Three-periodic 1D photonic crystals for designing the photonic optical devices operating in the infrared regime.

We investigate theoretically and numerically one-dimensional three-periodic photonic crystals of the structure [(SiO2/TiO2)N(Al2O3/ZrO2)M]K, formed by dielectric oxides SiO2, TiO2, Al2O3, and ZrO2 (N and M are the number of subperiods, and K is the number of superperiods). We study the transmission spectra, energy and power fluxes of TE- and TM-polarized electromagnetic waves for a photonic crystal, characterized by the sharp PBG edges, and narrow and pronounced peaks of defect modes. The angular distance (difference in the incidence angles) between the transmission peaks of different polarizations is shown to be about 1.5°, which is 5 times more than in the ternary photonic crystals. The results can be useful for designing highly efficient optical devices operating in the infrared regime on the side-surface of the photonic crystal, such as polarization-sensitive couplers and angle sensors for optical fiber systems.

Hartman effect for spin waves in exchange regime.

Hartman effect for spin waves tunnelling through a barrier in a thin magnetic film is considered theoretically. The barrier is assumed to be created by a locally increased magnetic anisotropy field. The considerations are focused on a nanoscale system operating in the exchange-dominated regime. We derive the formula for group delay τgr of a spin wave packet and show that τgr saturates with increasing barrier width, which is a signature of the Hartman effect predicted earlier for photonic and electronic systems. In our calculations, we consider the general boundary conditions which take into account different strength of exchange coupling between the barrier and its surrounding. As a system suitable for experimental observation of the Hartman effect we propose a CoFeB layer with perpendicular magnetic anisotropy induced by a MgO overlayer.