The group is researching four-wave mixing in the diamond configuration of Rubidium isotopes. The following figure shows the four-level diamond configuration.
Three lasers of wavelengths 780nm, 795nm, and 1324nm are passed through a heated rubidium cell. This light interacts with the rubidium vapor in a four-wave mixing process that results in light of wavelength 1367nm being emited by the rubidium vapor. The light generated by the FWM process must satisfy phase matching conditions such that theta_3 = theta_1 + theta_2. The FWM light is collected by a photodetector for analysis.
F. E. Becerra, R. T. Willis, S. L. Rolston, L. A. Orozco, "Nondegenerate four-wave mixing in rubidium vapr: The diamond configuration" Physical Review A 78 013834 (2008)
R. T. Willis, F. E. Becerra, L. A. Orozco, and S. L. Rolston, "Four-Wave Mixing in the Diamond Configuration in an Atomic Vapor" October 29, 2008