Search results for "photonics"

Observation of elastic anisotropy in strained optical nanofibers using Brillouin spectroscopy

2019

Optical nanofibers (ONFs) are excellent nanophotonic platforms for many applications such as optical sensing, quantum photonics, and nonlinear optics, due to both tight optical confinement and their evanescent field. From an acoustic viewpoint, it has recently been reported the observation of a new class of Brillouin acoustic resonances in optical nanofibers, including hybrid shear/longitudinal acoustic waves (HAWs) and surface acoustic waves (SAWs) [1–2]. It has been later shown that, under axial tensile strain, the Brillouin frequency shifts (BFS) of these elastic resonances are fundamentally different from that of standard optical fibers [3]. This is principally due to the hybrid nature …

Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber

2009

Nonlinear femtosecond pulse propagation in an all-solid photonic bandgap fiber is experimentally and numerically investigated. Guiding light in such fiber occurs via two mechanisms: photonic bandgap in the central silica core or total internal reflection in the germanium doped inclusions. By properly combining spectral filtering, dispersion tailoring and pump coupling into the fiber modes, we experimentally demonstrate efficient supercontinuum generation with controllable spectral bandwidth.

Angular Trapping of Anisometric Nano-Objects in a Fluid

2012

We demonstrate the ability to trap, levitate, and orient single anisometric nanoscale objects with high angular precision in a fluid. An electrostatic fluidic trap confines a spherical object at a spatial location defined by the minimum of the electrostatic system free energy. For an anisometric object and a potential well lacking angular symmetry, the system free energy can further strongly depend on the object's orientation in the trap. Engineering the morphology of the trap thus enables precise spatial and angular confinement of a single levitating nano-object, and the process can be massively parallelized. Since the physics of the trap depends strongly on the surface charge of the objec…

Steam sterilization processes affect the stability of clinical thermometers: Thermistor and prototypal FBG probe comparison

2020

Abstract Temperature is one of the most frequently measured physical quantities in clinical environment and a good biomarker of illness. The need for reusable probes, which have to be sterilized to prevent infections, requires the metrological qualification of thermometer probes in response to ageing effects induced by several sterilization processes. In this study, we investigated the effect of repeated sterilizations on both a commonly-used autoclavable thermistor probe and a prototypal Fiber Bragg Gratings (FBG) probe for temperature measurements. Findings highlighted a greater reliability of the proposed FBG probe than the commercial thermistor. Specifically, the FBG probe was able to w…

Surface plasmon-polariton amplifiers

2012

Propagation of surface plasmons at metal surfaces is receiving much interest nowadays because of its broad range of potential applications, like subwavelength photonics or biosensing. Although plasmonic devices achieve unique properties, surface plasmons suffer from high attenuation because of the absorption losses in the metal. This limitation can be overcome by providing the material adjacent to the metal with optical gain. Under these conditions, absorption losses are compensated and the propagation length of the plasmon is significantly increased. In this work, a review of plasmonic amplifiers is presented. To this end, the state of the art of such devices and the propagation characteri…

Myopia, the challenge of Ophthalmology and its worldwide “explosive epidemic”

2018

Visual quality comparison of conventional and Hole-Visian implantable collamer lens at different degrees of decentering

2013

Purpose To compare the visual quality of implantable collamer lens (ICL) with and without central hole (Hole ICL and conventional ICL) at different degrees of decentering. Methods An adaptive optics visual simulator (crx1, Imagine Eyes, Orsay, France) was used to simulate the –3, –6 and –12 dioptres (D) conventional and Hole ICLs in three conditions: centred and decentred 0.3 and 0.6 mm. Visual acuity (VA) at high-contrast, medium-contrast and low-contrast and contrast sensitivity (CS) were measured in 15 observers for 3 and 4.5 mm pupils. Results No statistically significant differences in VA and CS were found between conventional and Hole ICLs for any ICL powers and pupil sizes evaluated …

Optical and Visual Simulation of Standard and Modified Spherical Aberration Implantable Collamer Lens Post Myopic LASIK Surgery

2013

To evaluate the visual quality achieved in patients undergoing standard or modified implantable Collamer lens (ICL) to correct residual myopic error after laser-assisted in situ keratomileusis (LASIK) surgery.The adaptive optics visual simulator was used to simulate LASIK surgery of moderate and high myopia with a myopic regression corrected by a standard and modified ICL. Visual acuity (VA) and contrast sensitivity (CS) were measured in 14 subjects at 3- and 4.5-mm pupil. Point spread function and simulated retinal images were calculated.Comparing LASIK plus standard ICL and LASIK plus modified ICL simulations, for moderate myopia, VA improvement was less than 1 line in all VA contrasts an…

Image quality and visual performance in the peripheral visual field following photorefractive keratectomy.

2002

ABSTRACT PURPOSE: A theoretical and experimental study was performed to assess the possible effects of photorefractive keratectomy (PRK) on retinal image quality and thresholds in the peripheral visual field. METHODS: Simple optical calculations suggest that although the quality of the retinal image at the fovea of the postoperative PRK eye may be comparable to that in an emmetropic eye, images in the peripheral field may be markedly worse, since peripheral ray bundles may pass partly through ablated and partly through unablated cornea, giving a simultaneous-vision bifocal effect. This would be expected to create an annular zone of confusion, so that light from two different directions in o…

A Passive-Marker-Based Optical System for Computer-Aided Surgery in Otorhinolaryngology: Development and First Clinical Experiences

1999

Objectives: To develop a new type of optical computer-aided surgery (CAS) device that overcomes some of the restrictions of common systems and to examine its accuracy and usability under laboratory and intraoperative conditions. Study Design: Prospective study using laboratory experiments and intraoperative data collection. Methods: An optical CAS system applying passive optical markers for coordinate determination was developed. Laboratory accuracy measurements were obtained on a Plexiglas model with known coordinates of fiducial markers, before and after predefined table movements. Intraoperative accuracy measurements were recorded from 24 patients undergoing endonasal surgery of the para…