Superradiant Laser: First-Order Phase Transition and Non-stationary   Regime
  We solve the superradiant laser model in two limiting cases. First the stationary low-pumping regime is considered where a first-order phase transition in the semiclassical solution occurs. This discontinuity is smeared out in the quantum regime. Second, we solve the model in the non-stationary regime where we find a temporally periodic solution. For a certain parameter range well separated pulses may occur. 
Christian Wiele, Fritz Haake, Kazimierz Rzazewski