  We derive the statistics of scattered photons from a $\Lambda$- or
ladder-type three-level emitter (3LE) embedded in a 1D open waveguide. The weak
probe photons in the waveguide are coupled to one of the two allowed
transitions of the 3LE, and the other transition is driven by a control beam.
This system shows electromagnetically induced transparency (EIT) which is
accompanied with the Autler-Townes splitting (ATS) at a strong driving by the
control beam, and some of these effects have been observed recently. We show
that the nature of second-order coherence of the transmitted probe photons near
two-photon resonance changes from bunching to antibunching to constant as
strength of the control beam is ramped up from zero to a higher value where the
ATS appears.
