The effect of the dipole–dipole interaction in electromagnetically induced transparency in polaritonic band gap materials

Abstract

The effect of the dipole–dipole interaction in electromagnetically induced transparency has been studied in a polaritonic band gap material doped with an ensemble of four-level nano-particles. A probe laser field induces a dipole moment in each particle and a second strong pump field is applied to introduce the interference effect in the system. It is considered that when the concentration of the particles is high the induced dipoles are interacting with each other through the dipole–dipole interaction. The mean field theory is used in the calculation of the susceptibility. Numerical simulations are performed on the absorption coefficient in the polaritonic band gap MgO crystal. This crystal has a 60.5% gap to midgap ratio which is higher than a typical photonic band gap material. It is found that the absorption decreases as the dipole–dipole interaction increases. The resonance peaks are found in the absorption spectrum due to the dipole–dipole interactions and the polaritonic band structure.