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Antiferromagnetic materials are promising platforms for next-generation spintronics owing to their fast dynamics and high robustness against parasitic magnetic fields. However, nanoscale imaging of the magnetic order in such materials with zero net magnetization remains a major experimental challenge. Here we show that non-collinear antiferromagnetic spin textures can be imaged by probing the magnetic noise they locally produce via thermal populations of magnons. To this end, we perform nanoscale, all-optical relaxometry with a scanning quantum sensor based on a single nitrogen-vacancy (NV) defect in diamond. Magnetic noise is detected through an increase of the spin relaxation rate of the NV defect, which results in an overall reduction of its photoluminescence signal under continuous laser illumination. As a proof-of-concept, the efficiency of the method is demonstrated by imaging various spin textures in synthetic antiferromagnets, including domain walls, spin spirals and antiferromagnetic skyrmions. This imaging procedure could be extended to a large class of intrinsic antiferromagnets and opens up new opportunities for studying the physics of localized spin wave modes for magnonics., 7 pages, 5 figures

Controlling the quantum properties of individual fluorescent defects in silicon is a key challenge towards advanced quantum photonic devices prone to scalability. Research efforts have so far focused on extrinsic defects based on impurities incorporated inside the silicon lattice. Here we demonstrate the detection of single intrinsic defects in silicon, which are linked to a tri-interstitial complex called W-center, with a zero-phonon line at 1.218${\mu}$m. Investigating their single-photon emission properties reveals new information about this common radiation damage center, such as its dipolar orientation and its photophysics. We also identify its microscopic structure and show that although this defect does not feature electronic states in the bandgap, Coulomb interactions lead to excitonic radiative recombination below the silicon bandgap. These results could set the stage for numerous quantum perspectives based on intrinsic luminescent defects in silicon, such as quantum integrated photonics, quantum communications and quantum sensing.

Nitrogen-Vacancy centers in diamond possess an electronic spin resonance that strongly depends on temperature, which makes them efficient temperature sensor with a sensitivity down to a few mK/$\sqrt{\rm Hz}$. However, the high thermal conductivity of the host diamond may strongly damp any temperature variations, leading to invasive measurements when probing local temperature distributions. In view of determining possible and optimal configurations for diamond-based wide-field thermal imaging, we here investigate, both experimentally and numerically, the effect of the presence of diamond on microscale temperature distributions. Three geometrical configurations are studied: a bulk diamond substrate, a thin diamond layer bonded on quartz and diamond nanoparticles dispersed on quartz. We show that the use of bulk diamond substrates for thermal imaging is highly invasive, in the sense that it prevents any substantial temperature increase. Conversely, thin diamond layers partly solve this issue and could provide a possible alternative for microscale thermal imaging. Dispersions of diamond nanoparticles throughout the sample appear as the most relevant approach as they do not affect the temperature distribution, although NV centers in nanodiamonds yield lower temperature sensitivities compared to bulk diamond., Comment: 5 pages, 3 figures

Control of the crystalline orientation of nitrogen-vacancy (NV) defects in diamond is here demonstrated by tuning the temperature of chemical vapor deposition (CVD) growth on a (113)-oriented diamond substrate. We show that preferential alignment of NV defects along the [111] axis is significantly improved when the CVD growth temperature is decreased. This effect is then combined with temperature-dependent incorporation of NV defects during the CVD growth to obtain preferential alignment over dense ensembles of NV defects spatially localized in thin diamond layers. These results demonstrate that growth temperature can be exploited as an additional degree of freedom to engineer optimized diamond samples for quantum sensing applications., 6 pages, 3 figures

International audience; Stochastic resonance is a general phenomenon usually observed in one-dimensional, amplitude modulated, bistable systems. We show experimentally the emergence of phase stochastic resonance in the bidimensional response of a forced nanoelectromechanical membrane by evidencing the enhancement of a weak phase modulated signal thanks to the addition of phase noise. Based on a general forced Duffing oscillator model, we demonstrate experimentally and theoretically that phase noise acts multiplicatively, inducing important physical consequences. These results may open interesting prospects for phase noise metrology or coherent signal transmission applications in nanomechanical oscillators. Moreover, our approach, due to its general character, may apply to various systems.

International audience; 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.

Light scattering by a two-dimensional photonic-crystal slab (PCS) can result in marked interference effects associated with Fano resonances. Such devices offer appealing alternatives to distributed Bragg reflectors and filters for various applications, such as optical wavelength and polarization filters, reflectors, semiconductor lasers, photodetectors, bio-sensors and non-linear optical components. Suspended PCS also have natural applications in the field of optomechanics, where the mechanical modes of a suspended slab interact via radiation pressure with the optical field of a high-finesse cavity. The reflectivity and transmission properties of a defect-free suspended PCS around normal incidence can be used to couple out-of-plane mechanical modes to an optical field by integrating it in a free-space cavity. Here we demonstrate the successful implementation of a PCS reflector on a high-tensile stress Si3N4 nanomembrane. We illustrate the physical process underlying the high reflectivity by measuring the photonic-crystal band diagram. Moreover, we introduce a clear theoretical description of the membrane scattering properties in the presence of optical losses. By embedding the PCS inside a high-finesse cavity, we fully characterize its optical properties. The spectrally, angular- and polarization-resolved measurements demonstrate the wide tunability of the membrane’s reflectivity, from nearly 0 to 99.9470±0.0025%, and show that material absorption is not the main source of optical loss. Moreover, the cavity storage time demonstrated in this work exceeds the mechanical period of low-order mechanical drum modes. This so-called resolved-sideband condition is a prerequisite to achieve quantum control of the mechanical resonator with light.

International audience; Light scattering by a two-dimensional photonic-crystal slab (PCS) can result in marked interference effects associated with Fano resonances. Such devices offer appealing alternatives to distributed Bragg reflectors and filters for various applications, such as optical wavelength and polarization filters, reflectors, semiconductor lasers, photodetectors, bio-sensors and non-linear optical components. Suspended PCS also have natural applications in the field of optomechanics, where the mechanical modes of a suspended slab interact via radiation pressure with the optical field of a high-finesse cavity. The reflectivity and transmission properties of a defect-free suspended PCS around normal incidence can be used to couple out-of-plane mechanical modes to an optical field by integrating it in a free-space cavity. Here we demonstrate the successful implementation of a PCS reflector on a high-tensile stress Si3N4 nanomembrane. We illustrate the physical process underlying the high reflectivity by measuring the photonic-crystal band diagram. Moreover, we introduce a clear theoretical description of the membrane scattering properties in the presence of optical losses. By embedding the PCS inside a high-finesse cavity, we fully characterize its optical properties. The spectrally, angular- and polarization-resolved measurements demonstrate the wide tunability of the membrane’s reflectivity, from nearly 0 to 99.9470±0.0025%, and show that material absorption is not the main source of optical loss. Moreover, the cavity storage time demonstrated in this work exceeds the mechanical period of low-order mechanical drum modes. This so-called resolved-sideband condition is a prerequisite to achieve quantum control of the mechanical resonator with light.

Les lasers sont multiples : en fonction de leurs caracteristiques physiques intrinseques (quel milieu a gain ? quelle cavite ? quel pompage ?), ils produisent des rayonnements couvrant des plages extremement vastes, tant du point de vue spectral – de l’extreme ultraviolet au lointain infrarouge – que temporel – du regime continu aux attosecondes – ou encore energetique – du nano au megajoule. C’est de cette impressionnante diversite que les lasers tirent leur capacite a repondre a tant d’applications differentes.Nous vous proposons dans cet article de faire un rapide tour d’horizon des differents types de lasers existants et de leurs performances.

Lorsque les dimensions des lasers deviennent submicroniques, la physique qui gouverne leur fonctionnement est modifiee : les effets quantiques sont alors preponderants et le role joue par l’emission spontanee devient tres important, non seulement au passage du seuil, mais aussi en regime d’emission stimulee. Les progres technologiques recents ont permis, ces dernieres annees, de fabriquer de telles sources de lumiere laser et de commencer a explorer cette nouvelle physique. Dans cet article, nous presentons l’architecture de ces nouveaux lasers et illustrons, par l’exemple du passage du seuil, la physique sous-jacente, qui reste encore incomprise.

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 integrate 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 the 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 an 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 framework of optomechanically-driven signal-processing applications.

The emission linewidth is a key figure of merit for a quantum emitter. This paper reports on the possibility of reducing the spectral linewidth of single-wall carbon nanotubes. It demonstrates an order of magnitude narrower linewidths compared to the available data due to the enhanced crystalline quality of the carbon nanotubes synthesized by using a laser ablation technique.

We present the optical optimization of an optomechanical device based on a suspended InP membrane patterned with a 2D near-wavelength grating (NWG) based on a 2D photonic-crystal geometry. We first identify by numerical simulation a set of geometrical parameters providing a reflectivity higher than 99.8 % over a 50-nm span. We then study the limitations induced by the finite value of the optical waist and lateral size of the NWG pattern using different numerical approaches. The NWG grating, pierced in a suspended InP 265 nm-thick membrane, is used to form a compact microcavity involving the suspended nano-membrane as end mirror. The resulting cavity has a waist size smaller than 10 $\mu$m and a finesse in the 200 range. It is used to probe the Brownian motion of the mechanical modes of the nanomembrane.

Lorsque les lasers deviennent de dimensions submicroniques, la physique qui les gouverne est significativement modifiee, car la mecanique quantique commence alors a affecter les mecanismes qui regissent l’emission de lumiere. Si ces lasers ont largement ete explores theoriquement par le passe, leur realisation recente a reouvert un grand nombre de questions, lancant ainsi un nouveau pan de recherche en physique des lasers.

Interferometric photon-correlation measurements, which correspond to the second-order intensity cross correlations between the two output ports of an unbalanced Michelson (or Mach-Zehnder) interferometer, are sensitive to both amplitude and phase fluctuations of an incoming beam of light. Here, we present the theoretical framework behind these measurements and show that they can be used to unambiguously differentiate a coherent wave undergoing dynamical amplitude and phase fluctuations from a chaotic state of light. This technique may thus be used to characterize the output of nanolasers and monitor the onset of coherent emission.

We present a novel experimental technique that can differentiate unequivocally between chaotic light and coherent light with amplitude fluctuations, and thus permits to characterize unambiguously the output of a laser. This technique consists of measuring the second-order intensity cross-correlation at the outputs of an unbalanced Michelson interferometer. It is applied to a chaotic light source and to the output of a semiconductor nanolaser whose "standard" intensity correlation function above-threshold displays values compatible with a mixture of coherent and chaotic light. Our experimental results demonstrate that the output of such lasers is not partially chaotic but is indeed a coherent state with amplitude fluctuations., Comment: 5 pages, 3 figures

International audience; A plasmonic microcavity providing broadband control of spontaneous emission for large and sparse semiconductor quantum dots emitting at telecommunications wavelengths is proposed. By designing and fabricating such a cavity, we demonstrate a broadband Purcell effect with spontaneous emission enhancement over a broad spectral range of Dk ’ 20nm with a 3.9-fold maximum enhancement, as well as inhibition over Dk ’ 100 nm around 1.3 lm. The broadband feature relaxes the constraint on spectral matching between the dot emission and the cavity mode, favourable for implementing efficient non-classical light sources or nanoscale lasers.

We investigate the non-linear mechanical dynamics of a nano-optomechanical mirror formed by a suspended membrane pierced by a photonic crystal. By applying to the mirror a periodic electrostatic force induced by interdigitated electrodes integrated below the membrane, we evidence superharmonic resonances of our nano-electro-mechanical system; the constant phase shift of the oscillator across the resonance tongues is observed on the onset of principal harmonic and subharmonic excitation regimes.

The topography and the electronic structure of $\mathrm{InAsP}/\mathrm{InP}$ quantum dots are probed by cross-sectional scanning tunneling microscopy and spectroscopy. The study of the local density of states in such large quantum dots confirms the discrete nature of the electronic levels whose wave functions are measured by differential conductivity mapping. Because of their large dimensions, the energy separation between the discrete electronic levels is low, allowing for quantization in both the lateral and growth directions as well as the observation of the harmonicity of the dot lateral potential.

Non-linear dynamical systems involving small populations of individuals may sustain oscillations in the population densities arising from the discrete changes in population numbers due to random events. By applying these ideas to nanolasers operating with small numbers of emitting dipoles and photons at threshold, we show that such lasers should display photon and dipole population cycles above threshold, which should be observable as a periodic modulation in the second-order correlation function of the nanolaser output. Such a modulation was recently reported in a single-mode vertical-cavity surface-emitting semiconductor laser., Comment: 7 pages, 5 figures

Quantum radiation pressure noise has never been experimentally demonstrated, though it has been predicted for more than thirty years. It is, however, expected to limit the low-frequency sensitivity of second generation gravitational-wave interferometers. We have demonstrated classical radiation-pressure-induced correlations between two optical beams sent into the same high-finesse cavity with a moving mirror. Our two-beam scheme can be used to retrieve quantum noise embedded in an overwhelming classical noise, and has applications both in high-sensitivity measurements and in quantum optics.

The optical properties of single InAs${}_{1\ensuremath{-}x}$P${}_{x}/$InP quantum dots are investigated by spectrally resolved and time-resolved photoluminescence measurements as a function of excitation power. In the short-wavelength region (below 1.45 $\ensuremath{\mu}$m), the spectra display sharp distinct peaks resulting from the discrete electron-hole states in the dots, while in the long-wavelength range (above 1.45 $\ensuremath{\mu}$m), these sharp peaks lie on a broad spectral background. In both regions, cascade emission observed by time-resolved photoluminescence confirms that the quantum dots possess discrete exciton and multiexciton states. Single photon emission is reported for the dots emitting at 1.3 $\ensuremath{\mu}$m through antibunching measurements.

Nanoscale lasers sustain a few optical modes so that the fraction of spontaneous emission $\ensuremath{\beta}$ funnelled into the useful (lasing) mode is high (of the order of 10${}^{\ensuremath{-}1}$) and the threshold, which traditionally corresponds to an abrupt kink in the light-in--light-out curve, becomes ill defined. We propose an alternative definition of the threshold that is based on the dynamical response of the laser and is valid even for $\ensuremath{\beta}=1$ lasers. The laser dynamics is analyzed through a reconstruction of its phase-space trajectory for pulsed excitations. Crossing the threshold, brings about a change in the shape of the trajectory and in the area contained in it. An unambiguous determination of the threshold in terms of this change is shown theoretically and illustrated experimentally in a photonic-crystal laser.

International audience; We have designed photonic crystal suspended membranes with optimized optical and mechanical properties for cavity optomechanics. Such resonators sustain vibration modes in the megahertz range with quality factors of a few thousand. Thanks to a two-dimensional square lattice of holes, their reflectivity at normal incidence at 1064 nm reaches values as high as 95%. These two features, combined with the very low mass of the membrane, open the way to the use of such periodic structures as deformable end-mirrors in Fabry-Perot cavities for the investigation of cavity optomechanical effects

We experimentally investigate the optomechanical properties of a conventional two-dimensional suspended photonic crystal defect cavity. Particularly, we measure localized mechanical modes in the GHz regime exhibiting high values of the optomechanical vacuum coupling rate exceeding 250 kHz.

International audience; We report on the higher-order photon correlations of a high-$\beta$ nanolaser under pulsed excitation at room temperature. Using a multiplexed four-element superconducting single photon detector we measured g$^{(n)}(\vec{0})$ with $n$=2,3,4. All orders of correlation display partially chaotic statistics, even at four times the threshold excitation power. We show that this departure from coherence and Poisson statistics is due to the quantum fluctuations associated with the small number of dipoles and photons involved in the lasing process.

A novel metal-coated nanocylinder-cavity architecture fully compatible with III-V GaInAs technology and benefiting from a broad spectral range enhancement of the local density of states is proposed as an integrated source of nonclassical light. Because of a judicious selection of the mode volume, the cavity combines good collection efficiency ($\ensuremath{\approx}45%$), large Purcell factors ($\ensuremath{\approx}15$) over a 80 nm spectral range, and a low sensitivity to inevitable spatial mismatches between the single emitter and the cavity mode. This represents a decisive step towards the implementation of reliable solid-state devices for the generation of entangled photon pairs at infrared wavelengths.

We report on lasing at room temperature and at telecommunications wavelength from photonic crystal nanocavities based on InAsP/InP quantum dots. Such laser cavities with a small modal volume and high quality factor display a high spontaneous emission coupling factor (beta). Lasing is confirmed by measuring the second-order autocorrelation function. A smooth transition from chaotic to coherent emission is observed, and coherent emission is obtained at eight times the threshold power.

International audience; We report on the control of the spontaneous emission dynamics from InAsP self-assembled quantum dots emitting in the telecommunications C-band and weakly coupled to the mode of a double heterostructure cavity etched on a suspended InP membrane at room temperature. The quality factor of the cavity mode is 44x10^3 with an ultra-low modal volume of the order of 1.2 lambda/n)^3, inducing an enhancement of the spontaneous emission rate of up a factor of 2.8 at 300 K.

International audience; The dynamic response of InAsP quantum dots grown on InP(001) substrates by low-pressure Metalorganic Vapor Phase Epitaxy emitting around 1.55 $\mu$m, is investigated by means of time-resolved microphotoluminescence as a function of temperature. Exciton lifetime steadily increases from 1 ns at low temperature to reach 4 ns at 300K while the integrated photoluminescence intensity decreases only by a factor of 2/3. These characteristics give evidence that such InAsP/InP quantum dots provide a strong carrier confinement even at room temperature and that their dynamic response is not affected by thermally activated non-radiative recombination up to room temperature.

International audience; We report on a series of experiments on the dynamics of spontaneous emission controlled nanolasers. The laser cavity is a photonic crystal slab cavity, embedding self-assembled quantum dots as gain material. The implementation of cavity electrodynamics effects increases significantly the large signal modulation bandwidth, with measured modulation speeds of the order of 10 GHz while keeping an extinction ratio of 19 dB. A linear transient wavelength shift is reported, corresponding to a chirp of less than 100 pm for a 35-ps laser pulse. We observe that the chirp characteristics are independent of the repetition rate of the laser up to 10 GHz.

We report on a scheme for the creation of time-bin entangled states out of two subsequent single photons. Both photons arrive on the same input port of a beamsplitter and the situation in which the photons leave the beamsplitter on different output ports is post-selected. We derive a full quantum mechanical analysis of such time-bin entanglement for emitters subject to uncorrelated dephasing processes and apply this model to sequential single photons emerging from a single semiconductor quantum dot. Our results indicate that the visibility of entanglement is degraded by decoherence effects in the quantum dot, but can be restored by use of CQED effects, namely the Purcell effect., Comment: Accepted EPJD

We study the nonlinear dynamics induced in suspended nanomembranes by their clampings. The nonlocal character of the nonlinearity is demonstrated via intermode couplings. We also monitor the resonator phase-space trajectory and characterize its mechanical response in the presence of a strong pump excitation. We observe a shift in the oscillation frequency and phase conjugation of the mechanical mode. Such nonlinear effects are inherent to any submicron-scale mechanical resonator and are expected to play a role in their quantum dynamics as well.

International audience; Using a fully vectorial frequency-domain aperiodic Fourier modal method, we study nanowire metallic mirrors and their photonic performance. We show that the performance of standard quarter-wave Bragg mirrors at subwavelength diameters is surprisingly poor, while engineered metallic mirrors that incorporate a thin dielectric adlayer may offer reflectance larger than 90% even for diameters as small as lambda/5.

International audience; Pillar microcavities are subject to two common fabrication artifacts: Bragg mirror corrugation and oxide deposit cladding. In this letter the authors investigate the impact of these features on the quality factor. A quasiperiodic variation of the quality factor as a function of the pillar diameter is experimentally observed and well described by theory. Moreover, observation of quality factors in excess of 1500, close to the theoretical limit, is reported for 600-nm-diameter GaAs micropillars bounded by AlGaAs/GaAs Bragg mirrors.

Periodically structured materials can sustain both optical and mechanical modes. Here we investigate and observe experimentally the optomechanical properties of a conventional two-dimensional suspended photonic crystal defect cavity with a mode volume of $\sim$$3(\lambda/n)^{3}$. Two families of mechanical modes are observed: flexural modes, associated to the motion of the whole suspended membrane, and localized modes with frequencies in the GHz regime corresponding to localized phonons in the optical defect cavity of diffraction-limited size. We demonstrate direct measurements of the optomechanical vacuum coupling rate using a frequency calibration technique. The highest measured values exceed 250 kHz, demonstrating strong coupling of optical and mechanical modes in such structures., Comment: 11 Pages, 8 Figures

Nonlinearities in nanomechanical systems can arise from various sources such as spring and damping mechanisms and resistive, inductive, and capacitive circuit elements. Beyond fundamental interests for testing the dynamical response of discrete nonlinear systems with many degrees of freedom, non-linearities in nanomechanical devices, open new routes for nanomechanical sensing, and signal processing.The nonlinear response of a nanomechanical resonator consisting in a suspended photonic crystal membrane acting as a deformable mirror has been investigated. The low-mass and high reflectivity of suspended membranes pierced by a two-dimensional photonic crystal, makes them good candidates as electro-optomechanical resonator. Actuation of the membrane motion in the MHz frequency range is achieved via interdigitated electrodes placed underneath the membrane. The choice of these electrodes is due to the fact they are able to uniformly actuate these membranes. The processing of such platforms relies on 3D-heterogenous integration process.The applied electrostatic force induces mechanical non-linearities, in particular bistability, superharmonic resonances and stochastic resonance.The membrane is actuated by an electric load V(t) = Vdc + Vac cos(w.t), where Vdc is the DC polarization voltage, Vac the amplitude of the applied AC voltage, and w; the excitation frequency. The system acts as a capacitive system and thus the force applied on the membrane varies as a quadratic function of the applied voltage. Application of either DC or AC voltages can have different implications. Increasing the DC voltage increases the polarizing voltage on the material which in turn causes modulation of the eigenfrequency of the membranes. While an increase in the periodic AC voltage causes the membrane to oscillate more, pushing the system towards non-linear regime.In a first series of experiments, the membrane is actuated resonantly, with an excitation frequency w; equal to the fundamental mechanical modes frequency wm. From the frequency response spectra of the system it was possible to identify different mechanical modes of these membranes via optical measurements. For increased actuation voltages, bistability effects are observed with two different behaviors (spring hardening or softening). The mechanical nonlinearities due to stretching at the clamping point dominate the resonator dynamics.The most commonly used method to act upon the membrane is the primary-resonance excitation, in which the frequency of the excitation is tuned closed to the fundamental natural frequency of the nanostructure. Superharmonic resonance can also be implemented. It consists in applying an excitation frequency w; equal to wm/n, with n being integer. Existence of these superharmonic resonances is highly dependent on the non-linearity of the system. For example existence of n-th order non-linearity results in presence wm/n superharmonic resonance. In a second series of experiments, frequency-power sweep for superharmonic resonance has been performed, by modulating the electric load at a frequency wm/n and recording the response of the membrane at the fundamental frequency wm. High-order superharmonic resonances are observed with n=2 up to 8. Under superharmonic excitation, the control of the phase across the resonance has been shown for every observed resonance.In the next set of experiments, we used the nonlinearity existing in the system to perform stochastic resonance. The idea of stochastic resonance is amplification of a weak signal (with low frequency) by means of noise injected (higher frequency) in a nonlinear system. For our system we were able to achieve stochastic resonance with both amplitude and phase noise. A comparative study between these two schemes was also done in details. The idea of observing stochastic resonance in phase is very interesting as it opens doors to realize phase encoded communications., Les nonlinéarités dans les systèmes nanomécaniques peuvent provenir d’effets dispersif ou dissipatif et ce dans divers systèmes (résistifs, inductifs et capacitifs). Au-delà de l’intérêt fondamental pour tester la réponse dynamique d’un système non-linéaire à plusieurs dégrées de libertés, les nonlinéarités de tels systèmes ouvre la voie vers des capteurs nanomécanique et le traitement du signal. Le résonateur nanomécanique dont la réponse nonlinéaire est étudié, est une membrane suspendue à cristal photonique bidimensionnel utilisée comme miroir déformable. Sa faible masse et sa haute réflectivité en font un candidat idéal pour l’électro-opto-mécanique. L’actuation d’une telle membrane dans le domaine fréquentiel du MHz est rendu possible par des électrodes inter-digitées en dessous de la membrane assurant ainsi l’uniformité de la force d’actuation sur cette dernière. La fabrication de telles structures est basée sur l’intégration hétérogène 3D.La force électrostatique qui s’applique sur la membrane induit des non-linéarités mécaniques avec notamment un effet bistable, des résonances superharmoniques et des résonances stochastiques.La membrane est mise en mouvement par un potentiel électrique V(t) = Vdc + Vac cos(w.t), où Vdc est l’amplitude du courant continu, Vac l’amplitude du courant alternatif à la fréquence d’excitation w;. Le système se comporte alors comme une capacité de sorte que la force qui s’applique sur la membrane varie de manière quadratique avec la tension appliquée. Selon la tension DC ou AC, le comportement de la structure est différent. L’augmentation de la tension DC induit une augmentation de la tension de polarisation sur le matériau qui par conséquent modifie la fréquence propre de la membrane. Tandis que l’augmentation de la tension AC cause l’augmentation de l’amplitude des oscillations de la membrane pouvant aller jusqu’à atteindre le régime non-linéaire.Dans une première série de mesure, la membrane est excitée à la résonance avec une fréquence w; égale à la fréquence du mode mécanique fondamental wm. A partir de la réponse fréquentielle du système, il est possible d’identifier différents modes mécaniques de la membrane sondé optiquement. Pour une excitation plus importante, il est possible d’observer des effets de bistabilité mécanique. Ces non-linéarités sont dues à l’élongation au niveau des points d’ancrage de la membrane.La méthode la plus commune pour agir sur la membrane est l’excitation proche de la résonance fondamentale. Cependant la technique de la résonance superharmonique peut également être utilisée. Cela consiste à appliquer la fréquence d’excitation w; à une fréquence égale à wm/n où n est un entier. La possibilité d’utiliser cette technique est fortement dépendante des nonlinéarités présentes dans le système. Ainsi, l’existence d’une résonance super harmonique à wm/n résulte de la présence d’une nonlinéarité d’ordre n. Dans une seconde série de mesure, un balayage des résonances superharmoniques en fonction de la fréquence et de la puissance a été réalisé en modulant la tension à la fréquence wm/n et en enregistrant la réponse de la membrane autour de wm. Il a été ainsi possible d’observer des résonances superharmoniques allant de n=2 jusqu’à 8. Il a également été possible d’obtenir l’évolution de la phase le long des résonances et ce pour toutes celles observées.Dans une dernière série de mesure, nous utilisons la nonlinéarité présente pour observer des effets de résonance stochastique. L’idée est d’amplifier un signal de faible amplitude (basse fréquence) en injectant du bruit (haute fréquence) dans le système nonlinéaire. Dans le cas de notre système, nous avons été capables d’observer des résonances stochastiques à la fois en amplitude et en phase. Une étude comparative de ces deux régimes est détaillée. Le fait de pouvoir observer la résonance stochastique en phase peut permettre d’envisager la réalisation de communications codées en phase.

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.