Design and operation of a very large ring laser gyroscope

Abstract
The design and initial operation of a vertical square He–Ne ring laser G0 with a perimeter of 14 m is discussed. This builds on earlier demonstrations of the feasibility of large ring lasers (perimeter ∼4 m) for single-mode gyroscope operation and with lesser pulling than navigation gyroscopes. With servoing of the rf excitation to yield single-mode operation, G0 gave a quality factor 1 × 1012 and a Sagnac line with a frequency of 287.8 ± 1.0 Hz induced by Earth rotation ΩE. This has confirmed some vital questions over the feasibility of very large gyroscopes for geodetic measurements at the level of 10-9 ΩE.