We study electromagnetically-induced transparency (EIT) of a probe field in a Dopplerbroadened five-level K-type atomic system driven by three strong laser (coupling) fields. Effect of wave-vector mismatch occurring when the coupling field frequency is higher than that of the probe field frequency ($\lambda_c < \lambda_p$) are considered. Under the influence of the coherent coupling fields, the steady-state linear susceptibility of the probe laser shows that the system can have single, double or triple EIT windows depending on the amplitude and detuning of the coupling fields.

We study the intensity–intensity correlations of the radiation emitted on probe transition in a three level cascade electromagnetically-induced transparency (EIT) scheme. Further, we show that by applying even a very weak incoherent pump, the nature of the emitted radiation can be switched from classical to non-classicalwithout significantly affecting the probe transparency