Controllable four-wave mixing in an atom–optical cavity coupling system with a second-order nonlinear crystal

The four-wave mixing (FWM) effect has been systematically studied in an atom–optical cavity coupling system with a second-order nonlinear crystal (SOC), which is formed by coupling an optical cavity with a two-level atom and a SOC. In this research, it is found that the FWM effect largely depends on the SOC, because the SOC can promote a two-photon absorption process. Therefore, a tunable FWM signal can be obtained in this coupling system by controlling the SOC. Moreover, the results also show that the cavity decay rate plays an important role in controlling the FWM signal. By optimizing the cavity decay rate and the SOC, a strong FWM signal can be generated. In addition, by adjusting the cavity–pump detuning, conversion between a single-peak FWM signal and two-peak FWM signal can be easily realized.