Search results for "Refractive"
showing 10 items of 559 documents
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…
Laser wavelength effects on the refractive index change of waveguides written by femtosecond pulses in silica glasses
2018
We investigate the influence of two fs-laser wavelengths (343 and 800 nm) on the induced refractive index change (Δn) of waveguides written in silica materials. Results show that Δn is higher for waveguides photo-inscribed with UV photons.
Scanning optical microscopy modeling in nanoplasmonics
2012
International audience; One of the main purposes of nanoplasmonics is the miniaturization of optical and electro-optical components that could be integrable in coplanar geometry. In this context, we propose a numerical model of a polarized scanning optical microscope able to faithfully reproduce both photon luminescence and temperature distribution images associated with complex plasmonic structures. The images are computed, pixel by pixel, through a complete self-consistent scheme based on the Green dyadic functions (GDF) formalism. The basic principle consists in the numerical implementation of a realistic three-dimensional light beam acting as a virtual light tip able to probe the volume…
Real-time and low-cost sensing technique based on photonic bandgap structures
2011
[EN] A technique for the development of low-cost and high-sensitivity photonic biosensing devices is proposed and experimentally demonstrated. In this technique, a photonic bandgap structure is used as transducer, but its readout is performed by simply using a broadband source, an optical filter, and a power meter, without the need of obtaining the transmission spectrum of the structure; thus, a really low-cost system and real-time results are achieved. Experimental results show that it is possible to detect very low refractive index variations, achieving a detection limit below 2 x 10(-6) refractive index units using this low-cost measuring technique. (C) 2011 Optical Society of America[
Formación de estructuras no lineales mediante control de la fase en sistemas fotorrefractivos
2018
Esta tesis doctoral se ha realizado en el campo de la Óptica No Lineal experimental, dentro de un marco de investigación básica. El objeto de estudio es la manipulación experimental de estructuras que pueden emerger en la sección transversal de un haz láser bajo determinadas condiciones, y que además están caracterizadas por su fase: como, por ejemplo, vórtices, solitones o dominios de fase. Como elemento activo no lineal que contribuye a la generación de este tipo de estructuras, se utilizan diferentes tipos cristal fotorrefractivos (PRCs) con tiempos de respuesta largos como el BaTiO3 y el SBN o tiempos cortos como el KTLN. El presente manuscrito está redactado como un compendio de artícu…