Optomécanique dans les résonateurs intégrés et hybrides à cristal photonique bi-dimensionel

Optomechanical systems, in which the vibrations of a mechanical resonator are coupled to an electromagnetic radiation, have permitted the investigation of a wealth of novel physical effects. To fully exploit these phenomena in realistic circuits and to achieve different functionalities on a single chip, the integration of optomechanical resonators is mandatory. Here, we propose a novel approach to heterogeneously integrated arrays of two-dimensional photonic crystal defect cavities on top of silicon-on-insulator waveguides. The optomechanical response of these devices is investigated and evidences an optomechanical coupling involving both dispersive and dissipative mechanisms. By controlling optical coupling between the waveguide and the photonic crystal, we were able to vary and understand the relative strength of these couplings. This scalable platform allows for unprecedented control on the optomechanical coupling mechanisms, with a potential benefit in cooling experiments, and for the development of multi-element optomechanical circuits in the frame of optomechanically-driven signal-processing applications.Les systèmes optomécaniques, dans lesquels les vibrations d'un résonateur mécanique sont couplées à un rayonnement électromagnétique, ont permis l'examen de multiples nouveaux effets physiques. Afin d'exploiter pleinement ces phénomènes dans des circuits réalistes et d'obtenir différentes fonctionnalités sur une seule puce, l'intégration des résonateurs optomécaniques est obligatoire. Ici nous proposons une nouvelle approche pour la réalisation de systèmes intégrés et hétérogènes comportant des cavités à cristaux photoniques bidimensionnels au-dessus de guides d'ondes en silicium-sur-isolant. La réponse optomécanique de ces dispositifs est étudiée et atteste d'un couplage optomécanique impliquant à la fois les mécanismes dispersifs et dissipatifs. En contrôlant le couplage optique entre le guide d'onde intégré et le cristal photonique, nous avons pu varier et comprendre la contribution relative de ces couplages. Cette plateforme évolutive permet un contrôle sans précédent sur les mécanismes de couplage optomécanique, avec un avantage potentiel dans des expériences de refroidissement et pour le développement de circuits optomécaniques multi-éléments pour des applications tels que le traitement du signal par effets optomécaniques

Nonlinear imaging through a golden spiral multicore fiber

We report two-photon lensless imaging through a novel golden spiral multicore fiber. This unique layout optimizes the sidelobe levels, field of view, cross-talk, group delay and mode density to achieve a sidelobe contrast of atleast 10.9 dB. We demonstrate experimentally the ability to generate and scan a focal point with a femtosecond pulse and perform two-photon imaging.Comment: Submitted to Optics Letter

Extended field-of-view in a lensless endoscope using an aperiodic multicore fiber

We investigate lensless endoscopy using coherent beam combining and aperiodic multicore fibers (MCF). We show that diffracted orders, inherent to MCF with periodically arranged cores, dramatically reduce the field of view (FoV) and that randomness in MCF core positions can increase the FoV up to the diffraction limit set by a single fiber core, while maintaining MCF experimental feasibility. We demonstrate experimentally pixelation-free lensless endoscopy imaging over a 120 micron FoV with an aperiodic MCF designed with widely spaced cores. We show that this system is suitable to perform beam scanning imaging by simply applying a tilt to the proximal wavefront.Comment: Submitted to Optics Letter

Single-shot non-interferometric measurement of the phase transmission matrix in multicore fibers

A simple technique for far-field single-shot non-interferometric determination of the phase transmission matrix of a multicore fiber with over 100 cores is presented. This phase retrieval technique relies on the aperiodic arrangement of the cores.Comment: Submitted to Optics Letter

DINAMIKA GIBANJA PLINOVA OD MJESTA SPONTANOGA SAMOZAPALJENJA UGLJENA NA RADILIŠTIMA

The object of this paper is to study the specificity of the dynamics of carbon monoxide in mining to determine the location of the source of coal self-heating or spontaneous combustion. The Fire Dynamics Simulator software package was used to model the gas hazard of coal mine workings. Given the typical details for the western coal basin of Donbas geo metric dimensions of workings, properties of coal, etc., a model of a fragment of emergency mining of a coal mine was created, which allows for the display of geometric and physical similarity to processes in actual mine workings. The results of the simulation for the studied scenarios with different air supply systems related to the detection and location of sources of self-heating or spontaneous combustion in the coal mine workings were obtained and analysed. It was established that low-density fire gases are concentrated in the vault of the workings, where they slowly dissolve in the air, with the dissolution process being linear. It was revealed that air velocity up to 0.67 to 0.7 m/s contributes to the formation of fire gas flows, which move towards the ventilation flow, almost without mixing, which is referred to as bifurcation. Numerical parameters of fire gas dynamics in near-real conditions were established, which can become a basis for the detection and location of sources of endogenous thermodynamic processes in mine workings.U radu se analizira posebnost dinamike ugljikova monoksida u rudarstvu kako bi se odredio smještaj izvorišta samozagrijavanja i samozapaljenja ugljena. Uporabljen je programski paket Fire Dynamics Simulator, kojim je modeliran rizik od plina na radilištu rudnika. Ogledno istraživanje načinjeno je na zapadu ugljenih bazena Donbasa uzimajući u obzir geometrijske dimenzije radilišta, svojstva ugljena itd. Stvoren je model za izvanredno rudarenje ugljena u izvanrednim okolnostima koji se može primijeniti na stvarne uvjete (geometriju, fizička svojstva) ugljenokopa. Simulacija je izvedena s nekoliko scenarija opskrbe zrakom s obzirom na smještaj detektora i izvora samozagrijavanja ili samozapaljenja. Utvrđeno je kako su zapaljivi plinovi male gustoće nakupljeni uz svod radilišta, gdje se sporo miješaju sa zrakom tijekom procesa koji je linearan. Prikazano je kako brzina strujenja zraka od 0,67 do 0,7 m/s pridonosi stvaranju toka zapaljivih plinova koji se tada gibaju prema ventilacijskome sustavu gotovo bez miješanja, ali s pojavama bifurkacije. Brojčane vrijednosti dobivene simulacijom za dinamiku zapaljivih plinova odgovaraju gotovo potpuno stvarnim uvjetima, te model može biti temelj za opažanje i smještanje endogenih (unutarnjih) termodinamičkih procesa na rudarskim radilištima

Flexible lensless endoscope with a conformationally invariant multi-core fiber

The lensless endoscope represents the ultimate limit in miniaturization of imaging tools: an image can be transmitted through a (multi-mode or multi-core) fiber by numerical or physical inversion of the fiber's pre-measured transmission matrix. However, the transmission matrix changes completely with only minute conformational changes of the fiber, which has so far limited lensless endoscopes to fibers that must be kept static. In this letter we report for the first time a lensless endoscope which is exempt from the requirement of static fiber by designing and employing a custom-designed conformationally invariant fiber. We give experimental and theoretical validations and determine the parameter space over which the invariance is maintained

Optomécanique dans les résonateurs intégrés et hybrides à cristal photonique bi-dimensionel

Les systèmes optomécaniques, dans lesquels les vibrations d'un résonateur mécanique sont couplées à un rayonnement électromagnétique, ont permis l'examen de multiples nouveaux effets physiques. Afin d'exploiter pleinement ces phénomènes dans des circuits réalistes et d'obtenir différentes fonctionnalités sur une seule puce, l'intégration des résonateurs optomécaniques est obligatoire. Ici nous proposons une nouvelle approche pour la réalisation de systèmes intégrés et hétérogènes comportant des cavités à cristaux photoniques bidimensionnels au-dessus de guides d'ondes en silicium-sur-isolant. La réponse optomécanique de ces dispositifs est étudiée et atteste d'un couplage optomécanique impliquant à la fois les mécanismes dispersifs et dissipatifs. En contrôlant le couplage optique entre le guide d'onde intégré et le cristal photonique, nous avons pu varier et comprendre la contribution relative de ces couplages. Cette plateforme évolutive permet un contrôle sans précédent sur les mécanismes de couplage optomécanique, avec un avantage potentiel dans des expériences de refroidissement et pour le développement de circuits optomécaniques multi-éléments pour des applications tels que le traitement du signal par effets optomécaniques.Optomechanical systems, in which the vibrations of a mechanical resonator are coupled to an electromagnetic radiation, have permitted the investigation of a wealth of novel physical effects. To fully exploit these phenomena in realistic circuits and to achieve different functionalities on a single chip, the integration of optomechanical resonators is mandatory. Here, we propose a novel approach to heterogeneously integrated arrays of two-dimensional photonic crystal defect cavities on top of silicon-on-insulator waveguides. The optomechanical response of these devices is investigated and evidences an optomechanical coupling involving both dispersive and dissipative mechanisms. By controlling optical coupling between the waveguide and the photonic crystal, we were able to vary and understand the relative strength of these couplings. This scalable platform allows for unprecedented control on the optomechanical coupling mechanisms, with a potential benefit in cooling experiments, and for the development of multi-element optomechanical circuits in the frame of optomechanically-driven signal-processing applications

External Control of Dissipative Coupling in a Heterogeneously Integrated Photonic Crystal—SOI Waveguide Optomechanical System

Cavity optomechanical systems with an enhanced coupling between mechanical motion and electromagnetic radiation have permitted the investigation of many novel physical effects. The optomechanical coupling in the majority of these systems is of dispersive nature: the cavity resonance frequency is modulated by the vibrations of the mechanical oscillator. Dissipative optomechanical interaction, where the photon lifetime in the cavity is modulated by the mechanical motion, has recently attracted considerable interest and opens new avenues in optomechanical control and sensing. In this work we demonstrate an external optical control over the dissipative optomechanical coupling strength mediated by the modulation of the absorption of a quantum dot layer in a hybrid optomechanical system. Such control enhances the capability of tailoring the optomechanical coupling of our platform, which can be used in complement to the previously demonstrated control of the relative (dispersive to dissipative) coupling strength via the geometry of the integrated access waveguide