Transient four-wave mixing in a transparent two-component medium

We analyze changes in the spatial structure of an object wave under four-wave mixing in a transparent two-component medium in schemes with opposing and concurrent pump waves. It is shown that in the spatial spectrum of the object wave there is a dip, whose position is determined by the propagation direction of the second pump wave. Angular rotation and frequency shift of the pump waves lead to a decrease in the conversion efficiency of high spatial frequencies. The bandwidth of the spatial frequencies cut out by the four-wave radiation converter decreases monotonically over time, whereas the bandwidth of the most efficiently converted spatial frequencies increases.