Optically Tunable Photonic Stop Bands in Homogeneous Absorbing Media.

Resonantly absorbing media supporting electromagnetically induced transparency may give rise to
specific periodic patterns where a light probe is found to experience a fully developed photonic band gap
yet with negligible absorption everywhere. In ultracold atomic samples the gap is found to arise from
spatial regions where Autler-Townes splitting and electromagnetically induced transparency alternate with
one another and detailed calculations show that accurate and efficient coherent optical control of the gap
can be accomplished. The remarkable experimental simplicity of the control scheme would ease quantum
nonlinear optics applications.