Narrowing the locking band in a laser with nonlinear absorption

The use of the competing resonances of ring lasers to eliminate frequency locking which imposes a fundamental limitation on the measurement of very low rotational velocities is investigated. It is shown that the width of the locking band is not a constant property and is determined primarily by the nonlinear coupling of the waves because of their reflection from structural elements of the resonator and by the nonlinear interaction of the traveling waves in the laser medium. Since the terms describing this interaction have different signs in amplifying and absorbing media, the nonlinear wave coupling and also the value of the locking band width decrease substantially at frequencies where the nonlinear absorption is most apparent (i.e., near the central frequency of the absorption line). In this situation, the primary contribution to the width of the locking band is eliminated.