Determination of the Photon Lifetime for DFB Lasers

The photon lifetime of the distributed feedback (DFB) laser is obtained through the relations between cavity photon flux and power associated with the electric fields. The solution of the coupled wave equations provides the propagation parameters and the amplitude gain coefficients for which numerical and approximate solutions are obtained. Using the photon lifetime the threshold condition of the DFB laser within a fixed mirror cavity is determined. The evaluation of both Fabry-Peacuterot and DFB modes is shown by the calculation, using two different photon lifetimes, of all modal concentrations, with the Fermi energy as the independent variable. The current density is also evaluated using the Fermi energy and threshold current is identified as the value when the Fermi energy clamps