Laser gain without inversion

Marlan O. Scully, Michael Fleischhauer

Ataç İmamoğlu, Kenneth L. Campman, Hans‐Werner Schmidt +2 more

We propose a new class of intersubband lasers and amplifiers that achieve net gain without population inversion. The laser scheme is based on a unipolar semiconductor double quantum- well structure where gain occurs at a transition between conduction band subbands. In order to achieve net gain without inversion, we utilize Fano-type interferences. The semiconductor laser scheme that we are considering is analogous to the atomic lambda system that has been extensively analyzed in the context of electromagnetically induced transparency and lasing without inversion. A coherent coupling field however, is not required in the present scheme. The electronic coherence necessary for Fano-type interferences is established by resonant tunneling. For nonlinear optics applications, the asymmetry of the structure allows for (chi) (2) processes and therefore higher conversion efficiency or parametric gain.

Joseph H. Simmons, Kelly S. Potter

Peter B. Sellin, Geoffrey A. Wilson, Krishna K. Meduri +1 more

We experimentally study the production of laser gain (phase-insensitive optical amplification) with and without atomic population inversion in a doubly driven three-level system in atomic barium. The external fields are found to create inversionless gain and to enhance gain available in the presence of inversion. Laser oscillation based on enhanced gain is observed. In analysis of the driven system, we identify an irreversible multiphoton process that is intrinsically supportive of gain in the absence of population inversion. \textcopyright{} 1996 The American Physical Society.

Lei Su

A new way for obtaining laser gain is put forward, whieh does not require to have population inversion between energy levels. The conditions ior laser gain and the coofficient of gain are given.

Ataç İmamoğlu