Low-light-level four-wave mixing by quantum interference

Chiu, C-K, Chen Y-H, Chen Y-C, Yu IA, Chen Y-C, Chen Y-F.  2014.  Low-light-level four-wave mixing by quantum interference. Phys. Rev. A. 89:5.


We observed electromagnetically induced transparency-based four-wave mixing (FWM) in the pulsed regime at low light levels. The FWM conversion efficiency of 3.8(9)% was observed in a four-level system of cold 87Rb atoms using a driving laser pulse with a peak intensity of ≈80 μW/cm2, corresponding to an energy of ≈60 photons per atomic cross section. Comparison between the experimental data and the theoretical predictions proposed by Harris and Hau [Phys. Rev. Lett. 82, 4611 (1999)] showed good agreement. Additionally, a high conversion efficiency of 46(2)% was demonstrated when applying this scheme using a driving laser intensity of ≈1.8 mW/cm2. According to our theoretical predictions, this FWM scheme can achieve a conversion efficiency of nearly 100% when using a dense medium with an optical depth of 500.