Scatter analysis is an effective method for the characterization of thin film components. The new highly sensitive table top system ALBATROSS-TT (3D-Arrangement for Laser Based Transmittance, Reflectance and Optical Scatter Measurement-Table Top) has been developed at the Fraunhofer Institute in Jena to meet the specific requirements for close-to-process applications. Extremely high sensitivity with a noise equivalent angle resolved scatter level of 2×10(-8) sr(-1), full three-dimensional spherical measurement capability, and an instrument size as small as 0.8 m×0.8 m×0.8 m have been achieved. Details of specifications, optical components, and software are presented, including a comparison to our laboratory system. Anisotropy analysis of diamond-turned aluminum substrates as well as substrate and coating characterization are demonstrated as examples of application.
In every advanced optical system, light scattering caused by the imperfections of optical components sooner or later becomes an issue that needs to be addressed. Light scattering can be a critical factor for both the throughput and the imaging quality of optical systems. On a component level, the quantities to describe these effects are the scatter loss or total scattering (TS) and the scattering distribution function or angle-resolved light scattering (ARS). In the last decades, a number of instruments have been developed worldwide for the measurement of TS and ARS. However, numerous pitfalls have to be avoided to obtain objective, reliable, and reproducible measurement results. This is, in particular, true for low scatter levels of high-end optical components. Standard procedures that have to be both concise and easy to implement are thus of crucial importance for the optics community. This paper tries to give an overview on existing standards as well as an outlook on new standards that are still being developed. Special emphasis is put on ISO standards jointly developed, reviewed, and revised by the international experts in the field
Light scattering measurement and analysis is a powerful tool for the characterization of optical and nonoptical surfaces. To enable a more comprehensive postmeasurement characterization, three visible laser sources were recently implemented in a highly sensitive table-top scatterometer with 3D spherical detection capability. Based on wavelength scaling, the instrument is utilized to characterize thin-film coatings and their substrates with respect to surface roughness, roughness growth, and contamination. Topographic measurement techniques are used to verify the results. The spectral sensitivity to contamination (scatter loss) is demonstrated to be significantly different for single surfaces and interference coatings. In addition, power losses of a highly reflective coating are analyzed.
Light scattering of optical components caused by residual imperfections can be a critical factor for their practical application. In particular, the scattering properties of optical interference coatings are rather complex. Yet, simple theoretical models and comparisons with experimental results provide valuable insight into the main impact factors and mechanisms. The magnitude of scattering and the dominating factors strongly depend on the wavelength of application in connection with the types of coatings used in the corresponding ranges. The paper, therefore, gives an overview of the scattering properties of coatings in different spectral regions including the visible, deep ultraviolet, and extreme ultraviolet and discusses strong in-band variations of the scattering characteristics that have been neglected so far
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