Wave-vector mismatch effects in electromagnetically induced transparency inY-type systems

Abstract

We study electromagnetically induced transparency (EIT) of a probe field in a four-level Y-type atomic system driven by two strong laser (coupling) fields. Both homogeneously (radiative) and Doppler broadened systems are considered. The effect of residual Doppler broadening on EIT is demonstrated for various wave-vector mismatches occurring when the frequency of coupling fields is equal (${k}_{c}$ $=$ ${k}_{p}$), higher (${k}_{c}>{k}_{p}$), or lesser (${k}_{c}<{k}_{p}$) than that of the probe field frequency. Contrary to usual belief it is found that for the ${k}_{c}>{k}_{p}$ wave-vector mismatch case, the probe absorption profile displays very wide and almost complete single or double EIT windows whose width, depth, and location depend upon the wave-vector mismatch, Rabi frequencies, and atom field detuning of the coupling fields. Analytical results are also obtained to explain these interesting features.