Phase matching alters spatial multiphoton processes in dense atomic ensembles

Abstract

Multiphoton processes in dense atomic vapors such as four-wave mixing or coherent blue light generation are typically viewed from single-atom perspective. Here we study the surprisingly important effect of phase matching near two-photon resonances that arises due to spatial extent of the atomic medium within which the multiphoton process occurs. The non-unit refractive index of the atomic vapor may inhibit generation of light in nonlinear processes, significantly shift the efficiency maxima in frequencies and redirect emitted beam. We present these effects on an example of four-wave mixing in dense rubidium vapors in a double-ladder configuration. By deriving a simple theory that takes into account essential spatial properties of the process, we give precise predictions and confirm their validity in the experiment. The model allows us to improve on the geometry of the experiment and engineer more efficient four-wave mixing.

12 pages, 6 figures

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Cited by in corpus (5)

• Wavevector multiplexed quantum memory via spatially-resolved single-photon detection
• Four-wave mixing in a non-degenerate four-level diamond configuration in the hyperfine Paschen-Back regime
• Quantum optics of spin waves through ac Stark modulation
• Comparison of collimated blue light generation in ${}^{85}$Rb atoms via the D${}_1$ and D${}_2$ lines
• Spatially-resolved control of fictitious magnetic fields in a cold atomic ensemble