Abstract: When laser gyro with prisms operates in a specific double longitudinal modes and four frequency oscillation state. it can detect the normal component of the earth’s rotation angular velocity without offset frequency, the locking disappears, and the gyro is at the self-biasing state. A mode state control system of the prism ring laser cavity is designed based on the gas density and the refractive index controlling. On this basis, a self-biasing experimental platform is established. The characteristics of self-biasing are obtained from experiments: the two longitudinal modes oscillate in both sides of gain curve, the oscillation intensity ratio of the strength and weak modes is about 1.4 to 1.0. According to the laser semiclassical Lamb theory, a physical model of laser gyro operating in double longitudinal modes and self-biasing is established to derive that the main factor inducing the self-biasing effect is the frequency repulsion of the weak modes. This analytic study provides a reference for developing a new type of self-biasing laser gyro. Key

Key words: ordnancescienceandtechnology, lasergyro, ringcavity, doublelongitudinalmodeoscillation, self-biasing