Multi-wave-mixing-induced nonlinear effects in an electromagnetically induced grating.

We propose a multi-field-coupled atomic model that exhibits controllable $symmetric$ and $asymmetric$ evolution of significantly enhanced diffraction peaks in an opto-atomic grating at far-field regime. Such results are obtained by the linear and nonlinear modulation of the intensities of the diffraction peaks as a result of multi-wave-mixing-induced modification of spatially modulated coherence in a closed four-level atomic system. Novelty of the results lies in predicting super symmetric alignment of the diffraction peaks due to the dominance of the amplitude part of the grating-transfer-function at the condition of exact atom-field resonance, which is unique to the present model. Efficacy of the present scheme is to apply it in producing nonlinear light generated by four-wave-mixing-induced control of spatially modulated coherence effect. The work also finds its importance for its applicability in the field of high-precision atomic lithography.