The coherently pumped laser: The simplest system for lasers without inversion

Xihua Yang

The transient properties of electromagnetically induced transparency (EIT) with different pump laser energies in a Λ-type three-level system are studied by solving the time-dependent matrix equation. The time evolution of the probe laser absorption, the population of the three levels and the coherent term ρ 23 are analyzed. It is shown that transient amplification without inversion can be realized with high pump laser energy and that transient EIT would reduce and transient amplification without inversion would disappear with the decrease of the pump laser energy. Since the probe absorption depends on the product of Rabi frequency of the pump laser and the coherent term ρ 23, the nonzero damping coherent term ρ 23 results in the transient absorption and amplification without inversion at high pump laser energy, and the decrease of the coherence with the decrease of the pump laser energy leads to the disappearance of the amplification and enhancement of absorption.

Lorenzo M. Narducci, Heide Doss, P. Ru +3 more

Olga A. Kocharovskaya, Francesco Mauri, E. Arimondo

I. R. Senitzky

A three-level system which radiates at both intermediate transition frequencies is considered to be coherently pumped at a frequency near the two-photon resonance frequency. A sharply resonant rise in the second- and third-level population is found for slight detuning of the pump from two-photon resonance. Population inversion in either transition is shown to be possible, depending on the pertinent parameters. This effect furnishes a novel method of population inversion at a frequency higher than the pump frequency. Keywords include: Laser, Laser-type devices, Coherent pumping, Three-level systems, and Quantum electronics.

Ataç İmamoğlu

Vyacheslav I. Yukalov

It is shown that inversion-polarization filaments in laser media arise not only under strong but also under weak pumping. In the system with these filaments a coherent component of radiation appears, while a uniform system could radiate only incoherently. The coherent radiation is sharply anisotropic and is strongest in the direction of the filaments. Notwithstanding the weakness of pumping, in the system with inversion-polariton filaments a super-radiating regime is possible.