Study of the dynamical behaviour of the polarization of a quasi- isotropic laser in the earth magnetic field

High-gain quasi-isotropic lasers are shown to be very sensitive probes of the Earth magnetic field. The rate of rotation of the polarization is shown to exhibit an Adler-type evolution with the azimuth of the laser propagation axis, with a locking region depending on the controlled loss-anisotropies introduced in the cavity. The evolution of this rotation rate with the excitation and the detuning is also investigated. It is also shown that the sensitivity of the laser to the Earth magnetic field increases when extra losses are introduced in the cavity, leading to a sensitivity of a few hundredths of Gauss. In every case, a good agreement is observed between experiments and theory.