Ring-laser tests of fundamental physics and geophysics

TLDR

HeNe ring‑laser gyros, with mirror reflectances up to 99.9999 %, achieve microhertz‑level resolution of counter‑rotating beam frequency differences, enabling precise Sagnac‑based angular velocity measurements, though thermal drift and backscatter limit current performance. The study discusses the use of ring lasers for geodesic measurements such as seismometry and earth tides, and for detecting non‑reciprocal refractive index sources like axions and CP violation. In standard polarization geometries the observable is necessarily time‑reversal odd. Scaling rules for dimensions, finesse, etc., summarizing past progress and suggesting future potential are given.

Abstract

HeNe ring-laser gyros are standard sensors in inertial guidance; mirror reflectances now reach 99.9999%. Present research instruments have an area of , a passive quality factor of , and a resolution of the frequency difference of counter-rotating optical beams approaching microhertz. In the Sagnac effect, this difference is proportional to the angular velocity. Present resolution is limited by thermal drifts in frequency pulling, itself reflecting mirror backscatter. The capability of ring lasers for measurements of geodesic interest, including seismometry and earth tides, and for detection of other sources of non-reciprocal refractive indices, including axions and CP violation, are discussed. In standard polarization geometries the observable is necessarily time-reversal odd. Scaling rules for dimensions, finesse etc summarizing past progress and suggesting future potential are given.