scholarly journals THz-TDS Reflection Measurement of Coating Thicknesses at Non-Perpendicular Incidence: Experiment and Simulation

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3473
Author(s):  
Ruben Burger ◽  
Julia Frisch ◽  
Matthias Hübner ◽  
Matthias Goldammer ◽  
Ole Peters ◽  
...  
Keyword(s):  
Refractive Index ◽  
Coating Layer ◽  
Layer Structure ◽  
Measurement Data ◽  
Dielectric Materials ◽  
Thickness Measurement ◽  
Average Error ◽  
Frequency Range ◽  
Sem Images ◽  
Perpendicular Incidence

Time-domain spectroscopy (TDS) in the terahertz (THz) frequency range is gaining in importance in nondestructive testing of dielectric materials. One application is the layer thickness measurement of a coating layer. To determine the thickness from the measurement data, the refractive index of the coating layer must be known in the surveyed frequency range. For perpendicular incidence of the radiation, methods exist to extract the refractive index from the measurement data themselves without prior knowledge. This paper extends these methods for non-perpendicular incidence, where the polarization of the radiation becomes important. Furthermore, modifications considering effects of surface roughness of the coating are introduced. The new methods are verified using measurement data of a sample of Inconel steel coated with yttria-stabilized zirconia (YSZ) and with COMSOL simulations of the measurement setup. To validate the thickness measurements, scanning electron microscopy (SEM) images of the layer structure are used. The results show good agreement with an average error of 1% for the simulation data and under 4% for the experimental data compared to reference measurements.

scholarly journals THz-TDS Reflection Measurement of Coating Thicknesses at Non-Perpendicular Incidence: Experiment and Simulation

2021 ◽  
Author(s):  
Ruben Burger ◽  
Julia Frisch ◽  
Matthias Hübner ◽  
Matthias Goldammer ◽  
Ole Peters ◽  
...  
Keyword(s):  
Refractive Index ◽  
Coating Layer ◽  
Layer Structure ◽  
Measurement Data ◽  
Dielectric Materials ◽  
Thickness Measurement ◽  
Average Error ◽  
Frequency Range ◽  
Sem Images ◽  
Perpendicular Incidence

Time-domain spectroscopy (TDS) in the Terahertz (THz) frequency range is gaining in importance in nondestructive testing of dielectric materials. One application is the layer thickness measurement of a coating layer. To determine the thickness from the measurement data, the refractive index of the coating layer must be known in the surveyed frequency range. For perpendicular incidence of the radiation, methods exist to extract the refractive index from the measurement data itself without prior knowledge. This paper extends these methods for non-perpendicular incidence, where the polarization of the radiation becomes important. Furthermore, modifications considering effects of surface roughness of the coating are introduced. The new methods are verified using measurement data of a sample of Inconel steel coated with yttria-stabilized zirconia (YSZ) and with COMSOL simulations of the measurement setup. To validate the thickness measurements, scanning electron microscopy (SEM) images of the layer structure are used. The results show good agreement with an average error of 1% for the simulation data and under 4% for the experimental data compared to reference measurements.

Electromechanical Response of Multilayered Polymer Films for High Energy Density Capacitors

2011 ◽  
Vol 1312 ◽  
Author(s):  
Mason A. Wolak ◽  
James S. Shirk ◽  
Matt Mackey ◽  
Joel Carr ◽  
Ann Hiltner ◽  
...  
Keyword(s):  
Focused Ion Beam ◽  
Vinylidene Fluoride ◽  
Layer Structure ◽  
Ion Beam ◽  
Dielectric Materials ◽  
High Energy ◽  
High Energy Density ◽  
Breakdown Field ◽  
Sem Images ◽  
Electromechanical Effects

ABSTRACTMultilayered films comprising alternating layers of polycarbonate (PC) and poly(vinylidene fluoride-hexafluoropropylene) (P[VDF-HFP]) show an enhanced dielectric strength (EB> 750 kV/mm) and an increased energy storage density (Ud ~ 13.5 J/cm3) compared to monolithic PC and P[VDF-HFP] films. Here the role of electromechanical effects in the breakdown of multilayer films is explored both by imaging the changes in the layer structure caused by electrical fields below the breakdown field and by a direct measurement of the strain in multilayer PC/ P[VDF-HFP] films subjected to similar fields. Focused Ion Beam (FIB)/ Scanning Electron Microscopy (SEM) images of the layer structure in films subjected to repeated cycles at near-breakdown fields showed local changes in the thickness of individual layers, suggesting that mechanical forces arising from field-induced compression may play a role in the steps preceding the breakdown. The directly measured field induced strain showed evidence for both an elastic and a flow component to the strain. The mechanical responses of films with ≤ 50 vol% P[VDF-HFP] were modeled as simply the sum of an elastic and viscous flow. The observed electromechanical properties vary with the layer structure. This suggests that multilayering polymers may provide a means to mitigate deleterious electromechanical effects in low modulus, high dielectric materials.

Active modulation of refractive index by stress in the terahertz frequency range

2013 ◽  
Vol 52 (25) ◽  
pp. 6364 ◽  
Author(s):  
Lin’an Li ◽  
Wei Song ◽  
Zhiyong Wang ◽  
Shibin Wang ◽  
Mingxia He ◽  
...  
Keyword(s):  
Refractive Index ◽  
Terahertz Frequency ◽  
Frequency Range ◽  
Terahertz Frequency Range

scholarly journals Raman scattering in high-refractive-index nanostructures

Nanophotonics ◽  
2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Søren Raza ◽  
Anders Kristensen
Keyword(s):  
Raman Spectroscopy ◽  
Refractive Index ◽  
Raman Scattering ◽  
Bound States ◽  
Stimulated Raman Scattering ◽  
Dielectric Materials ◽  
High Refractive Index ◽  
Surface Enhanced Raman Spectroscopy ◽  
Raman Enhancement ◽  
The Impact

AbstractThe advent of resonant dielectric nanomaterials has provided a new path for concentrating and manipulating light on the nanoscale. Such high-refractive-index materials support a diverse set of low-loss optical resonances, including Mie resonances, anapole states, and bound states in the continuum. Through these resonances, high-refractive-index materials can be used to engineer the optical near field, both inside and outside the nanostructures, which opens up new opportunities for Raman spectroscopy. In this review, we discuss the impact of high-refractive-index nano-optics on Raman spectroscopy. In particular, we consider the intrinsic Raman enhancement produced by different dielectric resonances and their theoretical description. Using the optical reciprocity theorem, we derive an expression which links the Raman enhancement to the enhancement of the stored electric energy. We also address recent results on surface-enhanced Raman spectroscopy based on high-refractive-index dielectric materials along with applications in stimulated Raman scattering and nanothermometry. Finally, we discuss the potential of Raman spectroscopy as a tool for detecting the optical near-fields produced by dielectric resonances, complementing reflection and transmission measurements.

Long-wavelength lattice vibrations of Ag3In5Se9 and Ag3In5Te9 single crystals — An inversion of LO- and TO-mode frequencies

2016 ◽  
Vol 30 (18) ◽  
pp. 1650229 ◽  
Author(s):  
Nizami Mamed Gasanly
Keyword(s):  
Refractive Index ◽  
Single Crystals ◽  
Longitudinal Optical ◽  
Absorption Index ◽  
Energy Losses ◽  
Optical Parameters ◽  
Lattice Vibrations ◽  
Frequency Range ◽  
Long Wavelength ◽  
Optical Modes

Infrared (IR) reflectivities are registered in the frequency range of 50–2000 cm[Formula: see text] for Ag3In5Se9 and Ag3In5Te9 single crystals grown by Bridgman method. Three infrared-active modes are detected in spectra. The optical parameters, real and imaginary parts of the dielectric function, the function of energy losses, refractive index, absorption index and absorption coefficient were calculated from reflectivity experiments. The frequencies of transverse and longitudinal optical modes (TO and LO modes) and oscillator strength were also determined. The bands detected in infrared spectra were tentatively attributed to various vibration types (valence and valence-deformation). The inversion of LO- and TO-mode frequencies of the sandwiched pair was observed for studied crystals.

Refractive index of micro/nano structured dielectric materials

2007 ◽  
Author(s):  
F. Flory ◽  
L. Escoubas ◽  
J. J. Simon ◽  
P. Torchio ◽  
T. Mazingue ◽  
...  
Keyword(s):  
Refractive Index ◽  
Dielectric Materials

Optically induced birefringence in dye-doped blue phase liquid crystals

2019 ◽  
Vol 46 (6) ◽  
pp. 913-919
Author(s):  
Lin ◽  
Kuo ◽  
Huang ◽  
Wu ◽  
Lin ◽  
...  
Keyword(s):  
Refractive Index ◽  
Liquid Crystal ◽  
Pump Beam ◽  
Pump Intensity ◽  
Photoinduced Change ◽  
Methyl Red ◽  
Sem Images ◽  
Photoinduced Birefringence ◽  
Phase Liquid ◽  
Blue Phase

This paper investigates the photoinduced change of refractive index in dye (methyl red, MR)-doped blue phase (DDBP) cells by illumination of a pump beam. Through excitation of light irradiation with proper photon energy, MR can transform from trans-state to cis-state and successively diffuse and anisotropically adsorb on the inner glass substrate of the DDBP cell along the direction perpendicular to the polarisation of the pump beam. The adsorbed MR molecules can effectively rotate the orientation of the liquid crystal (LC) molecules and thereby modulate the effective refractive index of the DDBP cell. The SEM images of the adsorbed regions of the illuminated DDBP samples were also taken for discussing the relation between the pump intensity and the photoinduced birefringence.

An Optical Differentiator Based on a Three-Layer Structure with a W-Shaped Refractive Index Profile

2018 ◽  
Vol 127 (2) ◽  
pp. 202-209 ◽  
Author(s):  
N. V. Golovastikov ◽  
L. L. Doskolovich ◽  
E. A. Bezus ◽  
D. A. Bykov ◽  
V. A. Soifer
Keyword(s):  
Refractive Index ◽  
Layer Structure ◽  
Refractive Index Profile ◽  
Index Profile ◽  
Optical Differentiator

Growth and Characterization of Uniform Carbon Nanotube Arrays on Active Substrates

2015 ◽  
Vol 1752 ◽  
pp. 3-14
Author(s):  
Qiuhong Zhang ◽  
Betty T. Quinton ◽  
Bang-Hung Tsao ◽  
James Scofield ◽  
Neil Merrett ◽  
...  
Keyword(s):  
Buffer Layer ◽  
Layer Structure ◽  
Substrate Surface ◽  
Composite Layer ◽  
Carbon Composite ◽  
Thermal Interface Material ◽  
Chemical Vapor Deposition Method ◽  
Sem Images ◽  
Reactive Material ◽  
Aspect Ratios

ABSTRACTCarbon nanotubes (CNTs) have unique thermal/electrical/mechanical properties and high aspect ratios. Growth of CNTs directly onto reactive material substrates (such as metals and carbon based foam structures, etc.) to create a micro-carbon composite layer on the surface has many advantages: possible elimination of processing steps and resistive junctions, provision of a thermally conductive transition layer between materials of varying thermal expansion coefficients, etc. Compared to growing CNTs on conventional inert substrates such as SiO2, direct growth of CNTs onto reactive substrates is significantly more challenging. Namely, control of CNT growth, structure, and morphology has proven difficult due to the diffusion of metallic catalysts into the substrate during CNT synthesis conditions. In this study, using a chemical vapor deposition method, uniform CNT layers were successfully grown on copper foil and carbon foam substrates that were pre-coated with an appropriate buffer layer such as Al2O3 or Al. SEM images indicated that growth conditions and, most notably, substrate surface pre-treatment all influence CNT growth and layer structure/morphology. The SEM images and pull-off testing results revealed that relatively strong bonding existed between the CNT layer and substrate material, and that normal interfacial adhesion (0.2‒0.5 MPa) was affected by the buffer layer thickness. Additionally, the thermal properties of the CNT/substrate structure were evaluated using a laser flash technique, which showed that the CNT layer can reduce thermal resistance when used as a thermal interface material between bonded layers.

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