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Using finite difference time domain (FDTD) method, we numerically investigate one-dimensional photonic crystals (1D PCs) with structure, where and stand for different dielectric materials, and the graded-index (GRIN) material. The transmission properties of the multilayer structure have been studied, and the results show that a tunable narrow band-pass filter (BPF) can be obtained by changing gradient coefficients of the GRIN defect layer. For an increasing incident angle, although the transmittance becomes smaller, positions of the resonant peak remain the same, which can act as the angle-insensitive filter. [ABSTRACT FROM AUTHOR]

The transmission properties of a periodic structure consisting of alternating metal layers and air layers are studied by numeric methods. The metal layers are the epsilon-negative (ENG) materials. The interaction of the evanescent waves in metal layers and propagation waves in air layers forms some special transmission bands. Given proper structure parameters, one transmission frequency only allows one incident direction in the low frequency range. This structure can simultaneously achieve frequency filtering and direction filtering. [ABSTRACT FROM AUTHOR]

We calculate the omnidirectional dispersion spectrum for one-dimensional (1D) photonic crystals (PCs) inserting multiple photonic quantum-wells (PQWs) with the use of the plane-wave expansion method in combination with a supercell technique. We find that the localized defect modes significantly depend on the number of the PQWs and the configuration. This may provide a new way to engineer the dispersions of the composite PCs to meet the requirements of optical or microwave devices. [ABSTRACT FROM AUTHOR]

We investigate the evolution of the band gap in one-dimensional (1D) photonic crystals (PC) with the gradual modifications of structural configurations from photonic quantum wells to PC heterostructures. The transmissive spectra are calculated with the use of scattering matrix method. We find that the transmissive spectra and confined states strongly depend on the structural configurations of samples. [ABSTRACT FROM AUTHOR]