Technological advancement of large ring lasers

• Applicants: Professor Dr. Heiner Igel; Jan Kodet, Ph.D.; Professor Dr. Simon Stellmer
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Geodesy, Photogrammetry, Remote Sensing, Geoinformatics, Cartography ; Geophysics
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553176123

Ring laser gyroscopes are highly sensitive inertial optical interferometers, exploiting the Sagnac effect on two counter-propagating laser beams in a ring cavity enclosing an area. Today, this technology has matured to routinely obtain the precession and nutation motion of the rotational axis of Earth, which moves by as little as 50 arc seconds per year: ring laser are excellent sensors to observe geophysical phenomena of the system Earth. Apart from variations in the global Earth rotation that influence the rotational velocity or the orientation of Earth in space, a ring laser also senses local seismic ground motion, the rotational component of the microseismic background and the earthquake-induced toroidal eigenmodes of Earth. Sensitivity and stability of current ring lasers are limited by processes not yet fully understood. This includes the dynamics of the gaseous laser medium, thermal coating noise and birefringence of the mirror coatings, coupling between the counter-propagating laser modes, as well as Rayleigh scattering from the residual gas. This project aims to systematically study and understand these phenomena, and to devise methods to mitigate or correct for these systematic effects. Improved ring lasers will reach the quantum shot noise limit even for extended integration times, and will provide high-quality and worldwide unique data to the other projects within the interdisciplinary RING research unit.

• DFG Programme: Research Units
• Subproject of: FOR 5939: RING: Rotational Motions in Physics, Geophysics, and Geodesy
• Co-Investigator: Professor Dr.-Ing. Ulrich Schreiber