High-Efficiency Backward Four-Wave Mixing by Quantum Interference
Zi-Yu Liu1*, Jian-Ting Xiao1, Jia-Kang Lin1, Jun-Jie Wu1, Chin-Yao Cheng1, Yong-Fan Chen1
1Physics, National Cheng Kung University, Tainan, Taiwan
* Presenter:Zi-Yu Liu, email:liuziyu159753@gmail.com
Electromagnetically-induced-transparency-based four-wave mixing (FWM) in a resonant four-level double-Λ system has a maximum conversion efficiency (CE) of 25% due to spontaneous emission. Herein, we demonstrate that spontaneous emission can be considerably suppressed by arranging the applied laser beams in a backward configuration. With the backward double-Λ FWM scheme, we observe a CE of 76% in cold rubidium atoms with an optical depth (OD) of 52. To the best of our knowledge, this is the first observation of a CE exceeding the conversion limit in resonant FWM processes. Furthermore, we present a theoretical model that includes both the phase-mismatch effect and two-photon detuning in the backward double-Λ FWM system. According to the theoretical model, the present scheme can achieve 96% CE using a medium with a large OD of 200 under ideal conditions. Such an efficient frequency conversion scheme has potential applications in optical quantum information technology.

Keywords: Electromagnetically induced transparency, four wave mixing