We introduce a new technique for measurement of inertial rotations using a semiconductor ring laser, whithin the so-called \\emph{locking band}. The rotation affects the detuning on the optical frequency of the two counterpropagating waves, which are coupled and can be locked by intracavity backscattering making the direct measurement impossible. Here we propose to measure inertial rotation whitin the \\emph{locking band} taking advantage of a phase/amplitude coupling mechanism typical of semiconductor lasers. The dephasing accumulated by the two counterpropagating waves unbalances the fields amplitudes within the locking region. We analytically derive the Responsivity quantifying the two-mode power unbalance versus rotation rate, by means of a two-mode rate equations model. Rotations of the order of $10^{-3}~Hz$ can be measured for $1~mW$ of output power.