RING-LASER TESTS OF FUNDAMENTAL PHYSICS AND GEOPHYSICS

HeNe ring-laser gyros are standard sensors in inertial guidance; minor reflectances now reach 99.9999%. Present research instruments have an area of similar to 1 m(2), a passive quality factor of greater than o r equal to 10(11), and a resolution of the frequency difference of cou nter-rotating optical beams approaching microhertz. In the Sagnac effe ct, this difference is proportional to the angular velocity. Present r esolution is limited by thermal drifts in frequency pulling, itself re flecting mirror backscatter. The capability of ring lasers for measure ments of geodesic interest, including seismometry and earth tides, and for detection of other sources of nonreciprocal refractive indices, i ncluding axions and CP violation, are discussed. In standard polarizat ion geometries the observable is necessarily rime-reversal odd. Scalin g rules for dimensions, finesse etc summarizing past progress and sugg esting future potential are given.