Spatial dispersion of two-photon absorption

Е. С. Воропай, A. M. Sarzhevskii, P. A. Torpachev

B. A. Veklenko

Tatiana N. Smirnova, Eugene A. Tikhonov

Hiroshi Sekiya, Seikyo Tsunekawa, Kiyoshi Nishikawa +1 more

Samuel B. Alves, Hugo L. D. de S. Cavalcante, Gilson F. de Oliveira +4 more

We study the propagation of speckle patterns in a tunable nonlinear medium. Starting from a spatial pattern of photons with a normal distribution (speckle field), we characterize the evolution of the radiation to either subthermal or superthermal distributions and demonstrate the control of this evolution through a single parameter. Our experimental control of the local degree of coherence of the output photons is well described by numerical simulations that consider both dispersive and absorptive nonlinear effects. Particularly, we analyze the role of the nonlinear absorption that either enhances or competes with the dispersive effects in the evolution of speckle fields. In some realizations, an asymptotic power law is observed in the photon spatial distribution.

Harry Friedmann, A. D. Wilson‐Gordon

When a two-level system interacts resonantly with a saturating pump laser, the absorption profile of a probe wave in the Rabi sidebands resembles two separate dispersion profiles. At sufficiently high probe intensity this effect is accompanied by a dispersive profile in the pump-wave absorption, considered as a function of the probe-wave frequency, and also by a dip in the population of the upper state of the two-level system. The relative stabilization of the ground state is interpreted in terms of two-laser-photon processes where absorption of a pump (probe) photon is followed by stimulated emission of a probe (pump) photon. The dispersive absorption profile is attributed to the competition between three- and four-photon scattering processes.