New concept of the gamma-ray source: coherent stimulated annihilation of relativistic electrons and positrons in a strong laser field

The process of stimulated coherent annihilation of relativistic electron–positron pairs in the strong laser field is examined. It is shown that if the energy of laser photon in the beam (center-of-mass) reference frame exceeds mc2, coherent stimulated generation of γ-ray photons becomes possible. Electron–positron pair in the electromagnetic field can be considered as an inverted two-level quantum system, in which the two-photon transition is allowed with the stimulated emission of one γ-quantum and one photon of the laser mode. In analogy with the effect of self-induced transparency in the conventional nonlinear optics, the nonlinear oscillation regime arises at high laser intensities, in which inversion can be removed in one pass and the π-pulse of coherent γ-ray radiation is generated. Estimates show the scheme proposed is a promising high-brightness source of coherent γ-radiation.