Beyond inversionless gain to a demonstration of field-enhanced lasing

Summary form only given. We experimentally demonstrate field-enhanced lasing, i.e., lasing made possible through an excitation-field-mediated boost in the gain normally realizable on a weakly inverted transition. The excitation field responsible for the boost in gain, the "helper" field couples the lasing transition to another transition in a cascade-type three-level atomic system. The gain boosting operative in our driven three-level-atom experiments derives from the same essential physics that gives rise to the "inversionless" gain that has recently attracted so much attention. In terms of achieving laser operation in new regimes, gain boosting may play much the same role as inversionless gain.