We propose coherently generated photonic heterostructures using a functional photonic superstructure. In the absence of a laser field ͑control field͒, such a structure exhibits a conventional passive ͑off-resonant͒ photonic band gap. When a region͑s͒ of such a structure is illuminated by the control field, coherent enhancement of refractive index increases the refractive index perturbations of that region, while electromagnetically induced transparency keeps it lossless. This forms a photonic heterostructure consisting of a passive ͑unilluminated region͒ and an active ͑illuminated region͒ photonic band gap structures. Using such a superstructure, we study a coherently generated photonic quantum well structure wherein two active photonic band gaps sandwich a passive region. We show that, since the active photonic band gaps are roughly twice wider than the passive band gap, they form two photonic barriers around the transparency band located at the longer wavelength side of the passive photonic band gap. This leads to formation of resonant transparency states or photonic subbands, similar to the conduction or valence subbands in electronic quantum well structures. We show that the energies and linewidths of such photonic subbands can be coherently controlled by just adjusting the control field beam.The analogy between photons in spatially periodic dielectric structures and electrons in crystalline semiconductors has led to significant research for fundamental and device applications. These applications include nanodevices, quantum computing, light sources, quantum buffers, etc. 1,2 Significant attempts have been devoted to confine photons in one-, two-, or three-dimensional photonic band gap ͑PBG͒ systems, similar to confinement of electrons in quantum wells, wires, or dots. Construction of a photonic quantum dot via patterning a planar optical microcavity structure has already been reported. 3 Here, by decreasing the lateral size of the structure, the optical modes shift to higher energies. These modes are analogous to sharp discrete states of an electronic quantum dot. 4,5 By bringing two or more photonic quantum dots together, as shown in Ref. 6, one can also form a "photonic molecule." The spectroscopy of such a structure has shown that the energy splitting of the confined photonic modes increases with the decreasing the length of the channel joining the two dots, in close analogy to the emergence of electronic bonding and antibonding modes in diatomic molecules. Photonic quantum wells ͑QWs͒ have also been studied by sandwiching a medium between photonic barriers formed by several layers of semiconductors. The presence of quantized confined states in such structures, similar to those in semiconductor quantum wells, has been investigated. 7,8 In the above cases, the photonic potentials responsible for confining photons were generated by spatial variation of semiconductor materials, either by etching or forming a heterostructure of semiconductor materials with different refractive indices. In this paper, we propo...
