Domingos De Sousa Meneses

Bio: Domingos De Sousa Meneses is an academic researcher from University of Orléans. The author has contributed to research in topics: Emissivity & Phonon. The author has an hindex of 23, co-authored 107 publications receiving 1618 citations. Previous affiliations of Domingos De Sousa Meneses include Ecole Polytechnique de l'Université d'Orléans & Centre national de la recherche scientifique.

Structure and lattice dynamics of binary lead silicate glasses investigated by infrared spectroscopy

Abstract: The polar lattices dynamics of seven binary lead silicate glasses have been studied by infrared spectroscopy. The analysis of the reflectivity spectra with a dielectric function model, based on a modified Gaussian profile, allows a quantitative evaluation of the presence of lead cations within different structural sites. From the role of the lead cations versus the degree of polymerization of the silicate network and the comparison with literature results, we may to give a scenario for explaining the observed structural evolution of the glass matrix and more particularly the drastic change occurring around 45% of lead content. Below this threshold, lead cations act only as modifiers of the silicate network. Above, the glass structure is deeply modified; a lead network involving around 10% of the lead content appears in glasses whose composition is just above the threshold and progressively grows at the expense of the silicate network with the increase of lead content. For high lead content, lead cations can act as modifiers of the silicate network or as network formers. Results also show that the analysis of far infrared measurements combined with the knowledge of the UV edge optical response is very promising to characterize the local disorder around cations in glasses.

A spectroscopic method to measure the spectral emissivity of semi-transparent materials up to high temperature

Abstract: A spectroscopic method to measure directional spectral emissivity for homogeneous and heterogeneous semi-transparent materials, giving access to a large spectral 10–12 000 cm−1 range and to temperatures lying between 600 and 3000 K is reported Sample heating is supplied by a carbon dioxide laser and the blackbody flux reference is obtained with a lanthanum chromite furnace Experimental results obtained with this setup on several dielectric oxides such as silica, alumina, and magnesia are in good agreement with the results obtained by an indirect method based on the Kirchhoff’s laws A brief overview of the setup abilities and a detailed discussion of the emissivity spectra are also proposed

Causal voigt profile for modeling reflectivity spectra of glasses

Abstract: A new dielectric function model appropriate for a quantitative analysis of infrared spectra of amorphous solids and glasses is introduced and validated by the study of the infrared reflectivity spectra of two different glasses, a calcium aluminosilicate and a borosilicate. Modeling results show its superiority to the classical sum model and confirm its efficiency in the reproduction of the absorption bands of glasses located in the far infrared range.

Temperature Measurement: Christiansen Wavelength and Blackbody Reference

Abstract: The aim of this paper is to propose simple and reliable methods to measure temperatures exceeding 1500°C by pyrometry on dielectric heteropolar compounds. By adopting a spectroscopic approach based on a knowledge of the material (chemical composition, texture, size), it is suggested first to work at the Christiansen wavelength that is nearly independent of temperature, the texture, and the shape. Second, recent developments concerning plate blackbodies that are operable up to 1600 K are presented. Such compact systems are suitable to be installed in industrial heating devices in order to easily calibrate the pyrometer.

Optical constants of silica glass from extreme ultraviolet to far infrared at near room temperature.

Abstract: We thoroughly and critically review studies reporting the real (refractive index) and imaginary (absorption index) parts of the complex refractive index of silica glass over the spectral range from 30 nm to 1000 μm The general features of the optical constants over the electromagnetic spectrum are relatively consistent throughout the literature In particular, silica glass is effectively opaque for wavelengths shorter than 200 nm and larger than 35-40 μm Strong absorption bands are observed (i) below 160 nm due to the interaction with electrons, absorption by impurities, and the presence of OH groups and point defects; (ii) at ~273-285, 35, and 43 μm also caused by OH groups; and (iii) at ~9-95, 125, and 21-23 μm due to SiOSi resonance modes of vibration However, the actual values of the refractive and absorption indices can vary significantly due to the glass manufacturing process, crystallinity, wavelength, and temperature and to the presence of impurities, point defects, inclusions, and bubbles, as well as to the experimental uncertainties and approximations in the retrieval methods Moreover, new formulas providing comprehensive approximations of the optical properties of silica glass are proposed between 7 and 50 μm These formulas are consistent with experimental data and substantially extend the spectral range of 021-7 μm covered by existing formulas and can be used in various engineering applications

Mass production and dynamic imaging of fluorescent nanodiamonds

Abstract: Fluorescent nanodiamond is a new nanomaterial that possesses several useful properties, including good biocompatibility1, excellent photostability1,2 and facile surface functionalizability2,3. Moreover, when excited by a laser, defect centres within the nanodiamond emit photons that are capable of penetrating tissue, making them well suited for biological imaging applications1,2,4. Here, we show that bright fluorescent nanodiamonds can be produced in large quantities by irradiating synthetic diamond nanocrystallites with helium ions. The fluorescence is sufficiently bright and stable to allow three-dimensional tracking of a single particle within the cell by means of either one- or two-photon-excited fluorescence microscopy. The excellent photophysical characteristics are maintained for particles as small as 25 nm, suggesting that fluorescent nanodiamond is an ideal probe for long-term tracking and imaging in vivo, with good temporal and spatial resolution.

Low-loss, infrared and terahertz nanophotonics using surface phonon polaritons

Abstract: The excitation of surface-phonon-polariton (SPhP) modes in polar dielectric crystals and the associ- ated new developments in the field of SPhPs are reviewed. The emphasis of this work is on providing an understand- ing of the general phenomenon, including the origin of the Reststrahlen band, the role that optical phonons in polar dielectric lattices play in supporting sub-diffrac- tion-limited modes and how the relatively long opti- cal phonon lifetimes can lead to the low optical losses observed within these materials. Based on this overview, the achievements attained to date and the potential tech- nological advantages of these materials are discussed for localized modes in nanostructures, propagating modes on surfaces and in waveguides and novel metamaterial designs, with the goal of realizing low-loss nanophoton- ics and metamaterials in the mid-infrared to terahertz spectral ranges.

Phase retrieval, error reduction algorithm, and Fienup variants: a view from convex optimization.

Abstract: The phase retrieval problem is of paramount importance in various areas of applied physics and engineering. The state of the art for solving this problem in two dimensions relies heavily on the pioneering work of Gerchberg, Saxton, and Fienup. Despite the widespread use of the algorithms proposed by these three researchers, current mathematical theory cannot explain their remarkable success. Nevertheless, great insight can be gained into the behavior, the shortcomings, and the performance of these algorithms from their possible counterparts in convex optimization theory. An important step in this direction was made two decades ago when the error reduction algorithm was identified as a nonconvex alternating projection algorithm. Our purpose is to formulate the phase retrieval problem with mathematical care and to establish new connections between well-established numerical phase retrieval schemes and classical convex optimization methods. Specifically, it is shown that Fienup’s basic input–output algorithm corresponds to Dykstra’s algorithm and that Fienup’s hybrid input–output algorithm can be viewed as an instance of the Douglas–Rachford algorithm. We provide a theoretical framework to better understand and, potentially, to improve existing phase recovery algorithms.