Positive scale factor correction in the laser gyro

Unlike what was expected, a measurement of the scale factor in the laser gyro as a function of rotation showed it to increase with decreasing rate. At low rates the scale factor peaked and then rapidly dropped to zero at the lock-in threshold. The height of the maximum was found to increase and the width to decrease with operation of the laser closer to lasing threshold. The height varied between 0.003 and 0.3 percent of the nominal scale factor and the half-width varied between 5 and 45 deg/s. A theoretical description of the results was obtained in the asymptotic limit of rates high compared to the lock-in threshold. The shape of the scale factor curve was found to be Lorentzian with a width proportional to the excess gain. The sign of the scale factor correction was found to be due to the phasing of the backscattering, which is the source of the lock-in. This phasing was found to be consistent with the observed 180-deg phasing between the ac components of each beam when the laser is unlocked.