High-Performance Asymmetric Optical Transmission Based on a Dielectric–Metal Metasurface

Asymmetric optical transmission plays a key role in many optical systems. In this work, we propose and numerically demonstrate a dielectric–metal metasurface that can achieve high-performance asymmetric transmission for linearly polarized light in the near-infrared region. Most notably, it supports a forward transmittance peak (with a transmittance of 0.70) and a backward transmittance dip (with a transmittance of 0.07) at the same wavelength of 922 nm, which significantly enhances operation bandwidth and the contrast ratio between forward and backward transmittances. Mechanism analyses reveal that the forward transmittance peak is caused by the unidirectional excitation of surface plasmon polaritons and the first Kerker condition, whereas the backward transmittance dip is due to reflection from the metal film and a strong toroidal dipole response. Our work provides an alternative and simple way to obtain high-performance asymmetric transmission devices.

Salinity and temperature detection for seawater based on a 1D-defective photonic crystal material

In this work, we demonstrate the sensing principle to simultaneously detect the salinity and temperature of seawater using a 1D-defective photonic crystal structure. We designed a one-dimensional defective mode photonic crystal based on the well-known transfer matrix method (TMM) for detecting the seawater salinity and temperature. Our proposed optical sensor is based on the following concept. Since the concentration of the salinity in the seawater changes the refractive index of the seawater, the sensitivity can be calculated by a peak wavelength shift happening in the output transmission spectrum for its variation of different concentration of samples. By adjusting the design parameters of our proposed structure such as the thickness of the defect layer, the temperature and the salinity, we investigated the corresponding optical properties response where the resulted transmittance peak can be turned over the considered range.

Optical crossover phenomenon due to a central 90°-twist defect in a chiral sculptured thin film or chiral liquid crystal

We present a theoretical analysis of a remarkable phenomenon evinced by a periodic structurally chiral material—for example, a chiral sculptured thin film (STF) or a chiral liquid crystal—with a central 90°-twist defect illuminated with normally incident, circularly polarized light. Based on the coupled-wave theory (CWT), an approximate but closed-form solution of the relevant boundary-value problem is obtained in terms of a 4 × 4 CWT transmission matrix. The CWT transmission matrix is decomposed into two terms. The first term favours total transmission in the central part of the Bragg regime of the axially excited, structurally chiral material, while the second term favours total reflection in the whole Bragg regime. When the thickness of the structurally chiral material is relatively small, the second term is dominated by the first, which gives rise to a co-handed transmittance peak in the centre of the Bragg regime. As the thickness increases, the second term becomes significant and interferes with the first term such that the transmission matrix is isomorphic to that of a defect-free structurally chiral material—except in a tiny wavelength-regime wherein the L ∞ -norms of the two terms become identical to engender the total-reflection feature. Hence, the co-handed transmittance peak diminishes (and eventually vanishes) as the thickness increases and is replaced by a cross-handed reflectance peak. The bandwidths of the two peaks depend, in different ways, on the local birefringence of the structurally chiral material.

Properties Of SiC Film As X-Ray Mask Membrane

Many properties of LPCVD SiC film as X-ray mask membrane have been investigated in detail. The film has an atomic ratio of 1.0 and negligible impurities, and was found to be damage-free to SR X-rays up to 500 KJ/cm2. An integrated transparency of 1.05 μm thick SiC membrane for SR X-rays was measured to be 76%. The interference peak at 633 nm of optical spectrum has given the membrane of around 1.0 μm in thickness the transmittance peak of 70% and increased to more than 80% after an AR coating or planarizations by polishing and etching-back. The attainable transmittance was found to be limited to about 84%, theoretically and experimentally, due to the absorption of the membrane. The peak transmittance of 87% is obtainable by the AR coating on the polished SiC membrane. The internal stress was found to be independent of thicknesses above 0.6 μm and the measured Young's modulus is 4.5×1011 Pa irrespective of the thickness and stress. Some extremely polished (0.1 nm Ra) and all the etched-back membranes studied withstood breakage at the pressure as high as the as-deposited ones. The stress uniformity in 30 mm square of the membrane was found to be ± 10 % by measuring five local stresses with a bulge method.

Histology of moose (Alces alces andersoni) interdigital glands and associated green hairs

The interdigital glands of the moose (Alces alces andersoni) are distinguished from the neighboring skin by the lighter epidermis, green hairs, and huge sebaceous and sweat glands. In the glandular area is a shallow fore pocket and deep hind pocket in both sexes and all ages. Special 250 μm thick sections helped reveal the pilosebaceous–sweat gland unit in both the gland and general body surface. The secretory cycle of the apocrine cells and the cycle's relationship to the lipofuscin cycle are described. Macrophages ingest lipofuscin from moribund apocrine cells. The site of the dead apocrine cell is replaced by neighboring epithelial cells spreading out to fill the gap. The green hairs have a transmittance peak at 515 nm. The chemical nature of the coloring matter is unknown but is probably an organic compound covalently bonded to keratin. The green secretion of the sweat gland in some way dyes the hair. In both sexes the sebaceous gland volume of the gland increases at the rut.