We propose an asymmetric distribution of a hexagonal lattice for achieving near-zero group velocity with negative delay. This study reports the effect continuous geometric perturbation on photonic band diagram and consequently its impact phase velocity, effective refractive index. provide promising method modifying to obtain exotic dispersion diagram. With this broadband spanning from E L band,...

Metamaterials offer unprecedented flexibility for manipulating the optical properties of matter, including the ability to access negative index1–4, ultrahigh index5 and chiral optical properties6–8. Recently, metamaterials with near-zero refractive index have attracted much attention9–13. Light inside such materials experiences no spatial phase change and extremely large phase velocity, propert...

We have designed and built a soft-x-ray interferometer to test the possibility of a direct measurement of the refractive index (i.e., the real part of the complex index) of materials in the soft-x-ray range. The interferometer is based on the Fresnel bimirror setup. It works near the zero path difference and requires only little spatial coherence. Plane mirrors at grazing incidence are the only...

original article   to determine the association between ocular biometric components and near work in bank employees.this study was conducted as an analytical cross-sectional study. a group of bank employees and a control group were randomly selected. after applying the inclusion criteria, all selected subjects had a set of examinations including refraction, uncorrected and corrected visual acui...

Abstract Materials with near-zero refractive index have attracted much attention over the past decade due to fascinating phenomena they enabled, such as energy squeezing in thin waveguides, engineering of wavefronts, and “photonic doping”. These materials are not directly available nature, but can be realized periodic artificial structures. Among materials, double-zero-index a special type both...