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High-energy radiation is known to potentially impact the optical performance of silicon-based sensors adversely. Nevertheless, a proper characterization and quantification of possible spectral response degradation effects due to UV stress is technically challenging. On one hand, typical illumination methods via UV lamps provide a poorly defined energy spectrum. On the other hand, a standardized measurement methodology is also missing. This work provides an approach where well-defined energy spectrum UV stress conditions are guaranteed via a customized optical set up, including a laser driven light source, a monochromator, and a non-solarizing optical fiber. The test methodology proposed here allows performing a controlled UV stress between 200 nm and 400 nm with well-defined energy conditions and offers a quantitative overview of the impact on the optical performance in CMOS-based photodiodes, along a wavelength range from 200 to 1100 nm and 1 nm step. This is of great importance for the characterization and development of new sensors with a high and stable UV spectral response, as well as for implementation of practical applications such as UV light sensing and UV-based sterilization.

We realized metal fluoride coatings with a high packing density and a low extinction coefficient by plasma (ion)-assisted deposition. The densification can be performed by different types of plasma sources, e.g., by a Leybold LION source and a Leybold APSpro, respectively. But the as-deposited coatings show a characteristic absorption behavior, whereas the absorption losses can be reduced in a postdeposition UV treatment step. We show experimental results of the plasma-assisted metal fluorides before and after the UV treatment and present a new model that allows us to describe and calculate the characteristic absorption losses of LaF3, MgF2, and AlF3.

LaF(3) thin films of different thicknesses were deposited on CaF(2) (111) and silicon substrates at a relatively low substrate temperature of 150 degrees C. Optical (transmittance, reflectance, refractive index, and extinction coefficient) and mechanical (morphology and crystalline structure) properties have been investigated and are discussed. It is shown that LaF(3) thin films deposited on CaF(2) (111) substrates are monocrystalline and have a bulklike dense structure. Furthermore, it is presented that low-loss LaF(3) thin films can be deposited not only by boat evaporation but also by electron beam evaporation.

A model of a rugate coating that takes into account production potentialities of the Leybold Syrus Pro 1100 deposition system is presented. An efficient algorithm for the synthesis of rugate coatings is proposed. Numerical results are also presented.