Search results for "Refractive index"
showing 10 items of 332 documents
Imprinting the complex dielectric permittivity of liquids into the spintronic terahertz emission
2021
We report an approach in time-domain terahertz (THz) spectroscopy for measuring the dielectric response of liquids based on inherent properties of spintronic THz emitters (STEs). The THz electric field radiated from the STE is inversely proportional to the sum of the complex refractive indices of the media surrounding the thin metallic stack of the STE and the stack's conductivity. We demonstrate that by bringing a liquid in contact with the emitter, its complex refractive index and accordingly its dielectric response are imprinted into the radiated electromagnetic field from the emitter. We use water as the test liquid and ascertain its dielectric loss and permittivity in the range of ∼0.…
Molecular interactions in 1-pentanol +2-methyl-2-butanol mixtures: Static dielectric constant, viscosity and refractive index investigations at 5, 25…
1989
Static dielectric constants, refractive indices and viscosities of 1-pentanol +2-methyl-2-butanol mixtures were measured at 5, 25 and 45°C. The results show that the mixing of the two isomers modifies the polarizability and the resistence of viscous flow of the system depending on the composition and temperature. Short range intermolecular interactions producing hetero-alcohol open dimers are considered.
High-pressure, high-temperature phase diagram of InSe: A comprehensive study of the electronic and structural properties of the monoclinic phase of I…
2006
We report on an investigation of the high-pressure, high-temperature phase diagram of InSe. We optically observed the phase transition from the rhombohedral polytype (InSe-I) to the monoclinic phase (InSe-II) and determined the phase boundary up to $10\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$. High-pressure resistivity measurements were performed to complement the optical measurements. Monoclinic and cubic InSe (InSe-III) were observed to be metastable around $14.5\phantom{\rule{0.3em}{0ex}}\mathrm{GPa}$ and $420\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, and evidence suggesting the existence of an as yet unidentified new high-pressure and high-temperature phase was found. By means of optical ab…
Spectroscopic ellipsometry applied to phase transitions in solids: possibilities and limitations
2009
The possibilities of in situ spectroscopic ellipsometry applied to phase transitions investigation in oxide thin films and crystals are examined in this work, along with the use of various parameters calculated from ellipsometric data (band gap energy Eg, refractive index n and surface roughness) together with the directly measured main ellipsometric angles psi and Delta, for the detection of phase transitions. The efficiency of spectroscopic ellipsometry on "surface" phase transition and its sensitivity to surface defects are also demonstrated.
Ellipsometric studies of behenic acid at the air-water interface
1991
The rich phase behaviour of monolayers of behenic acid (=docosanoic acid) has been analyzed by null ellipsometry in isothermic and isobaric measurements. By using structural data known from x-ray measurements the anisotropy and refractive indices in the vicinity of the S-CS phase transition have been calculated with a minimum of model assumptions. The calculated values are: nsx=1.47. ncsx=1.48. nsz=1.54. ncsz=1.55. and anisotropy γ=nx/nz ≈0.95. It is also shown that ellipsometry is a very sensitive and convenient method of detecting phase transitions. Its value for quantifying the roughness of the monolayer in the close vicinity of phase transitions due to thickness and density fluctuations…
On-line monitoring of one-step laser fabrication of micro-optical components
2002
The use of an on-line monitoring method based on photoelasticity techniques for the fabrication of micro-optical components by means of controlled laser heating is described. From this description it is possible to show in real time the mechanical stresses that form the microelement. A new parameter, stressed area, is introduced that quantifies the stresses of a microelement during its fabrication, facilitating a deeper understanding of the physical phenomena involved in the process as well as being a useful test of quality. It also permits the stress produced in the manufacturing process and the optical properties of the final microelement to be correlated. The results for several microlen…
Study on Structural, Mechanical, and Optical Properties of Al2O3–TiO2 Nanolaminates Prepared by Atomic Layer Deposition
2015
Structural, optical, and mechanical properties of Al2O3/TiO2 nanolaminates fabricated by atomic layer deposition (ALD) were investigated. We performed transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray reflectivity (XRR), energy dispersive X-ray spectroscopy (EDX), ellipsometry, UV–vis spectroscopy, photoluminescence (PL) spectroscopy, and nanointendation to characterize the Al2O3/TiO2 nanolaminates. The main structural, optical, and mechanical parameters of Al2O3/TiO2 nanolaminates (thickness, grain size, refractive index, extinction coefficient, band gap, hardness, and Young’s module) were calculated. It was established that with decreasing of the layer thickness, the …
Efficient excitation of photoluminescence in a two-dimensional waveguide consisting of a quantum dot-polymer sandwich-type structure
2014
International audience; In this Letter, we study a new kind of organic polymer waveguide numerically and experimentally by combining an ultrathin (10–50 nm) layer of compactly packed CdSe/ZnS core/shell colloidal quantum dots (QDs) sandwiched between two cladding poly(methyl methacrylate) (PMMA) layers. When a pumping laser beam is coupled into the waveguide edge, light is mostly confined around the QD layer, improving the efficiency of excitation. Moreover, the absence of losses in the claddings allows the propagation of the pumping laser beam along the entire waveguide length; hence, a high-intensity photoluminescence (PL) is produced. Furthermore, a novel fabrication technology is develo…
The influence of localized plasmons on the optical properties of Au/ZnO nanostructures
2015
Optical and structural experiments have been carried out on Si/ZnO thin films modified with ultra-thin gold layers of different thicknesses. ZnO was produced via Atomic Layer Deposition (ALD) and Au via Physical Vapor Deposition (sputtering). The structural properties of nanostructures were studied by XRD and AFM. Optical characterization was performed by absorbance, photoluminescence (PL) and spectroscopic ellipsometry (SE). A transition from cluster-to-thin films with the increase of Au thickness has been revealed from an analysis of optical and structural parameters. The analysis of optical features of the system has shown that slight changes of the localized plasmon absorption peaks in …
Determining the optical properties of adsorbate covered surfaces by dichroism in VUV-photoemission
1999
The dichroic effects of photoemission excited by polarised light depend on the angle of photon incidence. Measurements of the difference in the angle-resolved photoemission intensities from Cs 5p semi-corelevels excited by photons of opposite helicity, or of orthogonal linear polarisation are reported. It was thought that the dependence of dichroism on the angle of incidence cannot be described using equations omitting metal optics. A complete consideration of the vector potential of the exciting light is needed, including the phase shift between it's parallel and perpendicular components. The phase shift is produced by the complex index of refraction. Using the Fresnel equations for struct…