Noise Level of a Ring Laser Gyroscope in the Femto-Rad/s Range.

Absolute angular rotation rate measurements with sensitivity better than prad/s would be beneficial for fundamental science investigations. In this regard, large frame Earth based ring laser gyroscopes are top instrumentation as far as bandwidth, long-term operation, and sensitivity are concerned. Here, we demonstrate that the GINGERINO active-ring laser upper limiting noise is close to 2×10^{-15}  rad/s for ∼2×10^{5}  s of integration time, as estimated by the Allan deviation evaluated in a differential measurement scheme.