Functional photonic superstructures: Coherent formation of active-passive photonic band gap heterostructures and photonic subbands

We propose coherently generated photonic heterostructures using a functional photonic superstructure. In the absence of a laser field (control field), such a structure exhibits a conventional passive (off-resonant) photonic band gap. When a region(s) 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 region) and an active (illuminated region) 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.