We use a coupled-wave theory analysis to describe an atomic phase grating based on the giant Kerr nonlinearity of an atomic medium under electromagnetically induced transparency. An analytical expression is found for the diffraction efficiency of the grating. Efficiencies greater than 70% are predicted for incidence at the Bragg angle.
The electromagnetically induced grating is investigated in a four-level double V-type quantum system. It is shown that the electromagnetically induced transparency established by the cross-Kerr nonlinear effect can be canceled by the four-wave mixing in a closed-loop atomic system and that the diffraction of the probe beam depends on the relative phase of the applied fields and can be controlled by this parameter. We find that an additional nonlinear contribution is established in the medium response by applying a microwave field to the system and that the electromagnetically induced absorption grating turns to the electromagnetically induced phase grating. This contribution leads to 100% diffraction efficiency in the first-order direction, so we can say that the proposed grating could be considered as a special candidate for the optical networking and communication.
We propose a scheme for inducing a blazed transmission grating in a four-level, N-type atomic medium under electromagnetically induced transparency (EIT). The blazed grating relies on the giant Kerr nonlinearity that the atomic medium exhibits under EIT. The grating is created using an intensity mask in one of the driving optical fields and only weak fields with intensities below saturation level are involved. Diffraction efficiencies of a resonant probe beam close to 100 are predicted.
A new scheme to investigate an electromagnetically induced grating in an N-type configuration in the presence of a strong-standing coupling field, additional coherent fields, and microwave driven fields is presented. By considering the coherent population trapping (CPT) condition in a four-level microwave driven N-type atomic system, a novel nonlinear optical storage is obtained via linear absorption vanishing and giant Kerr nonlinearity during light propagation. It is revealed that nonlinear properties in this atomic medium are maximum in the CPT condition, and these nonlinear properties could be affected and modulated by means of a microwave driven field. In this condition high-phase modulated diffraction efficiency is attained. The diffraction pattern is sensitive to variables of the phase and amplitude of microwave field. Consequently one can control the efficiency of different orders of grating more conveniently. The first-order diffraction efficiency of the grating, about 45%, can be obtained by choosing optimum values for the phase and amplitude of the microwave field. It is shown that the phase and modulation grating could be controlled effectively by atomic field-radiation parameters such as the interaction length L of atomic samples and applied field detunings. It has been noted that a novel fast communication device could be obtained at the zero absorption point and on the superluminal light level.