Abstract

The laser frequency ω₁ in coherently driven lasers is desired to be larger than the frequency ω_d of the drive laser (frequency up-conversion). In the simplest case of homogeneously broadened, resonant, closed three-level systems, a necessary condition for inversionless lasing is that the spontaneous population decay rate of the driving transition must be larger than that of the lasing transition. This condition is not easily found to occur in real systems allowing frequency up-conversion because these decay rates scale with the cube of the transition frequency. It is also well known that two-photon Raman processes are responsible for gain in the V-scheme. therefore it is neither necessary not convenient to work on resonance. In fact, we have recently shown that when both drive and laser fields are detuned but approach the two-photon resonance condition it is possible to relax the above condition between spontaneous population decay rates [1]. This therefore opens new possibilities to obtain inversionless lasing from Doppler broadened systems.

© 1998 IEEE