Enhanced and stimulated two-photon processes in free atoms

Guy Mayer, J. Sevin

Shaul Yatsiv, Mehran Naghizadeh rokni, S. Barak

An enhanced two-photon emission has been observed between the 6S and the 4S levels of potassium. The priming field is the stimulated electronic Raman emission at 2720 cm-1due to scattering of ruby laser radiation from the4P_{3/2}state in potassium. The intense emission at the complementary frequency ω2is close to the 5P → 4S resonance lines. As a result, the coupling coefficient has a resonance character that is favorable for the enhancement. The observed results are compared with a simple analysis. The relation of the enhanced emission with two-quantum absorption, stimulated Raman effect, and parametric four-photon processes is discussed.

Roberto de J. León‐Montiel, Juan P. Torres

We show that the sensitivity and robustness of a label-free optical imaging technique based on stimulated Raman scattering (SRS) can be enhanced by using resonant optical transitions in a Raman adiabatic passage scheme. Our approach is based on the consideration that any enhancement of the flow of energy between two light beams involved in the SRS process is related to an increase in atomic population transfer between the energy levels of interest. One can thus profit from techniques developed in quantum optics to maximize such atomic population transfer for enhancing the sensitivity and robustness of optical imaging techniques.

Zhidang Chen, Helen S. Freedhoff

Nikolai B. Delone, В. П. Крайнов

Li Deng, Chengjie Zhu, E. W. Hagley

We present a semiclassical theoretical framework on light-wave mixing and scattering with single-component quantum gases. We show that these optical processes originating from elementary excitations with dominant collective atomic recoil motion are stimulated Raman or hyper-Raman in nature. In the forward direction the wave-mixing process, which is the most efficient process in normal gases, is strongly reduced by the condensate structure factor even though the Bogoliubov dispersion relation automatically compensates the optical-wave phase mismatch. In the backward direction, however, the free-particle-like condensate structure factor and Bogoliubov dispersion result in highly efficient light-wave mixing and collective atomic recoil motion that are enhanced by a stimulated hyper-Raman gain and a very narrow two-photon motional state resonance.