Amplification and generation without population inversion in two- and three-level atomic media in a strong polyharmonic light field

Abstract

The paper deals with non-linear laser spectroscopy of atoms in strong polyharmonic quasi-resonance laser field. The main goals are a theoretical study of the emission amplification effects in two- and three-level atomic media without population inversion, a calculation of the generation parameters at adjacent transitions in such spectral regions and such media where it is impossible or complicated to create usual lasers, e.g. in the UV and X-ray spectral region. Theoretical calculations show that the amplification effects without inversion in polyharmonic fields are connected with atom emission during transitions between the quasi-energy states into which the usual levels are splitted under the influence of a strong polyharmonic field. There are also transitions between quasi-energy sublevels and usual atomic levels. Hence, generation is possible in the spectral region which does not coincide with the pumping region (e.g., in a three-level system). Some of these conclusions have been already checked experimentally. Supernarrow resonances in the atomic susceptibility spectrum are found out experimentally and calculated theoretically. This is a new type of nonlinear resonances which can be used to stabilize the laser frequency, to receive generation without inversion in twoand three-level media. On the basis of the experiments, it is intended to build new stabilized coherent emission sources in the media without population inversion in the UV spectral region on the atoms of alkali-earth elements.