Search results for "Refractometry"
showing 8 items of 48 documents
Through-focus response of multifocal intraocular lenses evaluated with a spatial light modulator
2012
A new testing technique based on the use of a liquid crystal spatial light modulator (SLM) is proposed to analyze the optical quality of multifocal intraocular lenses (MIOLs). Different vergences and decentrations of the incident beam can be programmed onto the SLM in order to record the point spread function (PSF) for different object positions. From these axial PSFs, the through-focus modulation transfer function is computed. Because there are no moving parts in the experimental setup, this method is fast and versatile to assess MIOLs. Experimental results confirm the potential of the proposed method.
Photonic fractional Fourier transformer with a single dispersive device
2013
In this work we used the temporal analog of spatial Fresnel diffraction to design a temporal fractional Fourier transformer with a single dispersive device, in this way avoiding the use of quadratic phase modulators. We demonstrate that a single dispersive passive device inherently provides the fractional Fourier transform of an incident optical pulse. The relationships linking the fractional Fourier transform order and scaling factor with the dispersion parameters are derived. We first provide some numerical results in order to prove the validity of our proposal, using a fiber Bragg grating as the dispersive device. Next, we experimentally demonstrate the feasibility of this proposal by us…
Back-scattering of whispering-gallery-modes resonances of cylindrical microcavities: Refractometric applications
2009
Whispering-gallery modes (WGM) resonances of microcapillaries are directly compatible with microfluidic systems and have demonstrated its suitability for refractometric applications [1]. Microcapillaries with a submicrometric wall exhibit very large wavelength shifts as a function of the refractive index of the liquids that fill the inside of the capillary [2]. The spatial separation between the surface where the total internal reflection takes place (the outer surface) and the sensing surface (the inner surface) where the wave interacts with the analyte is a unique property that can be exploited to deal with analytes with a refractive index higher than that of the capillary [2].
Refractometric sensor based on whispering-gallery modes of thin capillarie.
2009
Whispering-gallery modes resonances of submicron wall thickness capillaries exhibit very large wavelength shifts as a function of the refractive index of the medium that fills the inside. The sensitivity to refractive index changes is larger than in other optical microcavities as microspheres, microdisks and microrings. The outer surface where total internal reflection takes place remains always in air, enabling the measure of refractive index values higher than the refractive index of the capillary material. The fabrication of capillaries with submicron wall thickness has required the development of a specific technique. A refractometer with a response higher than 390 nm per refractive ind…
Refractive index and equilibrium water content of conventional and silicone hydrogel contact lenses
2006
Prova tipográfica (In Press)
Analysis of the angular acceptance of surface plasmon Bragg mirrors
2007
International audience; We analyze an important aspect of the behavior of surface plasmon polariton (SPP) Bragg mirrors: the dependence of the angular acceptance for reflection on the incidence angle. By means of leakage radiation microscopy, both in direct and Fourier space, we observe that the angular acceptance diminishes for increasing incidence angles. This effect, which can considerably affect the design of devices based on these elements, is shown to be the consequence of the decrease of the bandgap width with increasing incidence angle. (c) 2007 Optical Society of America.
Digitālās refrakcijas pielietojums labākā koriģētā redzes asuma novērtēšanai
2021
Darbs ir uzrakstīts angļu valodā uz 36 lappusēm, satur 20 attēlus, 4 tabulas un 35 literatūras avotus. Darba mērķis ir pārbaudīt redzes asumu ar trim refrakcijas metodēm: autorefraktometriju, subjektīvo refraktometriju un digitālo refraktometriju ar ierīci ESSILOR Vision R-800. Tika salīdzināta refrakcija 15 subjektiem vecumā no 12 līdz 40 gadiem. Refrakcijas dati tika pārveidoti optiskā stipruma vektora formā. Rezultāti: Statistiski nozīmīgas atšķirības tika konstatētas redzes asumam, bet ne optiskā stipruma vektoriem, kas bija ļoti līdzīgi viens otram. Secinājums: digitālā refrakcija ar precizitāti 0,01 D pie nepārtrauktas optiskā stipruma maiņas parādīja labāku redzes asumu pat pie zema …
Birefringent porous silicon membranes for optical sensing
2012
In this work anisotropic porous silicon is investigated as a material for optical sensing. Birefringence and sensitivity of the anisotropic porous silicon membranes are thoroughly studied in the framework of Bruggeman model which is extended to incorporate the influence of environment effects, such as silicon oxidation. The membranes were also characterized optically demonstrating sensitivity as high as 1245 nm/RIU at 1500 nm. This experimental value only agrees with the theory when it takes into consideration the effect of silicon oxidation. Furthermore we demonstrate that oxidized porous silicon membranes have optical parameters with long term stability. Finally, we developed a new model …