Theory of nonreciprocal effects in a ring laser subjected to a transverse magnetic field

Equations are derived for the description of steady-state multimode operation of a ring laser in an arbitrarily oriented magnetic field in the case when the resonator anisotropy is much stronger than the anisotropy of the active medium induced by the magnetic field. The transverse component of the magnetic field gives rise to nonreciprocal effects of two types: one of them is a polarization nonreciprocal effect which is due to a difference between the coefficients describing the nonlinear interaction of waves in an active medium and which depends on the ellipticity e of the radiation as ε(1–ε ²)/(1+ε ²)²; the other is a dispersion nonreciprocal effect which is due to an asymmetry of the frequencies of the opposite waves in the ring laser relative to the gain curve and which, in contrast to the former effect, is observed in the case of linear and circular polarizations of the radiation. Computer calculations are reported of the dependences of these effects on the intensity and direction of the magnetic field in the case of active medium and resonator parameters of the kind usually encountered in experiments.