PHASE DYNAMICS IN A SINGLE-MODE CLASS-B LASER

We study the phase dynamics of the electric field in the four-level mo del for the CO2 laser with modulated losses. We show that in the tempo ral evolution of the laser phase there are no phase jumps and phase pl ateaus are almost inexistent. The laser phase on the average increases or decreases according to the sign of the detuning. The onset of ines tabilities as the detuning changes is discussed. We find two propertie s of the laser phase which are invariant with respect to the detuning Delta and the reference frequency Omega and as well on the initial con ditions and the choice of the Poincare section. These properties show that periodic modulation of the losses induces an effective shift in t he frequency of the laser field. Qualitatively similar results are obt ained for the laser phase in the two-level model.