Diffraction-biased unstable ring resonators with possible applications in laser gyroscopes

The performance of laser gyroscopes is seriously limited at present by the lock-in phenomenon that occurs between the counter-propagating waves at low rotation rates or low values of the beat frequency between the two waves. To minimize or eliminate this lock-in phenomenon, different techniques such as mechanical dither and Faraday cell nonreciprocal-phase elements have been proposed and studied. Here a new idea is presented, which shows how nonreciprocal propagation and a zero-rotation-rate frequency offset can be obtained by a "diffraction-bias" technique employing differential spatial filtering in a negative-branch unstable ring resonator.