Electromagnetically induced two-dimensional grating assisted by incoherent pump

- Two-dimensional grating is coherently induced in four-level atoms.
- Phase and gain-phase gratings are obtained assisted by incoherent pump.
- The diffraction power is improved due to the enhanced refraction modulation.
- The gratings can be utilized as multi-channel all-optical splitter and router.

We propose a scheme for realizing electromagnetically induced two-dimensional grating in a double-Λ system driven simultaneously by a coherent field and an incoherent pump field. In such an atomic configuration, the absorption is suppressed owing to the incoherent pumping process and the probe can be even amplified, while the refractivity is mainly attributed to the dynamically induced coherence. With the help of a standing-wave pattern coherent field, we obtain periodically modulated refractive index without or with gain, and therefore phase grating or gain-phase grating which diffracts a probe light into high-order direction efficiently can be formed in the medium via appropriate manipulation of the system parameters. The diffraction efficiency attainable by the present gratings can be controlled by tuning the coherent field intensity or the interaction length. Hence, the two-dimensional grating can be utilized as all-optical splitter or router in optical networking and communication.