Control of the emission spectrum of a ring laser by magnetic-field-induced phase anisotropy of the active medium

An analysis is made of the anisotropic properties of an active medium subjected to a magnetic field. The dispersion dependence of the gain dichroism is obtained. The possibility of selection and tuning of the emission frequency of a ring laser is studied, together with the possibility of separating the frequencies of the opposite waves by an amount equal to half the mode spacing. It is shown that the gain dichroism reduces somewhat the efficiency of control of the emission spectrum. The results of an experimental investigation are reported and they show that the wave competition helps considerably to narrow the emission spectrum and to separate the frequency. It is found that selection of the longitudinal modes of a ring laser increases the output power by about 4–8%. The experimental results indicate that the emission frequency can be tuned by altering the magnetic field. Separation of the frequencies of the opposite waves by circular phase anisotropy of the active medium occurs in a wide range of the laser parameters. The error characteristics of such a gyro laser are little affected by the magnetic field instability and the errors are slightly greater than the resonator length instability.