Search results for "Optical"

Properties of silicon integrated photonic lenses: bandwidth, chromatic aberration, and polarization dependence

2013

We analyze the properties of silicon integrated photonic lenses based on scattering optical elements. The devices have been inverse- designed by combining genetic algorithms and the multiple scattering theory. These lenses are able to focus an infrared plane wave front on a position freely determined during the design stage. The nanofabricated silicon integrated lenses have proved effective over a large range of wave- lengths, measured to be of the order of 100 nm. The lenses show chromatic aberration, with a displacement of the position of the focus mea- sured to be higher than 1.5 μm when the wavelength varies from 1500 to 1600 nm. Moreover, we analyze the polarization of the focused beam…

Optical phase retrieval using four rotated versions of a single binary amplitude modulating mask

2019

In recent years, phase retrieval methods recovering the phase of an object from coded diffraction patterns have gained popularity. A numerical phase retrieval method called PhaseLift that recovers the phase of an object from a very limited number of coded diffraction patterns was recently proposed. Performance of PhaseLift has been analyzed for different types and the number of masks modulating an object. We present a unique application of PhaseLift that uses four rotations of a single mask, modulating only the amplitude of an object. In simulations, a phase screen with the root-mean-square (RMS) value 0.294  μm was used as the test object. The RMS value of the retrieved phase screen after …

Tolerance to rotation of toric monofocal and bifocal intraocular lenses. A theoretical study

2018

Abstract This manuscript aims to evaluate the tolerance to rotation of a toric monofocal and a toric bifocal intraocular lenses with different cylinder powers. Theoretical designs based on wavefront aberrations were created to simulate a toric monofocal and a toric bifocal intraocular lens. Cylinder power ranged from −1 D to −6 D, in steps of −1 D. Tolerance to rotation was estimated by the visual Strehl ratio based on the optical transfer function (VSOTF) metric. Tolerance to rotation for both monofocal and bifocal intraocular lenses decreased when the cylinder power increased. For the bifocal design studied, the tolerance to rotation was larger for the near focus than for the far, however…

Drifts in real-time partial wavefront correction and how to avoid them

2017

In visual experiments that require real-time partial correction of wavefront aberrations, small errors occur that accumulate over time and lead to drifts in Zernike coefficients of the uncorrected aberrations. A simple algorithm that does not require the inclusion of an additional optical path to obtain independent measurements of the eye's aberrations is described here, and its effectiveness in preventing these drifts is demonstrated.

The tear film and the optical quality of the eye

2010

The stability of the tear film plays an important role in the optical quality of the eye. Various methods have been developed to quantify the contribution of the tear film to optical quality, including the double-pass optical method, Hartmann-Shack wavefront sensing, videokeratoscopy, retroillumination analysis, and interferometry. In addition to assessing the effect of tear film irregularities, these methods can aid in the diagnosis of dry-eye related conditions and the monitoring of therapy. This review describes the methodologies used to assess the relationship between the tear film and optical quality of the eye and summarizes the most important findings obtained with these methods with…

Modeling propagation for high-power cylindrical microwave applicators

2001

In this letter, the dispersion characteristics and energy configurations of a cylindrical partially filled waveguide or lossy multilayered rod shielded by a metallic enclosure are presented for several modes. These parameters are obtained by a numerical simulation based on the residues theory. © 2001 John Wiley & Sons, Inc. Microwave Opt Technol Lett 30: 192–195, 2001.

Performance of electro-optical plasmonic ring resonators at telecom wavelengths

2012

International audience; In this work we report on the characteristics of an electro-optical dielectric-loaded surface plasmon polariton waveguide ring resonator. By doping the dielectric host matrix with an electro-optical material and designing an appropriate set of planar electrodes, we measured a 16% relative change of transmission upon application of a controlled electric field. We have analyzed the temporal response of the device and conclude that electrostriction of the host matrix is playing a dominating role in the transmission response.

Efficient excitation of dielectric-loaded surface plasmon-polariton waveguide modes at telecommunication wavelengths

2008

International audience; The excitation of surface plasmon-polariton (SPP) waveguide modes in subwavelength dielectric ridges deposited on a thin gold film has been characterized and optimized at telecommunication wavelengths. The experimental data on the electromagnetic mode structure obtained using scanning near-field optical microscopy have been directly compared to full vectorial three-dimensional finite element method simulations. Two excitation geometries have been investigated where SPPs are excited outside or inside the dielectric tapered region adjoint to the waveguide. The dependence of the efficiency of the SPP guided mode excitation on the taper opening angle has been measured an…

FDTD signal extrapolation using a finite impulse response neural network model

1999

Modelling of Laser Operation in RPE Nd3+:LiNbO3 Channel Waveguides

2006

In this work, laser action in RPE Nd3+:LiNbO3 is modelled by using the overlapping integrals method. Different pumping schemes, TE or TM, have been considered in order to reproduce the experimental measurements. Calculated results indicate that the slope efficiency remains basically independent on the pumping scheme while the threshold pump power increases for TE pumping.