Search results for "Photonics"

Current modulation induced stability in laser diode under high optical feedback strength

2021

The back-reflection of emitted laser beam (optical feedback, also know as selfmixing) from various external interfaces are sufficient to cause instability, and prohibiting its use in various fields such as communication, spectroscopy, imaging to name a few. So it is desirable to study the laser dynamics and the conditions causing it to be stable in spite of strong optical feedback. With the aid of mathematical formulation, simulation and backed by experimental evidences, it is demonstrated that the frequency deviation of the laser emission due to current (intensity) modulation alters the dynamic state and boundary conditions of the system such that even under large optical feedback strength…

Integrated Optical Technique for Detection of Electro-Optical Non-Linearities in Thin Films

1976

A simple method for detection of electro-optical non-linearities in thin films is presented. The method involves an easily fabricated structure and a little practice in integrated optical techniques. It is also possible to detect small induced variations of refractive index, using lower voltage with respect to those applied in a conventional Kerr cell. We have sucessfully tested our method using two different polymer materials as thin films. In both of these we have observed an induced ?n ? 3 10?5 with an electric field of 60 V/?, with a response time round about 300 nsec. The experimental values of induced ?n versus electric field fit very well a parabola, proving the quadratic behavior of…

Incoherent solitons and condensation processes

2006

International audience; We study the nonlinear interaction of partially incoherent nonlinear optical waves. We show that, in spite of the incoherence of the waves, coherent phase effects may play a relevant role during the propagation, in contrast with the usual wave turbulence description of the interaction. These nonlinear phase effects may lead the system to unexpected processes of self-organization, such as condensation, or incoherent soliton generation in instantaneous response nonlinear media. Such self-organization processes may be characterized by a reduction of the non-equilibrium entropy, which violates the Boltzmann's H-theorem of entropy growth inherent to the wave turbulence th…

Applications in nanophotonics of lead halide perovskite nanocrystals

2021

Effect of Decentration on the Optical Quality of Two Intraocular Lenses

2016

To analyze the effect of decentration on the optical quality of two diffractive-refractive intraocular lenses, a bifocal and a trifocal, when displaced laterally (horizontal direction) from the center.The AT LISA 809M IOL (+3.75 D add) with two main foci and the AT LISA tri 839MP intraocular lens with three main foci (Carl Zeiss Meditec AG, Jena, Germany) were analyzed. The optical quality of the intraocular lenses was measured with the PMTF (power and modulation transfer function [MTF] measurement for refractive and diffractive intraocular lenses) optical bench (Lambda-X, Nivelles, Belgium). The optical quality of the lenses was evaluated by the MTF at different object vergences, the avera…

Optical Quality Comparison between Spherical and Aspheric Toric Intraocular Lenses

2014

Purpose To measure and compare the optical quality of spherical and aspheric toric intraocular lenses (IOLs). Methods Wavefront aberrations of AcrySof Toric and IQ Toric IOLs (Alcon Laboratories) for different powers were measured at 3- and 5-mm pupils by Nimo TR0805 instrument. The Zernike coefficients of trefoil, coma, tetrafoil, secondary astigmatism, and spherical aberration were evaluated. The point spread functions (PSFs) of each IOL evaluated were calculated from the wavefront aberrations. The PSF images also were calculated from the IOL wavefront aberrations, adding the cornea's aberrations to simulate the optical quality after their implantation. Results Spherical toric IOLs showed…

A rapid method for measuring intraocular lens power in vitro with a focimeter.

2015

In this paper we describe a new method for measuring the intraocular lens (IOL) power using a focimeter, a negative ophthalmic lens and a saline solution (0.9% NaCl). To test this we measured the power of 58 different IOLs and we compared them with the power stated by the manufacturer. Despite the limitations, the results show a good correlation.

Manipulating and squeezing the photon local density of states with plasmonic nanoparticle networks

2010

International audience; In this Brief Report, we show that when interconnected networks of gold particles are deposited onto a clean planar surface, they strongly modify the photonic local density of states LDOS in the immediate proximity of the self-assembled nanoparticles. They represent unique architectures for the subwavelength patterning of initially flat photonic LDOS. Moreover, we show that their local spectral signatures are well suited for the generation of sites able to enhance molecular fluorescence intensity.

WAVEFRONT TESTER: Un nuevo laboratorio virtual para el estudio de los sensores frente de onda.

2016

[EN] We present a new virtual laboratory developed with MatlabcGUI (Graphical User Interface) used toteach di erent aberration eff ects in the "Tecnologi a de Sensores Optoelectr onicos" at "Escuela T ecnicaSuperior de Ingenier a del Diseño" of the Universitat Polit ecnica de Val encia. The objective of this lab is to provide a computer tool to study the working principle of a Shack Hartman sensor and the parameters that determine the dynamic range of the same. Some examples made with di fferent aberrations (defocus,astigmatism, coma) and for diff erent sensor con gurations are presented.

Magnetism and Molecular Nonlinear Optical Second-Order Response Meet in a Spin Crossover Complex

2012

International audience; The quadratic hyperpolarizability of two inorganic Schiff base metal complexes which differ from each other by the nature of the central metal ion (FeII or ZnII) is estimated using hyper-Rayleigh light-scattering (HRS) measurements. The investigated FeII microcrystals exhibit a thermal spin-crossover (SCO) from a diamagnetic to a paramagnetic state centered at T1/2 = 233 K that can be reproduced by the HRS signal whose modest intensity is mainly due to their centrosymmetric packing structure. Diamagnetic ZnII microcrystals even lead to much weaker (∼400 times) HRS intensities which are in addition temperature-independent. These observations allow us to ascribe the ch…