Spectrum of vertical-cavity surface-emitting lasers: linewidth properties and non-degeneracy of relaxation oscillation frequencies

We give an analysis of the spectrum around the laser line of vertical-cavity surface-emitting lasers. We show that they contain sidebands which are not symmetrically located on each side of the laser frequency and that this asymmetry corresponds to a non-degeneracy of relaxation oscillations of the carriers. A model which explains this non-degeneracy is introduced.