Dispersion compensated laser gyro (u)

Abstract

An axial magnetic field applied to the laser gain medium of a laser gyro provides, through the Zeeman Effect, a pair of gain versus frequency profiles relating to respective counter-rotating waves (clockwise and counterclockwise) with their frequencies of maximum gain displaced from one another by an amount which is proportional to the applied magnetic field, and which is substantially equal to the frequency difference caused by an applied directional bias, such that the separation between the frequency of each wave and the frequency of maximum gain of the related gain profile is the same for both waves. This causes the counter-rotating waves to operate on points of equal phase (or index of refraction) on the corresponding dispersion characteristic curve associated with the related gain versus frequency profile. Under these conditions, even if the effective optical length of the gain medium changes in response, for example, to externally induced perturbations of the medium or of the resonant laser frequency, the change is essentially the same for each of the counter-rotating waves, and is thereby substantially cancelled when the wave frequencies are differenced to obtain a gyro output. For example, when cavity length drift causes increases or decreases in both frequencies, thereby causing the waves to intersect different portions of the related dispersion characteristic curve, which are typically not linear or stable, the pair of dispersion characteristics will have similar nonlinearity and instability, and errors resulting therefrom will be substantially cancelled.