Search results for "Refractive"
showing 10 items of 559 documents
Broadband tuning of polarization modulation instability in microstructured optical fibers
2020
The wideband tuning of strong bands generated through polarization modulation instability (PMI) in microstructured optical fibers (MOFs) is reported. Tunability is achieved by exploiting the dependence of the phase-matching condition on the fiber’s chromatic dispersion and birefringence, which is particularly sensitive when the fiber is pumped near the zero-dispersion wavelength. MOFs designed to accomplish PMI phase-matching when they are infiltrated with ethanol and pumped at 1064 nm were designed and fabricated. Taking advantage of the large thermo-optic coefficient of ethanol, both chromatic dispersion and birefringence were varied through temperature. Wavelength shifts from 937 nm to 8…
Plasmonics co-integrated with silicon nitride photonics for high-sensitivity interferometric biosensing
2019
We demonstrate a photonic integrated Mach-Zehnder interferometric sensor, utilizing a plasmonic stripe waveguide in the sensing branch and a photonic variable optical attenuator and a phase shifter in the reference arm to optimize the interferometer operation. The plasmonic sensor is used to detect changes in the refractive index of the surrounding medium exploiting the accumulated phase change of the propagating Surface-Plasmon-Polariton (SPP) mode that is fully exposed in an aqueous buffer solution. The variable optical attenuation stage is incorporated in the reference Si3N4 branch, as the means to counter-balance the optical losses introduced by the plasmonic branch and optimize interfe…
Refractive micro-optical elements for surface plasmons: from classical to gradient index optics.
2010
Controlling the propagation of surface plasmons along a metal-dielectric interface is a key feature for the development of surface plasmon based circuits. We have designed various two-dimensional refractive dielectric optical elements for surface plasmons (SP) and characterized their capacity to route SP, using near- or far-field techniques. We first present basic devices analogous to usual optical components and the associated challenges for SP optics. We then use a metamaterial approach to locally vary the refractive index and fabricate gradient index structures for SP circuitry.
Whispering Gallery Mode Resonator Temperature Compensation and Refractive Index Sensing in Glucose Droplets.
2021
Among the different types of photonic sensor devices, optical whispering gallery mode resonators (WGMRs) have attracted interest due to their high level of sensitivity, small size, and ability to perform real-time temperature measurements. Here we demonstrate the applicability of temperature measurements using WGMR in both air and liquid environments. We also show that WGMR allowed measurements of the refractive index variations in an evaporating glucose–water solution droplet. The thermal tuning of WGMR can be reduced by coating WGMRs with a thin layer of polymethyl methacrylate (PMMA). Dip-coating the silica microsphere multiple times significantly reduced the resonance shift, partially c…
Optical Quality Comparison of Conventional and Hole-Visian Implantable Collamer Lens at Different Degrees of Decentering
2012
To compare the optical quality of implantable Collamer lens (ICL) with and without central hole (Hole ICL and conventional ICL) at different degrees of decentering.Experimental laboratory investigation.Wavefront aberrations of the -3, -6, and -12 diopter (D) V4b and -3, -6, and -12 D V4c ICLs were measured in 3 conditions-centered and decentered 0.3 and 0.6 mm-at 3-mm and 4.5-mm pupils. The root mean square of total higher order aberrations, trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were evaluated. In addition, point spread function and simulated retinal images of ICLs were calculated from the wavefront aberrations for each ICL and all conditions of decenteri…
Predictability of intraocular lens power calculation after small-incision lenticule extraction for myopia
2019
PURPOSE To evaluate and compare the predictability of intraocular lens (IOL) power calculation after small-incision lenticule extraction (SMILE) for myopia and myopic astigmatism. SETTING Department of Ophthalmology, Philipps University of Marburg, Marburg, Germany. DESIGN Retrospective comparative case series. METHODS Preoperative evaluation included optical biometry using IOLMaster 500 and corneal tomography using Pentacam HR. The corneal tomography measurements were repeated at 3 months postoperatively. The change of spherical equivalent due to SMILE was calculated by the manifest refraction at corneal plane (SMILE-Dif). A theoretical model, involving the virtual implantation of the same…
Lateral magnification matrix from the dioptric power matrix formalism in the paraxial case.
2012
Background Previous studies have highlighted that power matrices fully characterize the concept of dioptric power of any astigmatic surface. Thus, the basic equations in physiological optics can be generalized using the matrix formalism of the dioptric power. Among others, lateral magnification has also been interpreted as a matrix but mainly concerning magnification modification induced by spectacle correction of refractive error. Purpose To provide a fresh look into a novel paraxial formulation for the assessment of the lateral magnification using power matrices and in presence of astigmatism for thin and thick imaging systems in general. Methods Linear optics provides the frame to genera…
Spatial information transmission using axial temporal coherence coding
2007
We present an approach that can be used for transmission of information through space-limited systems or for superresolution. The spatial information is coded with different axial temporal coherence by interfering every spatial region in the input with the same region, but with a certain known delay in the longitudinal axis. Every spatial region has different delay. After mixing all of the spatial information, it is transmitted through the space-limited system. At the detection the information is passed through a similar interference setup containing certain axial delay. By temporally scanning along the longitudinal axis, each time a different spatial region that was coded with the correspo…
Uniform fibre Bragg gratings with an embedded perturbed section for multiple applications
1999
The interest in fibre Bragg gratings has been increased with the development of flexible fabrication techniques which are able to make gratings with any non-uniform characteristic (chirped, apodised, sampled, phase-shifted, etc.) required for an specific application [1].
<title>Bragg and asymmetric-relief reflection gratings in As-S-Se thin films</title>
2005
Bragg and asymmetric-relief gratings and their formation in the amorphous As-S-Se films are discussed. Due to the high refractive index and its photoinduced change, the films are useful in holography. The thickness of the As0.4S0.15Se0.45 and As0.4S0.3Se0.3 films used in the Bragg gratings is optimized. The dependence of the dimaction efficiency of the asymmetric-relief gratings on the conditions of recording, chemical treating, and reading out (polarization and angle) is studied.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.