Comparison of frequency conversion processes in rubidium vapor

Exploiting nonlinear optical processes in a Rb vapor, we describe the generation of optical fields at 420 nm, 1.32 µm, and 1.37 µm.  Laser beams at 780 nm and 776 nm, collinear and circularly polarized, enter a heated Rb vapor cell.  Rubidium atoms are excited to the 5D_5/2 state, with blue light at 420 nm generated by four-wave mixing through the 6P_3/2 → 5S_1/2 states, while infrared beams at 1.37 µm and 1.32 µm are generated by cascading decays through the 6S_1/2 → 5P_3/2  and 6S_1/2 → 5P_1/2 states, respectively.  While the collimated blue light emission from four-wave mixing has been studied in detail, the mechanisms responsible for generating the infrared beams are less understood.  We will present our results for the conditions that give rise to infrared beam generation by two-photon excitation in rubidium vapor.