Gravitational-wave detection through the use of competing resonances of ring lasers

Nonlinear competing resonances in the output of ring lasers might be used to detect ultrasmall changes in optical path length. Because of the competition between the oppositely directed waves, these resonances are considerably sharper than those in linear lasers. An absolute sensitivity of 5 x 10 to the -7th A has been achieved in the detection of periodic perturbations of the position of one of the resonator mirrors with a baseline of 0.85 m in a He-Ne/CH4 ring laser.