Inversionless lasing with self-generated driving field

We propose and study resonant ladder schemes of inversionless lasing on a fast-decaying transition when the population inversion is not possible or Very difficult to achieve. The driving field on a neighboring, slowly decaying transition is not imposed externally, but is self generated in the same active medium. Inversionless lasing in such schemes avoids the problem of driving-field absorption and leads to considerable reduction in the required pumping rate. Applications of such schemes include inversionless ultraviolet and soft x-ray lasing in gas lasers and inversionless generation of coherent mid/far-infrared emission on intersubband (interlevel) transitions in multiple quantum-well or quantum-dot laser diodes.