Metal multi-dielectric mirror coatings for Cherenkov detectors

Application-specific reflective coatings have been developed and are being implemented in LHC experiments currently under construction. The broadband reflective coating consists of an aluminum film combined with one or two pairs of low- and high-index dielectric layers. The layer stacks are designed and optimized using commercial thin film software and verified on small mirror samples. The wavelength of peak reflectivity is tuned to maximize the light yield, taking into account the emission spectrum (e.g., Cherenkov) and the photosensor characteristics. We report about coatings of Mylar foil-based light guides for the Hadronic Forward calorimeter of CMS and spherical mirrors for the RICH2 counter of LHCb.