Enlarged Photonic Band Gap in Heterostructure of Metallic Photonic and Superconducting Photonic Crystals

We show theoretically that the frequency range of photonic band gap of a hetero-structure which is made of a metallic photonic and superconducting photonic crystal can be enlarged due to the combination of the reflection band properties of the superconductor–dielectric (PC1) and metallic–dielectric (PC2) periodic structures. The transmittance and band structure of the considered structures are calculated using simple transfer matrix method and the Bloch theorem. Beside this, we have also calculated the transmittance of the superconducting photonic structure (PC1), metallic photonic structure (PC2) and heterostructure of metallic photonic and superconductor photonic crystals (PC1/PC2) for TE and TM-mode at the different angles of incidence.     

Photonic Crystals

Abstract

In this paper, we review the early motivation for photonic crystal research which was derived from the need for a photonic bandgap in quantum optics. This led to a series of experimental and theoretical searches for the elusive photonic bandgap structures: those three-dimensionally periodic dielectric structures which are to photon waves, as semiconductor crystals are to electron waves. We shall describe how the photonic semiconductor can be ‘doped’, producing tiny electromagnetic cavities. Finally, we shall summarize some of the anticipated implications of photonic band structure for quantum electronics and the prospects for the creation of photonic crystals in the optical domain.     

Maximization of Photonic Bandgaps in Two-Dimensional Superconductor Photonic Crystals

In this paper, we investigate the properties of photonic band structures in two-dimensional superconductor photonic crystals (2D-SCPCs) using the frequency dependent plane wave expansion method. We consider two types of 2D-SCPCs, which are composed of superconductor (dielectric) rods embedded into a dielectric (superconductor) background, named type I (type II) SCPCs. We target maximization of the gap-to-mid-gap ratio by varying many parameters, namely, shape of the rods, the operating temperature, the permittivity of the dielectric material, and the threshold frequency of the superconductor. We show that the type II SCPCs have a higher gap-to-mid-gap ratio than the type I SCPCs. In addition, the PBGs can be tuned efficiently by the operating temperature. Moreover, the photonic band structures can be tailored by changing the dielectric constant of the background (rods) in the type I (type II) SCPCs.     

Photonic textile fibers

The characterization of the emission from nylon fibers containing laser dyes and TIO(2) nanoparticle scatterers indicates laser behavior with linewidths as low as 4 nm in 200- to 800-μm fibers. These materials can be used to produce lasing textiles, which can be used to produce photonic codes for a variety of civilian and military applications.     

Some Vibrational-Rotational Bands of Deuterated Methanes

A parallel band at 2,200 cm⁻¹ and a perpendicular band at 2,780 cm⁻¹ of CH₃D have been observed under high resolution and analysed. The analysis of the perpendicular band revealed the presence of l-type doubling in the doubly degenerate excited state. From the analysis of the parallel band it is found that B₀= 3.880 cm⁻¹. A hybrid band of CD₃H has been observed near 2,600 cm⁻¹. Both active components, A and E are observed and analysed. The ground state B₀ value found from this analysis is in good agreement with previous determinations.     

Optical Sum Rule in Finite Bands

In a single finite electronic band the total optical spectral weight or optical sum carries information on the interactions involved between the charge carriers as well as on their band structure. It varies with temperature as well as with impurity scattering. The single band optical sum also bears some relationship to the charge carrier kinetic energy and, thus, can potentially provide useful information, particularly on its change as the charge carriers go from normal to superconducting state. Here we review the considerable advances that have recently been made in the context of high T_c oxides, both theoretical and experimental.     

有层次的幺半群带的结构

给出了有层次的幺半群带的一种扭组织积结构,并由此得出正常的幺半群带的织积结构。     

一维光子晶体的带隙特性研究

一维光子晶体是指介质只在一个方向成周期性排列的材料。利用薄膜光学的特征矩阵法研究了一维光子晶体的禁带特性,分析了填充率变化、厚度的随机扰动对光子带隙的影响。结果表明,随着填充率的变化,各能级的带隙率变化,并且存在一个极大值;厚度的随机扰动对光子带隙也有一定的影响,随机度不同,对光子带隙的影响也不一样。本研究对一维光子晶体的设计与制备有一定的参考价值。     

Photonic crystal beam splitters

This work studies two-dimensional photonic crystal beam splitters with two input ports and two output ports. The beam splitter structure consists of two orthogonally crossed line defects and one point defect in square-lattice photonic crystals. The point defect is positioned at the intersection of the line defects to divide the input power into output ports. If the position and the size of the point defect are varied, the power of two output ports can be identical. The beam splitters can be used in photonic crystal Mach-Zehnder interferometers or switches. The simulation results show that a large bandwidth of the extinction ratio larger than 20 dB can be obtained while two beams are interfered in the beam splitters. This enables photonic crystal beam splitters to be used in fiber optic communication systems.     

Superconductor-Semiconductor Metamaterial Photonic Crystals

We constructed theoretically one-dimensional photonic crystal (1DPC) by using a semiconductor metamaterial in the near-infrared range(NIR) which is composed of Al-doped Z n O(A Z O) and Z n O. The construction of this photonic crystal (PC) is based on a high-temperature superconductor material with the semiconductor metamaterial as constituent layers for this PC. The electromagnetic interactions with this periodic structure are investigated using the transfer matrix method (TMM) in the NIR range. The investigation shows that the reflectance spectra are depending on some parameters of the periodic structure such as the thicknesses of the constituent layers, temperature, and the angle of incidence.     

Formation of Electron Strings in Narrow Bands

Electron strings may arise in polar materials as a result of an electronic phase separation. The width or the transverse diameter of the string is equal to one interatomic spacing. The length of the string depends on dielectric constants of semiconductors. The appearance of these electron strings may naturally explain the effect of stripe formation observed in a variety of HTSC experiments.     

Theory of Fermi Liquid with Flat Bands

A self-consistent theory of Fermi systems hosting flat bands is developed. Compared with an original model of fermion condensation, its key point consists in proper accounting for mixing between condensate and non-condensate degrees of freedom that leads to formation of a non-BCS gap \(\Upsilon (\mathbf{p})\) in the single-particle spectrum. The results obtained explain: (1) the two-gap structure of spectra of single-particle excitations of electron systems of copper oxides, revealed in ARPES studies, (2) the role of violation of the topological stability of the Landau state in the arrangement of the \(T-x\) phase diagram of this family of high-\(T_\mathrm{c}\) superconductors, (3) the topological nature of a metal–insulator transition, discovered in homogeneous two-dimensional low-density electron liquid of MOSFETs more than 20 years ago.     

Uniform Confidence Bands for a Quadratic Model

In this paper uniform confidence bands are developed for a quadratic regression model. Tables are supplied to determine a uniform confidence band for the quadratic model in which it is assumed the sum of the cubed deviations of the independent variable about its mean is equal to zero. The uniform confidence band is then compared with the classical competitor, the Scheffit confidence band. A table summarizing the results of this comparison is presented. Finally, an example is examined.     

左阿基米德序半群的自然序带

刻划了分别可分解为左阿基米德序半群,左单序半群的幂零拆张序半群和左单序半群的自然序带的序半群的特征。     

Metallic and Superconducting Photonic Crystal

We have investigated the transmittance for two kinds of photonic crystals; (i) One-dimensional metallic photonic crystals (1DMPCs) and (ii) One-dimensional superconducting photonic crystals (1DScPCs). The variance of the intensity and the bandwidth of the transmittance are strongly dependent on the thicknesses and frequencies. We have compared the transmittance spectra in 1DScPCs and 1DMPCs at low frequencies, and we present some details about the transmittance spectra by using Transfer Matrix Method (TMM) at the same conditions.      

The Effect of Friction on Wide Shear Bands

Frictional and frictionless granular materials in a split-bottom ring shear cell geometry show wide shear bands under slow, quasi-static deformation. Here, the differences between frictional and frictionless materials are elaborated using discrete element simulations (DEM). Several continuum fields like the density, the velocity field, the deformation gradient, and the stress are used here for comparison.

Interestingly, the shear stress intensity, i.e., the shear stress divided by the pressure, is approximately constant throughout the wide shear band, as long as the strain rate is large enough—indicating a Mohr-Coulomb type yield stress fluid. The “viscosity,” i.e., the shear stress divided by the strain rate, is proportional to the pressure, which is increasing with the contact number density. Furthermore, the viscosity is inversely proportional to the nondimensional strain rate, indicating shear softening behavior inside the wide shear bands.