Rate equation model of a coupled-cavity laser

In the present derivation of a rate equation system for a laser consisting of two tandem, coupled cavities, the photon rate equations are derived on the basis of classical electromagnetic theory, while the rate equations for the electrons are written down heuristically in analog with the conventional laser rate equations. Attention is given to the initial numerical evaluation of the coupled cavity laser model, which indicates that the laser tends to oscillate in a single longitudinal mode, unlike a single-cavity laser of comparable length. Although the coupled-cavity laser maintains single-wavelength operation even if the peak of the gain profile shifts over a certain wavelength range, when finally responding to a sufficiently large shift of the gain profile it does so by jumping discontinuously to a new, single, operating wavelength.