Passive ring laser gyroscopes to access fast variations in EOPs

Quite generally, the Earth Orientation Parameters (EOPs) as obtained via VLBI and GNSS lack short-term sensitivity on (sub-)diurnal timescales. To access these fast dynamics, large active ring laser gyroscopes have been devised and are currently operated in geodesy and seismology. Here, we propose a novel type of gyroscope, namely passive ring lasers. By placing the gain medium outside of the optical resonator, the passive variant may remove many of the systematic limitations of active gyroscopes, and holds the potential to increase sensitivites by two orders of magnitude. Interfacing the gyroscopes with our optical clock technology will improve long-term stability as well. We will report on preliminary work and on the design and anticipated performance parameters of two demonstrators, as put forward by a recently established European collaboration.