Temporal characteristics of pulses produced by the simultaneous coupling of modes in free-running class-C lasers

The behavior of class-C lasers in the simultaneous oscillation state of three longitudinal modes is investigated. The general features of these lasers are described by three coupled variables of the cavity electric field, the atomic population inversion, and the dipole moment of atoms. These variables are related to each other by the usual Maxwell–Bloch equations of motion. We solve these equations to derive the amplification gains of the central and adjacent modes and to determine the contribution amount of these modes in the pulses produced by the mode-locking process. The results indicate that the power of pulses is directly boosted by increasing the laser pumping rate and reducing the mean loss rate of the cavity adjacent modes. Finally, the amplitude and phase of all cavity electric field components are calculated and their consistent with the energy conservation law is illustrated.