Exploiting the giant Kerr nonlinearity associated with electromagnetically induced transparency, an atomic phase grating created with arbitrarily weak fields is proposed. Almost 30% of a probe beam can be diffracted into the first diffraction order.
We proposed a scheme for realizing electromagnetically induced grating via the giant Kerr nonlinearity in a coherently driven four-level system with spontaneously generated coherence. In the presence of spontaneously generated coherence,Kerr nonlinearity could be enhanced with vanishing linear absorption. Thus,with a standingwave coupling field,one could achieve a pure absorption grating,which led the probe field to gather the zero-order direction when the detuning of the coupling field was on resonance. Moreover,we could obtain a pure phase grating,which diffracted a weak probe light into the first-order direction and the second-order direction when the detuning of the coupling field was off resonance.
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.