Nanofabricated photonic materials offer opportunities for crafting the propagation and dispersion of light in matter. We demonstrate an experimental realization of a two-dimensional negative-index material in the blue-green region of the visible spectrum, substantiated by direct geometric visualization of negative refraction. Negative indices were achieved with the use of an ultrathin Au-Si3N4-...

In this paper, the reflection and refraction of longitudinal wave from a plane surface separating a micropolar viscoelastic solid half space and a fluid saturated incompressible half space is studied. A longitudinal wave (P-wave) impinges obliquely at the interface. Amplitude ratios for various reflected and transmitted waves have been obtained. Then these amplitude ratios have been computed nu...

Studies of the refraction and dispersion properties of two-dimensional (2D) photonic-crystal (PC) slab waveguides are reported. The photonic band structure is strongly modified in a slab PC, and only a small number of bands satisfy the guiding conditions imposed by the lack of translation symmetry in the direction perpendicular to the slab; however, it was found that a significant number of the...

We present two new techniques for the inversion of first-arrival times to estimate velocity structure. These travel-time inversion techniques are unique in that they do not require the calculation of ray paths. First-arrival times are calculated using a finite-difference scheme that iteratively solves the eikonal equations for the position of the wavefront. The first inversion technique is a di...

We examine the phenomenon of negative refraction using wave packet propagation. The behavior of a single plane wave incident from vacuum onto a flat surface of a medium with a negative index of refraction is solved analytically. The solution requires matching electromagnetic field components across the interface and produces a reflected and a refracted wave in addition to the incident wave. We ...

We investigated negative refraction and subwavelength imaging by a mechanically tunable photonic crystal (PC) slab. A honeycomb-structured PC composed of a silicon–polyimide membrane was used because it exhibits isotropic negative refraction within the second photonic band. Using the finite-difference time-domain (FDTD) method, we demonstrated focusing properties of the PC lenses at various fre...

Purpose To evaluate the visual performance and optical quality of a standardized asymmetric soft contact lens (SCL) used for correction of higher-order aberrations (HOAs) in eyes with keratoconus. Methods We included 30 eyes (26 patients) with keratoconus (average K: 45.7 ± 2.3 diopters [D]). The patients were subjected to corneal tomography, aberrometry, measurements of manifest refraction a...

The influence of refraction when observing a surface or ground target in an airborne radar is considered. In this case, it necessary to take into account the angle photogrammetric atmospheric refraction. However, its behavior not covered literature. ground-based radars, true must be taken account. At high flight altitude, several times larger than angle. Calculation and comparison angles was pe...

background: one of the means of assessing dose to patients from computed tomography (ct) procedure is through the determination of the skin entrance dose (esd) with the appreciation of the concern that ocular exposure effects from ct scan includes possible induction of cancer and cataract. due to the relatively more recent introduction of ct scans, little work has been done in this area in the ...