The controls by optical mean of coatings deposited on optical components are generally made with flat witnesses. When
the components are spherical or aspherical, like lenses or mirrors, the spectral response may vary because of the
nonuniformity of thickness that is really linked to the deposition process. For large radius of curvature, control can be
achieved even with classical spectrophotometers. However, control becomes more and more difficult when the radius of
curvature decreases or when the optical device has a complex shape. Thus special devices are needed to perform this
kind of measurement. ZEISS and CEA Le Ripault use spectral reflection as a mean of measurement, which enables to
investigate optical coatings on curved parts. Two different devices have been implemented and used to measure the same
antireflective coating deposited on an aspheric lens. In this work, we show the obtained results and we compare these
results to theoretical simulation.
Non destructive detection, localization and characterization of
nanocenters today remains a challenge for investigation of
laser-induced damage in optical materials. In this study we
propose an attempt to reach this aim via optical techniques, and
extract size and complex index of nanocenters. The procedure is
described and results are given for SiO2 thin film samples. All conclusions are discussed in regard to assumptions.
Laser damage in optical components is caused mainly by the presence of sub-micronic defects, inherent to the manufacturing process (metal or dielectric inclusions, fractures, bubbles). An improvement of the laser damage threshold requires an analysis of damage process and an identification of the laser damage precursors. However, the assumed nanometer size of such precursors makes their identification difficult by the usual optical methods.
In this paper, we present a method to obtain the size and complex index of laser damage precursors in thin films or substrates. This method is based on the knowledge of three parameters accessible to measurements, which are the precursor density, the laser damage threshold and the precursor absorption. Density and threshold are
extracted from the fit of laser damage probability curves with the use of a statistic model and absorption is obtained with photothermal measurements. From these measurements, an electromagnetic and thermal model permits to obtain an estimation of both complex index and size of the laser damage precursors. The different experimental and theoretical tools are described in this paper : laser damage testing apparatus, photothermal bench, stochastic model for the interpretation of laser damage probability curves, electromagnetic and thermal model. An application example is given : we present our first results in silica thins films where sub-micronic laser damage initiators at 1064nm have been highlighted and identified with our method.
Optical interference coatings usually offer large possibilities for the spectral control of specular reflected or transmitted light. In this aim, multilayer structures are calculated and realized according to each specific application. These kinds of components are deposited over plane substrates, or on substrates with large curvature radius. In this paper we show how multilayer components can also be deposited on micro spheres to reach other applications connected with the spectral control of light scattering.