We investigated effects of spatially separated laser fields on amplitudes and widths of electromagnetically induced transparency in M-type atomic system. We have shown narrowing of the electromagnetically induced transmission resonance and therefore enhancement of medium non-linearities that can be explained by diffusion-induced Ramsey narrowing. Depending on the polarization of two laser beams, narrow probe Hanle transmission resonance changes its sign in respect of the profile obtained when the pump laser beam is off.
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