Electromagnetically induced blazed grating at low light levels

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.