Design and operation of a very large ring laser gyroscope

The design and initial operation of a vertical square He-Ne ring laser GO w ith a perimeter of 14 m is discussed. This builds on earlier demonstrations of the feasibility of large ring lasers (perimeter similar to 4 m) for sin gle-mode gyroscope operation and with lesser pulling than navigation gyrosc opes. With servoing of the rf excitation to yield single-mode operation, G0 gave a quality factor 1 x 10(12) and a Sagnac line with a frequency of 287 .8 +/- 1.0 Hz induced by Earth rotation Omega(E). This has confirmed some v ital questions over the feasibility of very large gyroscopes for geodetic m easurements at the level of 10(-9) Omega(E). (C) 1999 Optical Society of Am erica.