Active control and sensitivity of the "G-Pisa" gyrolaser

G-Pisa is an experiment dealing with a high-sensitivity laser gyroscope operating in a square cavity of side length of the order of 1 m. We report on the active stabilization of the gyrolaser optical frequency which is mainly driven by the environmental thermal fluctuations. Stabilized operations make it possible to perform rotation measurements without interruptions due to mode jumps. The long-term stability is dominated by backscattering effects which introduce a slow and deep frequency modulation on the Sagnac interference signal. We measured a sensitivity limit, mainly given by environmental and anthropic noise, at the level of 2.10(-9) (rad/s)/root Hz. Applications of this gyrolaser as a high-sensitive tilt-meter in the large-frame interferometers for gravitational waves detection are discussed.