Electromagnetically induced transparency inside the laser cavity: Switch between first-order and second-order phase transitions

We investigate the effect of electromagnetically induced transparency (EIT) inside a laser cavity. By changing the intensity of an external drive field, we can control the absorption to the laser field. A semiclassical analysis shows that the system undergoes switch between first-order and second-order phase transitions. Around the tricritical point there could be a second-order phase transition followed by a first-order phase transition.