Modulated vortex six-wave mixing

We have experimentally generated a vortex six-wave mixing (SWM) signal via a photonic band gap structure in a hot atomic ensemble. The output SWM carrying orbital angular momentum, transferred from a probe beam, has the interaction with the nonlinear effect in the multilevel atomic system. Our results show that a spatial SWM image can be modulated by the detunings and intensities of the related generating fields. Also, the nonreciprocal feature of the SWM signal is demonstrated. Such characteristics can potentially be used in information processing.