Lasing without inversion via a self-pulsing instability

The author demonstrate that lasing without inversion can be achieved through a self-pulsing instability. This is shown for the resonant coherently driven three-level media proposed by Kocharovskaya, Mandel and Radeonychev (1992) as inversionless amplifiers of a monochromatic field. A usual instability giving rise to CW lasing is also found. Both instabilities are mutually exclusive, since they are primarily determined by opposite signs of the population difference between the two levels coupled by the driving field. The general necessary conditions for inversionless lasing are given and it is found that the two instabilities require a good quality cavity and are produced in a limited range of driving field intensity.