Stimulated four-wave mixing in the cascade-type atomic system of a warm Cs atomic ensemble.

We investigate stimulated four-wave mixing (FWM) in the 6S-6P-8S open transition of a warm Cs atomic ensemble. Despite the absence of the two-photon cycling transition, we measure high-contrast FWM signals in the 6P-8S transition between the upper excited states according to the frequency detuning and powers of the coupling and driving lasers. The FWM light generation in the upper excited states is interpreted as the FWM phenomena induced by the driving laser of the 6S-6P transition from the cascade-type two-photon coherent atomic ensemble with the coupling and pump lasers. We believe that this work can contribute to the development of hybrid photonic quantum networks between photonic quantum states generated from different atomic systems.