Search results for "OPTICS"
showing 10 items of 10033 documents
Extensive tailorability of sound absorption using acoustic metamaterials
2017
We present an experimental demonstration of sound absorption tailorability, using acoustic metamaterials made of resonant cavities that does not rely on any dissipative material. As confirmed by numerical calculation, we particularly show that using quarter-wave-like resonators made of deep subwavelength slits allows a high confinement of the acoustic energy of an incident wave. This leads to enhance the dissipation in the cavities and, consequently, generates strong sound absorption, even over a wide frequency band. We finally demonstrate experimentally the key role of the filling ratio in tailoring such an absorption, using a metamaterial constituted of space-coiled cavities embedded in a…
Single crystal EXAFS at high pressure
2000
Abstract We present a new technique for structure characterization under high pressure conditions. The use of an undulator beam of the third-generation ESRF source of synchrotron radiation has enabled the first single crystal EXAFS experiments at high pressure using a diamond anvil cell as pressure generator. Taking advantage of the linear polarization of X-rays the technique becomes an orientation-selective probe of the local structure of materials. We describe the principle of the technique and some applications.
Optical force rectifiers based on PT-symmetric metasurfaces
2018
We introduce here the concept of optical force rectifier based on parity-time symmetric metasurfaces. Directly linked to the properties of non-Hermitian systems engineered by balanced loss and gain constituents, we show that light can exert asymmetric pulling or pushing forces on metasurfaces depending on the direction of the impinging light. This generates a complete force rectification in the vicinity of the exceptional point. Our findings have the potential to spark the design of applications in optical manipulation where the forces, strictly speaking, act unidirectionally. R.A. and B.G. would like to acknowledge financial support from the Max Planck Society. J.C. acknowledges the suppor…
Entangled photons through thick scattering media: experiments and comparison with simulations of the biphoton wave function
2021
International audience; We report experimentally and numerically quantum correlations imaging through thick random media. We demonstrated that spatial correlations between twin photon are still detected but no in form of two-photon speckle-like patterns.
Tungsten oxide thin films sputter deposited by the reactive gas pulsing process for the dodecane detection
2015
International audience; The DC reactive magnetron sputtering of a metallic tungsten target was performed in an argon + oxygen atmosphere for depositing tungsten oxide thin films. In order to control the oxygen concentration in the films, the reactive gas pulsing process, namely RGPP, was implemented. Rectangular pulses were used with a constant pulsing period T = 16 s whereas the duty cycle α (time of oxygen injection to pulsing period T ratio) was systematically changed from 0 to 100% of T. This pulsing injection of the reactive gas allowed a gradual evolution of the films composition from pure metallic to over-stoichiometric WO3+ɛ’ compounds. These WOx films were sputter deposited on comm…
High Order modes in Cavity Resonator Integrated Guided mode resonance Filters (CRIGFs)
2015
International audience
Acoustic Topological Circuitry in Square and Rectangular Phononic Crystals
2021
International audience; We systematically engineer a series of square and rectangular phononic crystals to create experimental realizations of complex topological phononic circuits. The exotic topological transport observed is wholly reliant upon the underlying structure which must belong to either a square or rectangular lattice system and not to any hexagonal-based structure. The phononic system chosen consists of a periodic array of square steel bars which partitions acoustic waves in water over a broadband range of frequencies (∼0.5MHz). An ultrasonic transducer launches an acoustic pulse which propagates along a domain wall, before encountering a nodal point, from which the acoustic si…
Target 5G visible light positioning signal subcarrier extraction method using particle swarm optimization algorithm
2021
International audience; With the explosive growth of demand for Internet of Things (IoT) applications and the increasing dependence of users on wireless connections, indoor location based service(LBS) under 5G-Public-Private Partnership (5G-PPP) using cases have received more attention and get rapid development. Thanks to the safty, security and customization of 5G network pointed by 5G forum white paper, indoor positioning systems using unified 5G New Radio (NR) signals have become the focus of the next generation of visible light positioning (VLP) systems. In 5G New Radio(NR) frame, totally 192 subcarriers are used to carry positioning reference signal(PRS). In order to improve the positi…
Caractérisation d'une fibre optique ultra non-linéaire en verre de chalcogénure
2009
session orale 3 « Effets nonlinéaires » [Ma1.4], http://optiquelille2009.univ-lille1.fr/; National audience; Nous présentons les résultats expérimentaux concernant la caractérisation d'une fibre optique microstructurée en verre de chalcogénure de composition AsSe. Ces mesures concernent l'atténuation, la dispersion, l'aire effective et le coefficient non-linéaire du troisième ordre. Cette fibre présente un fort potentiel pour des applications non-linéaires avec un coefficient non-linéaire Kerr de 15 400 W-1m-1.
Surface plasmon interference excited by tightly focused laser beams
2007
International audience; We show that interfering surface plasmon polaritons can be excited with a focused laser beam at normal incidence to a plane metal film. No protrusions or holes are needed in this excitation scheme. Depending on the axial position of the focus, the intensity distribution on the metal surface is either dominated by interferences between counterpropagating plasmons or by a two-lobe pattern characteristic of localized surface plasmon excitation. Our experiments can be accurately explained by use of the angular spectrum representation and provide a simple means for locally exciting standing surface plasmon polaritons.