-films characterization. This apparatus is unique by the performances and the levels of detectivity achieved. It
operates spectrally and angularly resolved characterization of Angle Resolved Scattering (ARS) over a wide and continuous
spectral range from 400 nm to 1.7 μm. The spectral resolution is lower than 1 nm, while the angular resolution is lower
than 1° with a precision better than 1%. The lowest levels of scattering measured are close to 10-8 sr-1, near to the limit of
air particles scattering. The large angular range available offers the opportunity to evaluate scattering functions both in the
forward and backward half-spaces. In specific configurations, this same setup records specular properties, achieving again
unreached levels of detection and precision over the same spectral range and with the same resolution. All measurements
have shown great agreement with theoretical designs and numerical predictions, for both scattering and transmittance
records. This instrument is an upgraded version of an apparatus developed in the Scattering group for more than five years
formerly operating in the visible wavelength spectrum and now extended to near-infrared with the same level of
performances.
Domaines
Optique [physics.optics]
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