A laser gyro with optimized resonator geometry

Experiments on laser gyros with adjustable beam path geometry yield a strong dependency between the lock-in threshold and the distribution of the backscatter sources. Based on a simple vector formalism, a theory is presented which describes the lock-in threshold as a function of the beam path geometry. In accordance with the experimental results, the theory is a helpful tool to minimize the lock-in threshold by an optimization of the resonator geometry. The theory also offers an explanation of the fact that the quality of laser gyros often differs, even between gyros of the same production series, under the same operating conditions and with mirrors of comparable quality.