A hybrid in situ monitoring strategy for optical coating deposition: Application to the preparation of chirped dielectric mirrors

A new optical monitoring strategy for interference coating deposition has been developed that combines in situ optical broadband transmission spectroscopy with quartz crystal thickness monitoring. We present a short description of the basic monitoring concept, the experimental set-up, and the data elaboration facilities of the developed optical monitoring system, OptiMon. Although it is flexible enough to be implemented into different types of deposition systems, we focus here on the application of our monitoring system for coating preparation with advanced plasma source assisted electron beam evaporation. Chirped mirrors have been prepared using SiO2 and Ta2O5 as low and high index materials, respectively. The layers are characterized by in situ transmission spectroscopy, ex situ transmission and reflection spectroscopy, and white light interferometry to determine the group delay dispersion, GDD. Based on the characterization results, we demonstrate and discuss the relative benefits of the developed monitoring strategy.