Controllable nonlinear optical processes in six-wave mixing and fluorescence channels

For the first time, we experimentally study the phase control of the coexisting dressed probe signal, six-wave mixing and fluorescence signals in a five-level K-type atomic system by adjusting the angle between the probe signal and certain coupling beams. Such phase controlling results in a switch between bright and dark states. In addition, by using different hyperfine levels of the K-type atomic system as the ground state, the magnitude of the dressing effect is manipulated. The mechanisms of the three types of nonlinear processes are investigated by changing the frequency detuning and powers of the coupling laser beams. In addition, we study the interference and competition among the involved beams in nonlinear optical processes. Such controllable nonlinear processes could have potential applications in optical communication and quantum information processing.