An Estimation of the Optical Constants of Copper Based on the FEFF 9 Package

The FEFF software package is based on a first-principles real space Green function (RSMS) scattering theory to calculate X-ray absorption fine-structure (XAFS), and forward scattering amplitudes (FSA). From these, an energy-dependent complex dielectric constant can be calculated, and from it other “optical constants”, like the complex index of refraction, absorption coefficient, the reflectance, and energy-loss function, can be derived. A procedure to estimate these using FEFF version 9 is outlined applied to crystalline metallic copper as an example, and the results compared to values taken from the literature.

Anisotropic Complex Refractive Indices of Atomically Thin Materials: Determination of the Optical Constants of Few-Layer Black Phosphorus

In this work, studies of the optical constants of monolayer transition metal dichalcogenides and few-layer black phosphorus are briefly reviewed, with particular emphasis on the complex dielectric function and refractive index. Specifically, an estimate of the complex index of refraction of phosphorene and few-layer black phosphorus is given. The complex index of refraction of this material was extracted from differential reflectance data reported in the literature by employing a constrained Kramers–Kronig analysis combined with the transfer matrix method. The reflectance contrast of 1–3 layers of black phosphorus on a silicon dioxide/silicon substrate was then calculated using the extracted complex indices of refraction.

Low-Cost Particulate Detection in Bleed Air

Bleed air is brought into aircraft cabins in order to maintain the quality of the air for passenger and crew health and comfort. The bleed air can be contaminated by oil due to oil seal leaks in the compressor which have been reported randomly and generated significant public interest. Previous studies have measured the particulate size distribution in the bleed air entering the cabin, but never distinguished the type and material of the particulate matter (PM). The particulates could be potentially hazardous oil droplets from the oil seal leaks, water droplets due the presence of fog generated by the cooling system, and so on. In this study we propose a novel technique using light scattering technology to distinguish between contaminant types. This technique uses size and complex index of refraction as the measure. Since each material has a distinct index of refraction, by determining the index of refraction, our proposed low-cost detector could distinguish the compound in the aerosol as well as determine the particle size simultaneously.

Models of Electromagnetic Response of Materials

Physical models that relate the generalized complex permittivity and complex conductivity to the electronic structure of matter are introduced. The classical models of Drude and Lorentz give expressions for the complex index of refraction in a dielectric, while Drude models a metal as a plasma. Reflection and transmission properties of interfaces are expressed in terms of the complex index of refraction. Special consideration is given to the behavior of light propagation in the frequency vicinity of an atomic resonance of the material. Finally, measurement techniques are presented that are applicable to the determination of the parameters of a Lorentz/Drude representation of electromagnetic transmission in matter.

INVESTIGATION OF COMPLEX INDEX OF REFRACTION OF GALLIUM NITRIDE GaN

An understanding of the complex index of refraction of Gallium Nitride (GaN) is important because of the increasing application of GaN in many high frequency, optical and electronics devices. Complex index of refraction of Gallium Nitride (GaN)have been investigated theoretically by means of Kramers and Kronig method in the photon energy range 2.0 – 10.0eV. We obtained refractive index which has a maximum value of 2.89 at photon energy 7.0eV, the extinction coefficient which has a maximum value of 1.17 at photon energy 7.0eV, the dielectric constant, the real part of the complex dielectric constant has a maximum value of 7.0 at photon energy 7.0eV and the imaginary part of the complex dielectric constant has a maximum value of 6.79 at photon energy 7.0eV, the transmittance which has a maximum value of 0.18 at photon energy 7.0eV, the absorption coefficient which has a maximum value of 86.18 at photon energy 7.0eV. The values obtained for complex index of refraction ofGaN are essentially important for emerging GaN applications such ashigh-power and high-frequency devices, solar cell arrays for satellites, communications and optoelectronics devices.

Influence of Index of Refraction and Particle Size Distribution on Radiative Heat Transfer in a Pulverized Coal Combustion Furnace

In this work, the influence of the radiative properties of coal and ash particles on radiative heat transfer in combustion environments is investigated. Emphasis is placed on the impact on the impact of the complex index of refraction and the particle size on particle absorption and scattering efficiencies. Different data of the complex index of refraction available in the literature are compared, and their influence on predictions of the radiative wall flux and radiative source term in conditions relevant for pulverized coal combustion is investigated. The heat transfer calculations are performed with detailed spectral models. Particle radiative properties are obtained from Mie theory, and a narrow band model is applied for the gas radiation. The results show that, for the calculation of particle efficiencies, particle size is a more important parameter than the complex index of refraction. The influence of reported differences in the complex index of refraction of coal particles on radiative heat transfer is small for particle sizes and conditions of interest for pulverized coal combustion. For ash, the influence of variations in the literature data on the complex index of refraction is larger, here, differences between 10% and 40% are seen in the radiative source term and radiative heat fluxes to the walls. It is also shown that approximating a particle size distribution with a surface area weighted mean diameter, D32, for calculation of the particle efficiencies has a small influence on the radiative heat transfer.