Laser rate equations

Summary

The laser rate equations are a system of ordinary differential equations for a laser. The unknowns are the population inversion of the gain medium and the number of photons in the cavity. They model pumping, spontaneous decay, stimulated emission and cavity losses as rates of gain and loss. They predict the lasing threshold, the output power above threshold, and relaxation oscillations after the laser is switched on. They are a simplification of the Maxwell–Bloch equations when the polarization of the medium decays fast.