Ring laser gyroscope

Abstract

A laser gyroscope is described having a ring resonator adapted to support a plurality of resonant transverse electric and magnetic field modes TEM.sub.qmn, wherein the longitudinal mode index q is a sequentially different integer for each mode and the transverse mode indices m and n are constant. The gain medium bandwidth is sufficient to simultaneously support at least two adjacent modes, such as TEM.sub.qmn and TEM.sub.(q+1)mn modes. Each mode is split into a set of four components having distinct frequencies, arranged in orthogonally polarized pairs, typically counter-propagating right-handed and left-handed circularly polarized. At least six components can resonate, arranged in three pairs of alternating polarization, two of the pairs from a first mode, for example TEM.sub.qmn, and the third pair formed from the first two components from a second mode, for example TEM.sub.(q+1)mn, with the frequency difference between counter-propagating components of such first pair synchronized to the frequency difference between components of such like polarized third pair, thus resulting in a common frequency difference for all similarly polarized pairs. A magnetic field is applied to the gain medium to equalize the frequency dispersion for each component pair. With such arrangement, pathlength control is not required and the mode components are free to drift in frequency as the pathlength changes. The circulating power is increased to reduce the laser gyro noise due to spontaneous emission.