2 November 2000 Multiscale mapping technique for the simultaneous estimation of absorption and partial scattering of optical coatings
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The control and measure of losses phenomena is a crucial point for high quality thin film optical components. The knowledge of the statistical and spatial distributions of optical absorption and scattering can give precious information about the structure, the size, the origin and the event frequency of the defects which may play an important role in laser damage for example. The non uniformity of losses, the existence of local defects have led us to perform simultaneous absorptance and scattering mappings. Today, an uplifted set up and original protocols are capable of providing simultaneous mappings of absorption and partial scattering for optical coating s with different spatial resolutions. A micronic spatial resolution is reached, studies and controlled using contrast in absorption targets specially designed for that check by Ion implantation in bulk fused silica substrates. The detectivity threshold is brought down to 0.1 ppm for absorption and 0.01 ppm for partial scattering mapping. The spatial windows investigated can range between micronic area for the study micro of defects as well as centimetric areas in order to check the uniformity of losses. Furthermore, we have developed different processes and numerical tools in the aim to accurately evaluate and study specific parameters: simulation of measurement processes, statistical values of both absorptance and partial scattering over the desired area, tracking down of local defects and estimation of its density, measurement of losses level inside these defects and outside thanks to a mapping zoom technique.
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Alexandre Gatto, Mireille Commandre, "Multiscale mapping technique for the simultaneous estimation of absorption and partial scattering of optical coatings", Proc. SPIE 4099, Optical Metrology Roadmap for the Semiconductor, Optical, and Data Storage Industries, (2 November 2000); doi: 10.1117/12.405808; https://doi.org/10.1117/12.405808

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