Enhancement of photonic band gap in a disordered quarter-wave dielectric photonic crystal

The enhancement of the photonic band gap in visible region for a disordered one-dimensional dielectric-dielectric photonic crystal (DDPC) is theoretically investigated. The DDPC is made of alternating two high/low-index quarter-wave dielectric layers stacked periodically. A disordered DDPC is modeled by randomly changing the real thicknesses, or, the optical lengths, of the two dielectrics. In a single disorder case, where the disorder only appears in one of the two constituents, it is found the photonic band gap can be preferably enhanced for the disordered high-index layer. In the double disorder stack, in which both the constituent layers are disordered, the photonic band gap can, however, be significantly enlarged. In addition, numerical results illustrate that a flat band gap can be obtained by the use of disorder in the optical length.