Radiation characteristics of a multimode linear Zeeman laser

An experimental study is presented of a 3.39-micron multimode linear He-Ne Zeeman laser in a longitudinal magnetic field. Conditions are achieved in which elliptically polarized longitudinal modes of the laser are locked by the modulation of resonator losses at the frequency of intermode beats; modulation is carried out using a germanium acoustooptic modulator. An analysis of the laser-emission spectrum is presented, and the frequency and polarization characteristics are investigated. Experimental data on locking and free-lasing regimes are compared, and the observed effects are explained. It is shown that the frequency splitting of modes with opposite signs of ellipticity (achieved by the superposition of a longitudinal magnetic field on the active medium) in the regime of longitudinal-mode locking is realized over the whole gain line of the active medium.