A new application of coherent manipulation of EIT (electromagnetically induced transparency) medium is suggested. A two-dimensional photonic cystal with a triangle lattice of elliptic air cylinders, which are filled with the EIT atomic vapor, in the KAs backgroud material is designed. By manipulating the refractive index of the EIT vapor via the external control field, one can obtain the controllable bandgap structure that is sensitive to the variations of external conditions (e.g. the intensity of the control field). It is shown that a large complete bandgap of about 0.0503ωe in the region of high normalized frequency could be achieved by choosing the specific parameters such as the spontaneous decay rate, dephasing rate, Rabi frequency of control light, atomic number density as well as elliptic geometric parameters.
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