Passive ring resonator method for sensitive inertial rotation measurements in geophysics and relativity.

As part of a program to develop sensitive laser inertial rotation sensors, we have studied the performance of a passive-resonator technique using a 0.7-m x 0.7-m optical cavity. For an averaging time tau of 10 sec, the random drift was 1.1 x10(-2) deg/h, which was consistent with the shot-noise limit for the present setup. For a longer averaging time the random drift was 5.6 x 10(-3) deg/h (tau = 90 sec), showing a slight departure from the shot-noise limit. The problems encountered in the present apparatus, as well as those that are critical in the development of much larger esonators for geophysics and relativity applications, are discussed.