Search results for "Transmittance"
showing 10 items of 89 documents
Spectral Transmission of the Human Corneal Layers
2021
Este artículo se encuentra disponible en la siguiente URL: https://www.mdpi.com/2077-0383/10/19/4490 Este artículo de investigación pertenece a la sección "Ophthalmology". We have assessed the spectral transmittance of the different layers of the human cornea in the ultraviolet (UV), visible, and near-infrared (IR) spectral ranges. Seventy-four corneal sample donors were included in the study. Firstly, the corneal transmittance was measured using a spectrophotometer. Then, all samples were fixed for histopathological analysis, which allowed us to measure the thickness of each corneal layer. Finally, the absorption coefficients of the corneal layers were computed by a linear model reproducin…
Numerical analysis of thermally induced optical nonlinearity in GaSe layered crystal
1996
A numerical approach to studying thermally induced optical nonlinearity in semiconductors is presented. A transient finite difference algorithm is applied to solve the thermal diffusion equation coupled with the nonlinear absorbance-transmittance of Au/GaSe/Au samples with an applied electric field. The presented analysis can deal with any arbitrary axisymmetric dependence of the input power over the sample and external electric field, and provides information about the steady state and transitory effects in the transmittance.
Spectral Transmittance of Intraocular Lenses under Natural and Artificial Illumination
2011
Purpose To compare the spectral transmission of different intraocular lenses (IOLs) with either ultraviolet (UV) or blue-light filters, and to analyze the performance of these filters with artificial light sources as well as sunlight. Design Experimental study. Methods The spectral transmission curve of 10 IOLs was measured using a PerkinElmer Lambda 800 UV/VIS spectrometer (Waltham, MA). Different filtering simulations were performed using the D65 standard illuminant as daylight and standard incandescent lamp and fluorescent bulb illuminants. Main Outcomes Measures Spectral transmittance of the IOLs. Results All the IOLs studied provide good UVC (200–280 nm) and UVB (280–315 nm) protection…
Experimental Evidence on the Thermal Performance of Opaque Surfaces in Mediterranean Climate
2013
The thermal insulation of buildings, intended as wrap feature which determines the dispersion of heat, the reference parameter is necessary to contain the thermal losses during the winter season. The transmittance of the opaque components, used as an indicator of the energy quality of a casing, together with the overall coefficient of dispersion, represents a proper descriptor of the behavior during the heating season. However, if a strong insulation in winter conditions brings only positive effects, the same cannot be said for the summer conditions. A high value of the insulation in the casing is convenient only when the gains free, either in the form of solar contribution that of endogeno…
The thermophysical characterization of technical elements in the historic architecture: experiences in Palermo
2014
Per contemperare il miglioramento delle prestazioni energetiche e ambientali dell'architettura storica con l'esigenza della sua conservazione, è necessario analizzare le caratteristiche termofisiche dei materiali e degli elementi tecnici che la connotano. Tuttavia la disponibilità di pochi dati in merito si somma alle disomogeneità tipiche della costruzione storica e alle difficoltà di analisi ad esse connesse. In particolare, per la trasmittanza termica delle murature storiche, la letteratura scientifica evidenzia scostamenti anche notevoli tra i valori desunti da misure in situ e quelli calcolati, in genere superiori ai primi. Il contributo espone gli obiettivi e la metodologia di un prog…
Bloch Modes Coupling in Photonic Crystal Waveguides
2005
We investigate the properties of Bloch modes inside a photonic crystal waveguide. By using simultaneously a near field optical microscope and a transmittance setup, we demonstrate that Bloch modes having different parity are coupled.
Natural optical anisotropy of h-BN: Highest giant birefringence in a bulk crystal through the mid-infrared to ultraviolet range
2018
The giant birefringence of layered h-BN was demonstrated by analyzing the interference patterns in reflectance and transmittance measurements in the mid-infrared to the deep ultraviolet energy range. The refractive index for polarization perpendicular to the c axis is much higher than the refractive index for polarization parallel to the c axis, and it displays a strong increase in the ultraviolet range that is attributed to the huge excitonic effects arising from the unique electronic structure of h-BN. Thus, h-BN is shown to exhibit a giant negative birefringence that ranges from -0.7 in the visible to -2 in the deep ultraviolet close to the band gap. The electronic dielectric constants f…
Towards an efficient epsilon near-zero-based wavefront shaper
2017
Although epsilon-near-zero (ENZ) metamaterials offer many unconventional ways to play with light, the optical impedance mismatch with surroundings can limit the efficiency of future devices. An original example of ENZ-based applications is the wavefront shaping, but up to now devices have transmission efficiency as low as 10-5 [1]. Here, we report strategies to enhance the transmittance through ENZ layer and we demonstrate an enhancement by four orders of magnitude of the transmittance, which reaches up to 15% in the context of ENZ-based wavefront shaping [2].
Improving the transmittance of an epsilon-near-zero-based wavefront shaper
2016
Although Epsilon-Near-Zero metamaterials (ENZ) offer many unconventional ways to play with light, the optical impedance mismatch with surroundings can limit the efficiency of future devices. We report here on the improvement of the transmittance of an Epsilon-Near-Zero (ENZ) wavefront shaper. We first address in this paper the way to enhance the transmittance of a plane wave through a layer of ENZ material thanks to a numerical optimization approach based on the Transfer Matrix Method. We then transpose the one dimensional approach to a two dimensional case where the emission of a dipole is shaped into a plane wave by an ENZ device with a design that optimizes the transmittance. As a result…
Quasi-isoactinic reactor for photocatalytic kinetics studies
2007
Photochemical reactors characterized by almost uniform values of the local volumetric rate of photon absorption (LVRPA), i.e., quasi-isoactinic photoreactors, are particularly suitable for assessing the influence of radiant field intensity in kinetic studies. In this work, Monte Carlo simulations have been performed to obtain LVRPA values in a flat photoreactor irradiated on both sides. This configuration appears to be particularly suitable for obtaining quasi-isoactinic conditions. The influence of catalyst albedo and scattering phase function is assessed, and the conditions for obtaining iso-actinicity are discussed. Finally, these conditions are related to an easy-to-measure parameter, n…