Coherent Phenomena in Photonic Crystals
  We study the spontaneous emission, the absorption and dispersion properties of a ${\bf \Lambda}$-type atom where one transition interacts near resonantly with a double-band photonic crystal. Assuming an isotropic dispersion relation near the band edges, we show that two distinct coherent phenomena can occur. First, the spontaneous emission spectrum of the adjacent free space transition obtains `dark lines' (zeroes in the spectrum). Second, the atom can become transparent to a probe laser field coupling to the adjacent free space transition. 
D. G. Angelakis, E. Paspalakis and P. L. Knight