AVERAGE FREQUENCY-SHIFTS IN A CLASS-C LASER

We study the average frequency shift W of the phase of the electric fi eld in a laser described by the extended Lorenz model. We discuss new properties of W for parameter ranges where the motion is periodic or c haotic. These properties are invariant with respect to the laser frequ ency of the reference frame and are robust with respect to the main bi furcation parameters given by the incoherent pump and the atom-cavity detuning.