We consider dynamically controllable periodic structures (gratings), resulting from Raman interaction of a weak probe field with a standing-wave pump and a second control laser field in four-level atomic media of $N$ type. The gratings under study are induced due to periodic spatial modulation of the Raman gain in a standing pump field and fundamentally differ from the ones based on electromagnetically induced transparency. We show that spectral and transmission properties of these gratings can be controlled with the help of an additional weak field (control field) by varying its intensity or frequency. Small variations of the control field intensity can change the system from opaque to transparent and vice versa and this structure can operate as an all-optical transistor. Such a structure can also be used as a tunable nonlinear mirror with amplification.

• Received 10 July 2015

DOI:https://doi.org/10.1103/PhysRevA.93.013810