X-ray reflectivity of chemically vapor-deposited diamond single crystals in the Laue geometry

The absolute X-ray reflectivity of chemically vapor-deposited (CVD) single-crystal diamond plates was measured in the Laue geometry in the double-crystal non-dispersive setting with an asymmetric Si beam-conditioner crystal. The measurements were supplemented by rocking-curve topography. The measured reflectivity curves are examined in the framework of the Darwin–Hamilton approach using a set of two independent parameters: the characteristic thickness of mosaic blocks and their average angular misorientation. Owing to strong extinction effects, the width of the reflectivity curves does not directly represent the average misorientation of the blocks. Two different sets of parameters were found for the 111 asymmetric reflection in the two different scattering configurations (beam compression and beam expansion). Analysis of the rocking-curve topographs shows that this discrepancy can be attributed to inhomogeneity of the diamond crystal microstructure.

Bianisotropic metasurfaces: physics and applications

Metasurfaces as optically thin composite layers can be modeled as electric and magnetic surface current sheets flowing in the layer volume in the metasurface plane. In the most general linear metasurface, the electric surface current can be induced by both incident electric and magnetic fields. Likewise, magnetic polarization and magnetic current can be induced also by external electric field. Metasurfaces which exhibit magnetoelectric coupling are called bianisotropic metasurfaces. In this review, we explain the role of bianisotropic properties in realizing various metasurface devices and overview the state-of-the-art of research in this field. Interestingly, engineered bianisotropic response is seen to be required for realization of many key field transformations, such as anomalous refraction, asymmetric reflection, polarization transformation, isolation, and more. Moreover, we summarize previously reported findings on uniform and gradient bianisotropic metasurfaces and envision novel and prospective research directions in this field.