Anomalous refractive properties of photonic crystals
Journal of the Optical Society of America. A, Optics, image science, and vision./Journal of the Optical Society of America. A, Online,
06/2000
Journal Article
We consider a dielectric photonic crystal made of cylindrical holes in a high index matrix. We show that a given finite size photonic crystal can mimic a homogeneous material whose permittivity and ...permeability are negative. We pay attention to the limitation of the homogeneous medium model and the vital role of the truncation of the crystal.
A simple invisible structure made of two anisotropic homogeneous layers is analyzed theoretically in temporal regime. The frequency dispersion is introduced and analytic expression of the transient ...part of the field is derived for large times when the structure is illuminated by a causal excitation. This expression shows that the limiting amplitude principle applies with transient fields decaying as the power -3/4 of the time. The quality of the cloak is then reduced at short times and remains preserved at large times. The one-dimensional theoretical analysis is supplemented with full-wave numerical simulations in two-dimensional situations which confirm the effect of dispersion.
Splice variants of the signaling lymphocytic activation molecule family 7 (SLAMF7) gene have been identified, and differences in the expression of this gene have been demonstrated at the mRNA level ...in the mammary glands of healthy and mastitis-infected dairy cows. At the same time, significant associations have been found between a deletion in the SLAM7 gene exon, the occurrence of different splice variants, and the occurrence of mastitis in one group of dairy cows. An expression study was conducted on 40 Polish Holstein-Friesian dairy cows of the Black and White variety (group I). Milk samples were taken for microbiological analysis 2 d before slaughter and examined for the presence of bacteria. Immediately after slaughter, mammary tissue samples were taken and divided into 3 groups according to the health status of the mammary gland: healthy (without pathogenic bacteria in milk), coagulase-negative staphylococci (CNS), and coagulase-positive staphylococci (CPS). Based on different SLAMF7 gene DNA fragments, 2 alternative variants of this gene (V1 and V2) and complete gene expression were identified. Separate analyses performed for each isoform showed that the health status of the cow was strongly associated with the expression level of individual variants. The highest expression was detected for the SLAMF7 complete amplicon in healthy cows, and in the CNS and CPS cows the expression of this variant was also higher than V1 and V2. Sanger sequencing was applied to detect the polymorphism/indel variant in the second exon of the SLAMF7 gene probably having the greatest effect on the protein structure and function of SLAMF7. Two genotypes were detected: AA (wild-type) and AB (insertion A). In healthy cows, the frequency of homozygotes AA was higher than the heterozygotes, whereas in the infected animals, the genotypic distribution was the opposite. An association analysis between the identified polymorphism and production traits—including somatic cell count, as well as lactose, protein, and casein content and yield as indicators of subclinical mastitis occurrence—was performed on the group II cows (166 Polish Holstein-Friesian dairy cows). Unfortunately, due to the low number of AB animals, no relationship was demonstrated between genotype in the second exon and the health status of cows. Additionally, the difference in the percentage of SLAMF7-targeted DNA methylation between the groups of animals was not significant, with an average of ∼66 to 68%.
A new analogy between optical propagation and heat diffusion in heterogeneous anisotropic media has been proposed recently by three of the present authors. A detailed derivation of this ...unconventional correspondence is presented and developed. In time harmonic regime, all thermal parameters are related to optical ones in artificial metallic media, thus making possible to use numerical codes developed for optics. Then, the optical admittance formalism is extended to heat conduction in multilayered structures. The concepts of planar microcavities, diffraction gratings and planar transformation optics for heat conduction are addressed. Results and limitations of the analogy are emphasized.
Plasmonic resonances in metallic nanoparticles are exploited to create efficient optical filtering functions. A finite element method is used to model metallic nanoparticle gratings. The accuracy of ...this method is shown by comparing numerical results with measurements on a two-dimensional grating of gold nanocylinders with an elliptic cross section. A parametric analysis is then performed in order to design efficient filters with polarization dependent properties together with high transparency over the visible range. The behavior of nanoparticle gratings is also modeled using the Maxwell-Garnett homogenization theory and analyzed by comparison with the diffraction of a single nanoparticle. The proposed structures are intended to be included in optical systems that could find innovative applications.
Ground-plane cloaks, which transform a curved mirror into a flat one, and recently reported at wavelengths ranging from the optical to the visible spectrum, bring the realm of optical illusion a step ...closer to reality. However, all carpet-cloaking experiments have thus far been carried out in the far field. Here, we demonstrate numerically and experimentally that a dielectric photonic crystal (PC) of an irregular shape made of a honeycomb array of air holes can scatter waves in the near field like a PC with a flat boundary at stop band frequencies. This mirage effect relies upon a specific arrangement of dielectric pillars placed at the nodes of a quasiconformal grid dressing the PC. Our carpet is experimentally shown to flatten the scattered wave fronts of a PC with a bump throughout the range of wavelengths from 1520 to 1580 nm within the stop band extending from 1280 to 1940 nm. The device has been fabricated using a single-mask advanced nanoelectronics technique on III-V semiconductors and the near field measurements have been carried out in order to image the wave fronts' curvatures around the telecommunication wavelength 1550 nm. Interestingly, comparisons of our near-field experimental results with full-wave simulations suggest the relatively low aspect ratio of the fabricated carpet (pillars have 200 nm diameter and 2 mu m height) makes it inherently three dimensional. Moreover, this carpet is constrained to normal incidence. We therefore propose an elaborated design of the carpet (with pillars of varying radii) which should work at different angles of incidence.
Summary
The goal of this study was to demonstrate the usefulness of pedigree data in studies of mitochondrial DNA diversity in dogs and horses. Pedigree information allows for precisely choosing ...animals with distinct haplotypes for analysis, makes it possible to find rare haplotypes present exclusively in single individuals and helps to evaluate haplotype frequencies at the present and in the past. Estimating founder contributions to gene pools enables evaluating the parts of gene pools observed with the help of mtDNA analysis. An important aspect is also the financial benefits: using pedigree data, researchers can save a significant amount of time and money needed for sample collection and laboratory analysis.
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