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International audience; In this work we investigate the properties of negatively charged nitrogen-vacancy (NV À) centres created during single crystal diamond growth by chemical vapour deposition (CVD) on [113]-oriented substrates and with N 2 O as a dopant gas. The use of spin echo and double electron-electron resonance (DEER) allows us to assess NV À ratio with respect to substitutional nitrogen impurities (N 0 s) incorporated during growth, a critical figure of merit for quantum technologies. We demonstrate that, at moderate growth temperatures (800 C), dense NV À ensembles of several hundreds of ppb (800 ppb for 50 ppm of added N 2 O) and with exceptionally high NV À / N 0 s ratios of up to 25% can be achieved. This NV À creation yield is higher by at least an order of magnitude to that typically obtained on standard [100]-grown diamonds and comparable to the best values reported for electron-irradiated diamonds. The material obtained here thus advantageously combines a high NV À density, high creation yield, long coherence times of several tens of ms together with a partial preferential orientation. These are highly desirable requirements for diamond-based quantum sensors that may spur new developments with this crystalline orientation leading to improved performance and sensitivity.

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.

In a large number of experiments or devices, noise is usually viewed as an undesirable disturbance, hindering the measurement sensitivity or device performances. In some circumstances however, noise-induced phenomena can help, as in the case of stochastic resonance whereby a small coherent signal gets amplified resonantly by application of external noise. Stochastic resonance occurs in a wide class of nonlinear systems, in neurobiology [1], mesoscopic physics [2], photonics [3], atomic physics [4], mechanics [5, 6]… Stochastic resonance is a kind of synchronization of the switching events. If a weak periodic forcing is applied to the oscillator, the initially symmetrical double-well potential gets tilted asymmetrically up and down, periodically raising and lowering the potential barrier. Although the periodic forcing is too weak to let the membrane switch periodically from one potential well into the other one, noise-induced hopping between the potential wells can become synchronized with the weak period forcing. This time coincidence takes place when the average waiting time between noise-induced interwell transitions is comparable with half the period of the periodic forcing. Thus stochastic resonance corresponds to the noise-assisted amplification of a weak coherent input that is too feeble to induce hopping between the two stable states.

Two-dimensional photonic crystal slabs (PCS) offer an appealing alternative to distributed Bragg reflectors or filters for various applications. Indeed, their scattering properties, governed by Fano-resonances, have been used in areas as diverse as optical wavelength and polarization filters, reflectors, semiconductor lasers, photodetectors, bio-sensors, or non-linear optical components. Suspended PCSs also find 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. We have demonstrated the successful implementation of a PCS reflector on a high-tensile stress Si3N4 nanomembrane. We could measure the photonic crystal band diagram with a spectrally, angular, and polarization resolved setup. Moreover, a cavity with a finesse as high as 12 000 was formed using the suspended membrane as end-mirror of a Fabry-Perot cavity. These achievements allow us to operate in the resolved sideband regime where the optical storage time exceeds the mechanical period of low-order mechanical drum modes. This condition is a prerequisite to achieve quantum control of the mechanical resonator with light.

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.

Single photon emission is investigated for fast radiative quantum dots. A simple model including capture process shows that the probability that a second photon is emitted increases when decreasing the exciton radiative lifetime. This effect is experimentally demonstrated through photon correlation measurements on single GaAs quantum dots presenting various radiative lifetime. The same model is used to estimate the second order autocorrelation function for an InAs quantum dot experiencing strong Purcell effect. The calculation shows the limitations of using Purcell effect to realize efficient single photon sources. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

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.

We report on optomechanical effects in 2D photonic crystal defect cavities coupled to integrated silicon waveguides of different widths. Mechanical modes are observed systematically on a chip scale. By tuning the excitation laser wavelength, we observe optical spring effects. We extract optomechanical coupling coefficients and demonstrate the dispersive and dissipative nature of optomechanical coupling. Their relative contribution can be controlled by modifying the access waveguide width, thereby paving the way for a control of optomechanical coupling on the wafer level.

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.

Quantum propagation of indistinguishable photons in coupled waveguide lattices is analyzed in the asymptotic limit. Such an approach reveals the existence of two main relevant families of modes supported by the photonic lattice: localized side modes and Floquet-Bloch eigenmodes delocalized over the array. Under two-photon injection, the modal framework unravels the photon bunching and antibunching effects occurring in coupled waveguide lattices. In particular, photon correlations in the Floquet-Bloch modes are exhibited. Engineering of the propagation in such delocalized eigenmodes through patterning of the array coupling constant may open the way to discrete photonics platforms implementing efficient modal manipulation of quantum light involving large photon-number states.

To demonstrate strong coupling regime for a single quantum dot inside an optical microcavity, large oscillator strength quantum dots are needed. We show that quantum dots formed by the interface fluctuations of a thin GaAs quantum well are ideal systems for this purpose since they can present an oscillator strength larger than 100. By inserting a GaAs QD inside a state of the art microdisk microcavity, we demonstrate the strong coupling regime with a Rabi splitting of 400 μeV.

Les boites quantiques semi-conductrices sont des candidats prometteurs pour la generation d'etats quantiques de la lumiere, tels que des photons uniques. En isolant ces nano-emetteurs dans des microcavites optiques, ces emetteurs uniques peuvent produire des photons identiques: l'exaltation du taux d'emission spontanee permet de contourner les effets de perte de coherence de l'emetteur, qui marquent aleatoirement les photons emis. L'indiscemabilite entre photons est sondee via des experiences d'interference a deux photons. La visibilite du processus d'interference indique des taux d'indiscernabilite superieurs a 70% entre photons emis par une boite isolee en cavite micropilier ou a cristal photonique.

The correlation between the photons emitted by an optically pumped single quantum dot is investigated. The correlation function on a single dot isolated in a mesa shows that only one photon is emitted at a time at the exciton frequency. These quantum states of light can be generated with a high quantum efficiency, with the use of cavity effects: surrounding the dot by a pillar microcavity not only increases significantly the single photon flux but also allows the preparation of single photons all in the same quantum state (same spatial mode and same polarization). © 2002 Published by Elsevier Science B.V.

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.

We present atomic-scale characterization of site-controlled InAs/InP(001) quantum dots grown by metal-organic chemical vapor deposition using nano-area selective area growth. We have developed for this purpose a process combining e-beam lithography, inductively coupled-plasma etching and focused ion beam etching to isolate a few quantum dots. The size, the shape and the composition of the quantum dots are investigated by Scanning Transmission Electron Microscopy. A comparison with the well-known single self-assembled quantum dots highlights the specificities of our growth mode compared to the Stranski–Krastanov growth mode.

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.

We demonstrate the feasibility of a new approach based on the nano selective area growth (nano-SAG), which allows the precise spacial localization, in the nanometer scale, of InAs/InP quantum dots (QDs) grown by low-pressure metal organic vapor-phase epitaxy. By using the hydrogen silsesquioxane-negative resist, we partially pattern the substrate in only one step (e-beam lithography) with dielectric masks containing nano-openings. We demonstrate that the one-step nano-SAG technique leads to the formation of site-controlled InAs/InP QDs with good structural properties, and allows the good control of the growth rate and thus of the QD size into the nano-openings.

We have designed, fabricated and characterized a nanomembrane which could be used as a moving end mirror of a Fabry-Perot cavity. The high reflectivity and optimized mechanical properties of the membrane should allow us to demonstrate the mechanical ground state of the membrane. As any sub-micron mechanical resonator, our system demonstrates nonlinear dynamical effects. We characterize the mechanical response to a strong pump drive and observe a shift in the oscillation frequency and phase conjugation of the mechanical mode. Such nonlinear effects are expected to play a role in the quantum dynamics of the membrane as well.

The authors have developed small radius of curvature coupling mirrors integrated in a 100 μm length cavity. The detection sensitivity of this system is at the 10-16 m/(Hz)1/2 level allowing us to observe its thermal noise. This sensitivity is also theoretically sufficient to observe ground state quantum fluctuations of the photonic crystal nanomembrane. As any active cooling relies on adding a viscous damping force and has the reduction of the Q-factor of the resonator as a consequence. It is then crucial to design a device with a very high mechanical quality. Different geometries, materials, and stresses for the membrane have been tested. The authors have achieved to realize structures with a Q-factor of 20 000 at room temperature and 65 000 at 20 K.

We quantitatively explore the ability of coupled waveguide arrays to characterize and manipulate two-photon and NOON states. We emphasize in particular the potential of patterned arrays in which the coupling is structured.

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 demonstrate that a single photoexcited InGaAs semiconductor quantum dot (QD) grown by organo-metallic chemical vapor deposition on prepatterned substrates emits one photon at a time, with no uncontrolled background photon emission, making it an excellent single photon emitter. Moreover, our fabrication technique offers complete site control and small inhomogeneous broadening of QD arrays, which is essential for the practical implementation of QDs in efficient solid-state single photon emitting devices.

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

The development of single photon sources is of great interest for both fundamental studies and further development of long-distance quantum cryptography. Semiconductor Quantum Dots (QDs) based on III–V materials are of special interest for this purpose since they can be inserted into microcavities to benefit from Purcell effect. The Stranski-Krastanow (SK) growth mode is the widely used method to synthesize self-assembled QDs. However, the random distribution of the SK QDs does not allow a deterministic localization of the QDs, required for the spatial localization of a single QD on the electromagnetic-field maximum of a cavity.

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.