Abstract

I present an analysis of a cascade laser system consisting of an ensemble of incoherently pumped multilevel atoms confined in a doubly resonant cavity. When the cavity is tuned onto resonances with both of the one-photon transitions, steady-stale simultaneous lasing on two cascade transitions may be established from the initial population inversion created by the incoherent pumping. When the cascade lasing is initialized, a two-photon coherence is induced and is built up with the increasing lasing intensities. The generated coherence is reacted back to the system and results in light amplification without inversion on one transition. But on the other transition, the two-photon coherence induces light attenuation. Depending on the ratio of the cavity decay rates for the two cascade lasing fields, the system in the steady state may exhibit simultaneously both lasing without population inversion and lasing with population inversion. That is, one laser field is generated from light amplification by coherence, while the other is generated by stimulated emission from population inversion This is the first model system in which both an inversionless laser and an inversion laser may be realized simultaneously.

© 1994 Optical Society of America