A new topology optimization algorithm is proposed based on bi-directional evolutionary structural optimization (BESO) method in order to design photonic crystals with maximum band gaps. The optimization process starts from a simple unit cell without band gap, and the photonic crystals are assumed to be periodically composed of two materials with different permittivity. Based on finite element a...

A band diagram is the fundamental for investigation of the electromagnetic properties of periodic structures such as photonic crystals in optics or electromagnetic band gap structures in antenna engineering. In this paper, the two famous computational methods, finite difference frequency domain (FDFD) and finite difference time domain (FDTD) methods are applied for band diagram calculation of 2...

Zinc nitride (Zn3N2) nanowires (NWs) with diameters of 50 to 100 nm and a cubic crystal structure have been grown on 1 nm Au/Al2O3 via the reaction of Zn with NH3 including H2 between 500°C and 600°C. These exhibited an optical band gap of ≈ 3.2 eV, estimated from steady state absorption-transmission spectroscopy. We compared this with the case of ZnO NWs and discussed the surface oxidation of ...

We consider a model of multiband superconductivity, inspired by iron pnictides, in which three bands are connected via repulsive pair-scattering terms. Generically, three distinct superconducting states arise within such a model. Two of them are straightforward generalizations of the two-gap order parameter while the third one corresponds to a time-reversal symmetry-breaking order parameter, al...

Recently, photonic band-gap (PBG) structures are under intense research due to their various applications in optics, microwave, and antenna engineering. Therefore, the accurate modelling of band diagram of frequency-dependent PBG structures is highly needed because the electric properties of all of the materials depend on frequency. In this paper, a new finite-difference frequency-domain (FDFD)...

by means of first principles calculations we show that both rutile and anatase phases of bulk tio2 doped by s, se or pb can display substantial decreasing in the band gap (up to 50%), while doping by zr does not sizably affect the band-gap value. moreover, the absorption edge is shifted (up to 1 ev) to the lower energy range in the case of tio2 doped by s or pb that opens a way to enhancing of ...

The design of one-dimensional photonic crystals and the analysis of their optical properties have been performed using band diagram and forbidden gap map methods. It has been shown that the latter method is more useful for practical applications since i it can be applied for any number of periods and ii it is more suitable for the selection of a filling fraction in a wide range of values using ...