U. Schreiber, M. Schneider, G. E. Stedman, W. Schlueter
Characteristics of a Ring Laser for Geodesy
 
                   ABSTRACT
 
 
Large Ring lasers are not yet used for geophysical applications. C-II is a
prototype for such a device and has a square optical path with side 1 m.
One difference with the earlier C-I laser testbed - and similarity to an
aircraft gyro - is its monolithic construction. It is housed 30 m
underground in a New Zealand military bunker. The measured ringdown time of 0.20
ms corresponds to a quality factor 6e+11 and a finesse 9.4e+4.
For the observed exit beam power of 10 pW, this gives an angular rotation
sensitivity 4e-9 rad/s/sqrt(Hz). C-II performance limits
therefore rival those of Sagnac matter-wave gyroscopes (2e-8
rad/s/sqrt(Hz), Gustavson et. al., Phys. Rev. Lett. 78, 2046-9 (1997)).
This also corresponds to a quantum noise line width of 220 microhertz,
consistent with that observed (172 microhertz) in the direct spectrum
and with the coefficient of inverse time in the Allan variance plot.
 
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In Proceedings of the 13th Working Meeting on European VLBI for Geodesy
and Astrometry, Viechtach, 1999
 
Keywords: ring laser, gyroscopes, Sagnac effect, earth rotation