Nanofoam Porosity Measured by Infrared Spectroscopy and Refractive Index

1996 ◽  
Vol 431 ◽  
Author(s):  
M. I. Sanchez ◽  
J. L. Hedrick ◽  
T. P. Russell
Keyword(s):  
Refractive Index ◽  
Infrared Spectroscopy ◽  
Effective Medium Theory ◽  
Gradient Methods ◽  
Quantitative Agreement ◽  
Spherical Particles ◽  
Void Content ◽  
Absorption Bands ◽  
Medium Theory ◽  
Poly Propylene

AbstractInfrared spectroscopy and optical waveguide were used to determine the porosity of polymer nanofoams produced from block copolymers of an aromatic polyimide endcapped with either poly(propylene oxide) or poly(a-methylstyrene). The infrared absorption bands and film thickness were compared to those of the neat homopolymer to yield an accurate measure of the void content. The porosity was also determined by measuring the refractive index and using the Maxwell-Garnett effective medium theory for spherical particles. Both techniques are in quantitative agreement with density gradient methods.

IMPEDANCE-MATCHED MULTILAYERED STRUCTURE CONTAINING A ZERO-PERMITTIVITY MATERIAL FOR SPATIAL FILTERING

2008 ◽  
Vol 17 (03) ◽  
pp. 349-355 ◽  
Author(s):  
YI JIN ◽  
SAILING HE
Keyword(s):  
Refractive Index ◽  
Periodic Structure ◽  
Free Space ◽  
Effective Medium Theory ◽  
Special Property ◽  
Spatial Filtering ◽  
Spatial Filter ◽  
Multilayered Structure ◽  
Total Thickness ◽  
Medium Theory

Based on the effective medium theory, a multilayered spatial filter is constructed with an ultralow-permittivity material and a typical dielectric. Besides the special property of an ultralow refractive index, the designed periodic structure is impedance-matched to free space, regardless of the total thickness. The present spatial filter works well even when moderate loss exists.

Wide-band effective medium theory for a cubic array of metallic spherical particles

Optik ◽  
2020 ◽  
Vol 206 ◽  
pp. 164336 ◽  
Author(s):  
Oleg Rybin ◽  
Sergey Shulga ◽  
Muhammad Raza
Keyword(s):  
Effective Medium Theory ◽  
Wide Band ◽  
Effective Medium ◽  
Spherical Particles ◽  
Medium Theory

An Effective Unit Cell Approach to Compute the Thermal Conductivity of Composites With Cylindrical Particles

2005 ◽  
Vol 127 (6) ◽  
pp. 553-559 ◽  
Author(s):  
Deepak Ganapathy ◽  
Kulwinder Singh ◽  
Patrick E. Phelan ◽  
Ravi Prasher
Keyword(s):  
Thermal Conductivity ◽  
Effective Medium Theory ◽  
Effective Medium ◽  
Unit Cell ◽  
Spherical Particles ◽  
Medium Theory ◽  
Volume Fractions ◽  
Curvature Effects ◽  
Finite Differences Method ◽  
Cylindrical Particles

This paper introduces a novel method, combining effective medium theory and the finite differences method, to model the effective thermal conductivity of cylindrical-particle-laden composite materials. Typically the curvature effects of cylindrical or spherical particles are ignored while calculating the thermal conductivity of composites containing such particles through numerical techniques, such that the particles are modeled as cuboids or cubes. An alternative approach to mesh the particles into small volumes is just about impossible, as it leads to highly intensive computations to get accurate results. On the other hand, effective medium theory takes the effect of curvature into account, but cannot be used at high volume fractions because it does not take into account the effects of percolation. In this paper, a novel model is proposed where the cylindrical particles are still treated as squares (cuboids), but to capture the effect of curvature, an effective conductivity is assigned to the particles by using the effective medium approach. The authors call this the effective unit cell approach. Results from this model for different volume fractions, on average, have been found to lie within ±5% of experimental thermal conductivity data.

scholarly journals Detection Limit for Optically Sensing Specific Protein Interactions in Free-solution

2017 ◽  
Author(s):  
Harish Sasikumar ◽  
Manoj M. Varma
Keyword(s):  
Refractive Index ◽  
Protein Interactions ◽  
Effective Medium Theory ◽  
Refractive Index Change ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Medium Theory ◽  
Index Change ◽  
Interacting Species

Optical molecular sensing techniques are often limited by the refractive index change associated with the probed interactions. In this work, we present a closed form analytical model to estimate the magnitude of optical refractive index change arising from protein-protein interactions. The model, based on the Maxwell Garnett effective medium theory and first order chemical kinetics serves as a general framework for estimating the detection limits of optical sensing of molecular interactions. The model is applicable to situations where one interacting species is immobilized to a surface, as commonly done, or to emerging techniques such as Back-Scattering Interferometry (BSI) where both interacting species are un-tethered. Our findings from this model point to the strong role of as yet unidentified factors in the origin of the BSI signal resulting in significant deviation from linear optical response. <br>

Plasmonic biosensor based on an effective medium theory as a simple tool to predict and analyze refractive index changes

2020 ◽  
Vol 131 ◽  
pp. 106332
Author(s):  
Gesuri Morales-Luna ◽  
Marcela Herrera-Domínguez ◽  
Eduardo Pisano ◽  
Alejandro Balderas-Elizalde ◽  
Raul I. Hernandez-Aranda ◽  
...  
Keyword(s):  
Refractive Index ◽  
Effective Medium Theory ◽  
Effective Medium ◽  
Medium Theory ◽  
Simple Tool ◽  
Index Changes

scholarly journals Dual-Band Light Absorption Enhancement in Hyperbolic Rectangular Array

2019 ◽  
Vol 9 (10) ◽  
pp. 2011 ◽  
Author(s):  
Honglong Qi ◽  
Tian Sang ◽  
La Wang ◽  
Xin Yin ◽  
Jicheng Wang ◽  
...  
Keyword(s):  
Light Absorption ◽  
Effective Medium Theory ◽  
Impedance Matching ◽  
Dual Band ◽  
Absorption Enhancement ◽  
Absorption Bands ◽  
Absorption Properties ◽  
Rectangular Array ◽  
Medium Theory ◽  
Band Absorption

The effect of dual-band light absorption enhancement in a hyperbolic rectangular array (HRA) is presented. The enhanced light absorption of the HRA results from the propagating surface plasmon (PSP) resonance, and a dual-band absorption with low and flat sideband level can be realized. The impedance theory is used to evaluate the absorption properties of the HRA, and shows that the input impedances of the HRA varied abruptly around the absorption bands to meet the impedance matching. The absorption spectra of the HRA can be estimated using the effective medium theory (EMT), and its accuracy can be improved as the number of film stacks is increased. The dual-band absorptions of the HRA are very robust to the variations of the width and the number of film stack. Potential application in refractive index sensing can be achieved by utilizing the two absorption bands.

Band structure of one-dimensional doped photonic crystal with three level atoms using the Fresnel coefficients method

2018 ◽  
Vol 32 (01) ◽  
pp. 1750277
Author(s):  
A. Jafari ◽  
A. Rahmat ◽  
S. Bakkeshizadeh
Keyword(s):  
Refractive Index ◽  
Photonic Crystal ◽  
Band Structure ◽  
Effective Medium Theory ◽  
Electric Permittivity ◽  
Filling Rate ◽  
Medium Theory ◽  
One Dimensional ◽  
Layered Dielectrics ◽  
Fresnel Coefficients

We consider a one-dimensional photonic crystal (1DPC) composed of double-layered dielectrics. Electric permittivity and magnetic permeability of this crystal depends on the incident electromagnetic wave frequency. We suppose that three level atoms have been added to the second layer of each dielectric and this photonic crystal (PC) has been doped. These atoms can be added to the layer with different rates. In this paper, we have calculated and compared the band structure of the mentioned PC considering the effect of added atoms to the second layer with different rates through the Fresnel coefficients method. We find out that according to the effective medium theory, the electric permittivity of the second layer changes. Also the band structure of PC for both TE and TM polarizations changes, too. The width of bandgaps related to “zero averaged refractive index” and “Bragg” increases. Moreover, new gap branches appear in new frequencies at both TE and TM polarizations. In specific state, two branches of “zero permittivity” gap appear in the PC band structure related to TM polarization. With increasing the amount of the filling rate of total volume with three level atoms, we observe a lot of changes in the PC band structure.

An Effective Unit Cell Approach to Compute the Thermal Conductivity of Composites With Cylindrical Particles

2003 ◽  
Author(s):  
Deepak Ganapathy ◽  
Kulwinder Singh ◽  
Patrick E. Phelan ◽  
Ravi S. Prasher
Keyword(s):  
Thermal Conductivity ◽  
Effective Conductivity ◽  
Effective Medium Theory ◽  
Effective Medium ◽  
Unit Cell ◽  
Spherical Particles ◽  
Medium Theory ◽  
Volume Fractions ◽  
Finite Differences Method ◽  
Cylindrical Particles

This paper introduces a novel method to model the effective thermal conductivity of cylindrical-particle-laden composite materials. This modeling methodology is a combination of the effective medium theory and the finite differences method. Typically the curvature effects of cylindrical or spherical particles are ignored while calculating the thermal conductivity of composites containing such particles through numerical techniques. These particles are modeled as cuboids or cubes. Numerical modeling of circular/spherical geometries as cubes or cuboids will lead to wrong conclusions due to two reasons: (i) It does not capture the effect of curvature on heat flow, i.e., constriction of heat flux lines near the particles due to shape, (ii) It assigns higher effective conductivity to the particles as the cubes or the cuboids have larger volume and surface area. An alternative approach to mesh the particles into small volumes is just about impossible as it leads to highly intensive computational algorithms to get accurate results. On the other hand, effective medium theory takes the effect of curvature into account but it cannot be used at high volume fractions because it does not take into account the effects of percolation. In this paper, a novel model is proposed where the cylindrical particles are still treated as squares (cuboids) but to capture the effect of curvature, an effective conductivity is assigned to the particles by using the effective medium approach. The authors call this the effective unit cell approach. Results from this model for different volume fractions, on average, have been found to lie within ±5% of experimental thermal conductivity data.

scholarly journals Detection Limit for Optically Sensing Specific Protein Interactions in Free-solution

2017 ◽  
Author(s):  
Harish Sasikumar ◽  
Manoj M. Varma
Keyword(s):  
Refractive Index ◽  
Protein Interactions ◽  
Effective Medium Theory ◽  
Refractive Index Change ◽  
Specific Protein ◽  
Protein Protein Interactions ◽  
Medium Theory ◽  
Index Change ◽  
Interacting Species

Optical molecular sensing techniques are often limited by the refractive index change associated with the probed interactions. In this work, we present a closed form analytical model to estimate the magnitude of optical refractive index change arising from protein-protein interactions. The model, based on the Maxwell Garnett effective medium theory and first order chemical kinetics serves as a general framework for estimating the detection limits of optical sensing of molecular interactions. The model is applicable to situations where one interacting species is immobilized to a surface, as commonly done, or to emerging techniques such as Back-Scattering Interferometry (BSI) where both interacting species are un-tethered. Our findings from this model point to the strong role of as yet unidentified factors in the origin of the BSI signal resulting in significant deviation from linear optical response. <br>

A Study of Thin Films of Indium Tin Oxide Using Spectroscopic Ellipsometry

1992 ◽  
Vol 280 ◽  
Author(s):  
Colette Maloney ◽  
N. Bogdanova Arn
Keyword(s):  
Tin Oxide ◽  
Indium Tin Oxide ◽  
Effective Medium Theory ◽  
Blue Shift ◽  
Electron Beam Evaporation ◽  
Refractive Indices ◽  
Void Content ◽  
Medium Theory ◽  
Force Microscopy ◽  
Electrically Conducting

ABSTRACTTransparent, electrically conducting, indium tin oxide films were prepared by r.f. reactive sputtering and electron beam evaporation. The refractive indices, n, and extinction coefficients, k, of the films together with their thicknesses were determined from spectroscopic (250nm–750nm) ellipsometry measurements. Elucidation of these parameters allowed an evaluation of the influence of the deposition conditions on the morphology, stoichionietry and microstructure of the films.Using effective medium theory the effect of the oxygen concentration on the void content of the sputtered films could be modelled. At concentrations greater than 15–20%, a saturation in the optical properties was observed as the films approached ideal stoichionietry. The refractive indices of both annealed and untreated evaporated films exhibited a decrease with increasing substrate temperature (up to 300°C) which is consistent with an increase in the microcrystallite size. Measurements on the annealed samples revealed a blue-shift in both n and k spectra as the oxygen pressure during evaporation was reduced to the background value of about 106 mbar. This, we attribute to the Burstein-Moss shift associated with the increased number of oxygen vacancies.Supplementary investigations using profilometry, atomic force microscopy and optical transmission spectroscopy confirm the reliability of the results obtained by this technique.

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