Precision stabilization of the optical frequency in a large ring laser gyroscope

Pressure-induced fractional changes of 10(-7) in the geometry of a large He -Ne ring laser gyroscope induce backscatter phase changes and thus a fracti onal pulling of the Sagnac frequency of similar to 5 x 10(-3). To counter t his, the optical frequency was stabilized against an iodine-stabilized lase r with a high-finesse Fabry-Perot interferometer and piezoelectric control of the ring perimeter. This scheme, although limited in principle by residu al geometric asymmetry and in practice by low beam powers (10 pW), stabiliz ed the perimeter to 2.4 nm (6 x 10(-10) or 300 kHz for the optical frequenc y) and the Sagnac frequency to 100 parts per million over several days. (C) 1998 Optical Society of America.