Electrical time resolved metrology of dust particles growing in low pressure cold plasmas

International audienceThe electrical parameters of a capacitively coupled radiofrequency (CCRF) discharge change significantly when dust arises in the discharge. This work demonstrates the ability to follow in real time the evolution of the size and of the concentration of dust particles forming in a CCRF discharge from the variation of the electron density and of the self-bias voltage of the active electrode. According to experimental findings, it appears that the variation of this self-bias voltage depends on the surface of the dust particles. This trend is confirmed by an analytical modelling considering the low frequency behaviour of the phenomenon

Modélisation des résonances Fano dans les structures périodiques métallo-diélectriques pour exciter les résonances de Fano

International audience<span style="left: 165.4px; top: 342.038px; font-size: 15px; font-family: serif; transform: scaleX(0.956111);"&gtNotre travail a porté sur l'étude et la modélisation des structures périodiques métallo</span&gt<span style="left: 691.405px; top: 342.038px; font-size: 15px; font-family: serif; transform: scaleX(0.972646);"&gt-diélectriques pouvant </span&gt<span style="left: 165.4px; top: 359.243px; font-size: 15px; font-family: serif; transform: scaleX(0.955462);"&gtsupporter des résonances Fano correspondant au couplage d'un mode de Bloch non radiatif avec une onde </span&gt<span style="left: 165.4px; top: 376.448px; font-size: 15px; font-family: serif; transform: scaleX(1.02312);"&gtplane incidente. Après avoir effectué un test de validation des codes de calcul utilisés, nous avons mené une </span&gt<span style="left: 165.4px; top: 393.653px; font-size: 15px; font-family: serif; transform: scaleX(0.947641);"&gtétude FDTD (calcul de bande et de diffraction</span&gt<span style="left: 452.605px; top: 393.653px; font-size: 15px; font-family: serif; transform: scaleX(0.967289);"&gt) montrant</span&gt<span style="left: 517px; top: 393.653px; font-size: 15px; font-family: serif; transform: scaleX(0.94997);"&gt l 'excitation des résonances Fano dans les cristaux </span&gt<span style="left: 165.4px; top: 411.053px; font-size: 15px; font-family: serif; transform: scaleX(1.00262);"&gtphotoniques.</span&g

Half-wave plate based on a birefringent metamaterial in the visible range

International audienceIn this paper, a half-wave plate (HWP) based on a birefringent metamaterial is numerically designed to operate in the visible range. The proposed structure consists of an array of double-pattern perpendicular rectangular apertures (RAA) engraved into opaque silver film deposited on a glass substrate. One of the apertures is glass filled. The operating principle is based on the excitation and the propagation of one guided mode inside each aperture but with different effective indices. After transmission, a phase difference is obtained between the two transverse components, which value depends mainly on the metal thickness. We have investigated the simplest configuration using a homemade code based on the finite difference time domain method to design a half-wave plate with optimized efficiency resulting in transmission coefficient of more than 60% together with a birefringence of 2.1 at an operation wavelength of 737nm.<span class="math"&gt<span class="MathJax_Preview" style=""&gt</span&gt<span style="font-size: 90%; display: inline-block; position: relative;" class="MathJax_SVG" id="MathJax-Element-1-Frame" tabindex="0" data-mathml="<math xmlns=&quot;http://www.w3.org/1998/Math/MathML&quot;&gt<mrow is=&quot;true&quot;&gt<mn is=&quot;true&quot;&gt737</mn&gt<mspace class=&quot;nbsp&quot; width=&quot;1em&quot; is=&quot;true&quot; /&gt<mi is=&quot;true&quot; mathvariant=&quot;normal&quot;&gtnm</mi&gt</mrow&gt</math&gt" role="presentation"&gt<svg xmlns:xlink="http://www.w3.org/1999/xlink" width="9.425ex" height="1.972ex" style="vertical-align: -0.25ex;" viewBox="0 -741.6 4058.2 849.3" aria-hidden="true"&gt<g stroke="currentColor" fill="currentColor" stroke-width="0" transform="matrix(1 0 0 -1 0 0)"&gt<g&gt<g&gt<use xlink:href="https://www.sciencedirect.com/science/article/abs/pii/S0030401821000547?via%3Dihub#MJMAIN-33" x="500" y="0"&gt</use&gt<use xlink:href="https://www.sciencedirect.com/science/article/abs/pii/S0030401821000547?via%3Dihub#MJMAIN-37" x="1001" y="0"&gt</use&gt</g&gt</g&gt</g&gt</svg&gt</span&gt</span&gtThis kind of anisotropic metasurfaces promises a wide range of applications in integrated photonics

Simulation of optical properties in photonic structures by the pseudo-spectral temporal domain method (PSTD)

International audienc

Conception par FDTD d’une lame demi onde dans la gamme optique à base de métamatériau biréfrignent

International audience<span style="left: 118.18px; top: 407.223px; font-size: 15px; font-family: serif; transform: scaleX(1.00097);"&gtDans ce travail, nous avons étudié un réseau périodique sublongueur d'onde composé de</span&gt<span style="left: 647.98px; top: 407.223px; font-size: 15px; font-family: serif; transform: scaleX(0.999398);"&gt deux ouvertures rectangulaire et </span&gt<span style="left: 118.18px; top: 424.623px; font-size: 15px; font-family: serif; transform: scaleX(0.997207);"&gtcoaxiale </span&gt<span style="left: 171.775px; top: 424.623px; font-size: 15px; font-family: serif; transform: scaleX(1.00172);"&gtgravées dans un film en argent</span&gt<span style="left: 355.57px; top: 424.623px; font-size: 15px; font-family: serif; transform: scaleX(1.004);"&gt dans le but de</span&gt<span style="left: 442.36px; top: 424.623px; font-size: 15px; font-family: serif; transform: scaleX(0.996076);"&gt concevoir des </span&gt<span style="left: 532.555px; top: 424.623px; font-size: 15px; font-family: serif; transform: scaleX(0.98822);"&gtlames</span&gt<span style="left: 567.355px; top: 424.623px; font-size: 15px; font-family: serif; transform: scaleX(1.00095);"&gt biréfringentes dans le domaine optique. Cette </span&gt<span style="left: 118.15px; top: 441.828px; font-size: 15px; font-family: serif; transform: scaleX(1.00034);"&gtétude a été réalis</span&gt<span style="left: 218.545px; top: 441.828px; font-size: 15px; font-family: serif; transform: scaleX(0.994135);"&gtée </span&gt<span style="left: 235.54px; top: 441.828px; font-size: 15px; font-family: serif; transform: scaleX(1.00043);"&gtà l'aide d'un code maison FDTD où la dispersion du métal est décrite par le modèl</span&gt<span style="left: 727.135px; top: 441.828px; font-size: 15px; font-family: serif; transform: scaleX(1.006);"&gte de Drude</span&gt<span style="left: 793.135px; top: 441.828px; font-size: 15px; font-family: serif; transform: scaleX(0.997938);"&gt à deux </span&gt<span style="left: 118.135px; top: 459.033px; font-size: 15px; font-family: serif; transform: scaleX(1.00025);"&gtpoints critiques (DCP). La particularité du mode TEM de la cavité coaxiale, qui peut être excité à des longueurs d'onde él</span&gt<span style="left: 846.73px; top: 459.033px; font-size: 15px; font-family: serif; transform: scaleX(0.990129);"&gte-</span&gt<span style="left: 118.135px; top: 476.238px; font-size: 15px; font-family: serif; transform: scaleX(1.00027);"&gtvées, a permis de concevoir une plaque demi</span&gt<span style="left: 387.13px; top: 476.238px; font-size: 15px; font-family: serif; transform: scaleX(1.00686);"&gt-onde </span&gt<span style="left: 425.125px; top: 476.238px; font-size: 15px; font-family: serif; transform: scaleX(1.0009);"&gtdans le domaine optique</span&g

Etude et modélisation d'un guide ridge avec réseau de Bragg de faible largeur en niobate de lithium

International audience<span style="left: 66.0375px; top: 181.588px; font-size: 7.94962px; font-family: serif; transform: scaleX(0.998696);"&gt</span&gt<span style="left: 77.485px; top: 181.588px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.01757);"&gtCe travail est consacré à l’étude d’un guide ridge en </span&gt<span style="left: 41.338px; top: 190.913px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.06906);"&gtniobate de lithium (LiNbO</span&gt<span style="left: 139.065px; top: 193.701px; font-size: 5.29975px; font-family: serif;"&gt3</span&gt<span style="left: 142.245px; top: 190.915px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.09143);"&gt) pouvant supporter un réseau de </span&gt<span style="left: 41.3407px; top: 200.034px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.04435);"&gtBragg. Cette étude est réalisée par simulation FDTD. Nous avons </span&gt<span style="left: 41.3407px; top: 209.152px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.03063);"&gtcommencé par l’adaptation et à l’intégration du modèle de </span&gt<span style="left: 41.3407px; top: 218.373px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.09949);"&gtSellmeier qui permet de décrire la dispersion du niobate de </span&gt<span style="left: 41.3407px; top: 227.492px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.03407);"&gtlithium dans la gamme optique. La présence d’un gradient </span&gt<span style="left: 41.3407px; top: 236.61px; font-size: 7.94962px; font-family: serif; transform: scaleX(0.992735);"&gtd’indice, induit par la diffusion de titane, est pris</span&gt<span style="left: 210.93px; top: 236.61px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.10936);"&gte en compte par </span&gt<span style="left: 41.3407px; top: 245.728px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.01077);"&gtl’introduction d’un terme additif dans l’expression de l’indice de </span&gt<span style="left: 41.3407px; top: 254.95px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.08881);"&gtréfraction. Après validation de notre code, nous avons réalisé des </span&gt<span style="left: 41.3407px; top: 264.068px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.01989);"&gtcalculs de diffraction. Nous avons ainsi montré qu’un réseau de </span&gt<span style="left: 41.3407px; top: 273.186px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.03332);"&gtBragg constitué de seulement trois alterna</span&gt<span style="left: 189.736px; top: 273.186px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.03682);"&gtnces permet d’obtenir </span&gt<span style="left: 41.3407px; top: 282.304px; font-size: 7.94962px; font-family: serif; transform: scaleX(1.04726);"&gtun coefficient de réflexion de 98%.</span&gt<span style="left: 120.622px; top: 299.229px; font-size: 8.79758px; font-family: serif; transform: scaleX(1.01451);"&gt</span&g

Fano Resonance in photonic crystal: temperature sensor application

International audience<span style="left: 252.494px; top: 338.654px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.892204);"&gtthe present study deals with the temperature sensitivity of 1D</span&gt<span style="left: 745.412px; top: 338.654px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.918073);"&gt periodic </span&gt<span style="left: 177.9px; top: 359.851px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.975149);"&gtphotonic structure. This sensitivity is expressed by the displacement of</span&gt<span style="left: 745.927px; top: 359.851px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.932875);"&gtthe Fano </span&gt<span style="left: 177.9px; top: 380.845px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.941352);"&gtresonance wavelength observed on the transmission spectra. The studied s</span&gt<span style="left: 756.939px; top: 380.845px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.913137);"&gttructure </span&gt<span style="left: 177.9px; top: 402.042px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.972093);"&gtconsists of a periodic arrangement of silver pattern on a Niobate lithium (</span&gt<span style="left: 752.082px; top: 402.042px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.954754);"&gtLiNbO</span&gt<span style="left: 801.902px; top: 409.713px; font-size: 11.6px; font-family: sans-serif;"&gt3</span&gt<span style="left: 807.702px; top: 402.054px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.978601);"&gt) </span&gt<span style="left: 177.906px; top: 423.048px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.928768);"&gtsubstrate. Due to the pyroelectric effect of</span&gt<span style="left: 499.299px; top: 423.048px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.95807);"&gtLiNbO</span&gt<span style="left: 549.301px; top: 430.713px; font-size: 11.6px; font-family: sans-serif;"&gt3</span&gt<span style="left: 555.101px; top: 423.054px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.895466);"&gt, the temperature changes induce a </span&gt<span style="left: 177.901px; top: 444.048px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.952288);"&gtsensitive variation of its refractive index. The obtained resul</span&gt<span style="left: 637.099px; top: 444.048px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.96496);"&gtts show a sensitivity of </span&gt<span style="left: 177.901px; top: 465.648px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(0.89231);"&gtabout </span&gt<span style="left: 223.294px; top: 464.561px; font-size: 18.4px; font-family: sans-serif; transform: scaleX(1.35992);"&gtܥ°/݉݊ 0.77</span&gt<span style="left: 315.294px; top: 465.648px; font-size: 18.4px; font-family: sans-serif;"&gt.</span&g

On-Ground measurement of dust residual charge in a dusty plasma afterglow using thermophoretic gravity compensation

Dusty or complex plasmas are partially ionized gas composed of neutral species, ions, electrons, and charged dust particles. In laboratory experiments, these particles can be either injected or grown directly in the plasma. Injected dust particles are usually micron-size particles. Due to their mass, they are confined near the bottom electrode where the electric force counterbalances gravity. The microgravity condition is necessary to study dust clouds of micrometer-size particles filling the whole plasma chamber. In the laboratory, dense clouds of submicron particles light enough to completely fill the gap between the electrodes can be obtained using reactive gases such as silane or using a target sputtered with ions from plasma. Dust-particle charge is a key parameter in complex plasma. It determines the interaction between a dust particle and electrons, ions, its neighboring dust particles, and electric field. However there are only a few papers devoted to dust charging, or decharging to be more specific, in the discharge afterglow. In this paper, we report an on-ground experiment on the residual charge measurement of dust particles after the decay of a dusty plasma. The experiment was performed in the PKE-Nefedov reactor where the dust particles were physically grown in the plasma. A temperature gradient was introduced in the chamber to create an upward thermophoretic force to balance gravity in order to maintain the dust particles in the volume of the chamber when the discharge is switched off. The residual charges were determined from an analysis of dust oscillations, which were excited by applying a sinusoidal bias to the bottom electrode. It was shown that dust particles do keep a residual charge of few electrons and that both positively and negatively charged dust particles coexist in the late plasma afterglow. In order to understand these results, measurements on electron density decay have been performed into other dusty discharges such as argon/methane dilution plasma and sputtering discharge