Whispering-Gallery Quantum-Well Exciton Polaritons in an Indium Gallium Arsenide Microdisk Cavity.

Despite appealing high-symmetry properties that enable strong spatial confinement and ultrahigh-Q, optical whispering-gallery modes of spherical and circular resonators have been absent from the field of quantum-well exciton polaritons. Here we observe whispering-gallery exciton polaritons in a gallium arsenide microdisk cavity filled with indium gallium arsenide quantum wells, the test bed materials of polaritonics. Strong coupling is evidenced in photoluminescence and resonant spectroscopy accessed through concomitant confocal microscopy and near-field optical techniques. Excitonic and optical resonances are tuned by varying temperature and disk radius, revealing Rabi splittings between 5 and 10 meV. A dedicated analytical quantum model for such circular whispering-gallery polaritons is developed, which reproduces the measured values. At high power, lasing is observed and accompanied by a blueshift of the emission consistent with the regime of polariton lasing. With experimental methods and theory now established, whispering-gallery-mode polaritons in round dielectric resonators appear as a new viable platform toward low loss polaritonics.

Simultaneous Optical and Mechanical Sensing Based on Optomechanical Resonators.

Optical and mechanical resonators have each been abundantly employed in sensing applications, albeit following separate development. Here we show that bringing together optical and mechanical resonances in a unique sensing device significantly improves the sensor performance. To that purpose, we employ nanoscale optomechanical disk resonators that simultaneously support high quality optical and mechanical modes localized in tiny volumes, which provide extraordinary sensitivities. We perform environmental sensing, but the conclusions of our work extend to other sensing applications. First, we determine optical and mechanical responsivities to temperature and relative humidity changes. Second, by characterizing mechanical and optical frequency stabilities, we determine the corresponding limits of detection. Mechanical modes appear more sensitive to relative humidity changes, while optical modes appear more sensitive to temperature ones, reaching, respectively, 0.05% and 0.6 mK of independent resolution. We then prove that simultaneous optical and mechanical monitoring enables disentangling both effects and demonstrates 0.1% and 1 mK resolution, even considering that both parameters may change at the same time. Finally, we highlight the importance of actively tracking the optical mode when optomechanical sensor devices. Not doing so enforces tedious independent calibration, influences the device sensitivity during the experiment, and shortens the sensing range. The present work hence clarifies the requirements for the optimal operation of optomechanical sensors, which will be of importance for chemical and biological sensing.

Optomechanical measurement of single nanodroplet evaporation with millisecond time-resolution.

Tracking the evolution of an individual nanodroplet of liquid in real-time remains an outstanding challenge. Here a miniature optomechanical resonator detects a single nanodroplet landing on a surface and measures its subsequent evaporation down to a volume of twenty attoliters. The ultra-high mechanical frequency and sensitivity of the device enable a time resolution below the millisecond, sufficient to resolve the fast evaporation dynamics under ambient conditions. Using the device dual optical and mechanical capability, we determine the evaporation in the first ten milliseconds to occur at constant contact radius with a dynamics ruled by the mere Kelvin effect, producing evaporation despite a saturated surrounding gas. Over the following hundred of milliseconds, the droplet further shrinks while being accompanied by the spreading of an underlying puddle. In the final steady-state after evaporation, an extended thin liquid film is stabilized on the surface. Our optomechanical technique opens the unique possibility of monitoring all these stages in real-time.

Real-Time Sensing with Multiplexed Optomechanical Resonators.

Nanoelectromechanical resonators have been successfully used for a variety of sensing applications. Their extreme resolution comes from their small size, which strongly limits their capture area. This leads to a long analysis time and the requirement for large sample quantity. Moreover, the efficiency of the electrical transductions commonly used for silicon resonators degrades with increasing frequency, limiting the achievable mechanical bandwidth and throughput. Multiplexing a large number of high-frequency resonators appears to be a solution, but this is complex with electrical transductions. We propose here a route to solve these issues, with a multiplexing scheme for very high-frequency optomechanical resonators. We demonstrate the simultaneous frequency measurement of three silicon microdisks fabricated with a 200 mm wafer large-scale process. The readout architecture is simple and does not degrade the sensing resolutions. This paves the way toward the realization of sensors for multiparametric analysis with an extremely low limit of detection and response time.

Multimode Optomechanical Weighting of a Single Nanoparticle.

We demonstrate multimode optomechanical sensing of individual nanoparticles with a radius between 75 and 150 nm. A semiconductor optomechanical disk resonator is optically driven and detected under ambient conditions, as nebulized nanoparticles land on it. Multiple mechanical and optical resonant signals of the disk are tracked simultaneously, providing access to several pieces of physical information about the landing analyte in real time. Thanks to a fast camera registering the time and position of landing, these signals can be employed to weight each nanoparticle with precision. Sources of error and deviation are discussed and modeled, indicating a path to evaluate the elasticity of the nanoparticles on top of their mere mass. The device is optimized for the future investigation of biological particles in the high megadalton range, such as large viruses.

Non-Hermitian bath model for arrays of coupled nanoresonators.

Nanophotonics systems have recently been studied under the perspective of non-Hermitian physics. Given their potential for wavefront control, nonlinear optics and quantum optics, it is crucial to develop predictive tools to assist their design. We present here a simple model relying on the coupling to an effective bath consisting of a continuum of modes to describe systems of coupled resonators, and test it on dielectric nanocylinder chains accessible to experiments. The effective coupling constants, which depend non-trivially on the distance between resonators, are extracted from numerical simulations in the case of just two coupled elements. The model predicts successfully the dispersive and reactive nature of modes for configurations with multiple resonators, as validated by numerical solutions. It can be applied to larger systems, which are hardly solvable with finite-element approaches.

Electro-Optomechanical Modulation Instability in a Semiconductor Resonator.

In semiconductor nano-optomechanical resonators, several forms of light-matter interaction can enrich the canonical radiation pressure coupling of light and mechanical motion and give rise to new dynamical regimes. Here, we observe an electro-optomechanical modulation instability in a gallium arsenide disk resonator. The regime is evidenced by the concomitant formation of regular and dense combs in the radio-frequency and optical spectrums of the resonator associated with a permanent pulsatory dynamics of the mechanical motion and optical intensity. The mutual coupling between light, mechanical oscillations, carriers, and heat, notably through photothermal interactions, stabilizes an extended mechanical comb in the ultrahigh frequency range that can be controlled optically.

Optomechanical mass spectrometry.

Nanomechanical mass spectrometry has proven to be well suited for the analysis of high mass species such as viruses. Still, the use of one-dimensional devices such as vibrating beams forces a trade-off between analysis time and mass resolution. Complex readout schemes are also required to simultaneously monitor multiple resonance modes, which degrades resolution. These issues restrict nanomechanical MS to specific species. We demonstrate here single-particle mass spectrometry with nano-optomechanical resonators fabricated with a Very Large Scale Integration process. The unique motion sensitivity of optomechanics allows designs that are impervious to particle position, stiffness or shape, opening the way to the analysis of large aspect ratio biological objects of great significance such as viruses with a tail or fibrils. Compared to top-down beam resonators with electrical read-out and state-of-the-art mass resolution, we show a three-fold improvement in capture area with no resolution degradation, despite the use of a single resonance mode.

Publisher Correction: Optomechanical detection of vibration modes of a single bacterium.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Optomechanical detection of vibration modes of a single bacterium.

Low-frequency vibration modes of biological particles, such as proteins, viruses and bacteria, involve coherent collective vibrations at frequencies in the terahertz and gigahertz domains. These vibration modes carry information on their structure and mechanical properties, which are good indicators of their biological state. In this work, we harnessed a particular regime in the physics of coupled mechanical resonators to directly measure these low-frequency mechanical resonances of a single bacterium. We deposit the bacterium on the surface of an ultrahigh frequency optomechanical disk resonator in ambient conditions. The vibration modes of the disk and bacterium hybridize when their associated frequencies are similar. We developed a general theoretical framework to describe this coupling, which allows us to retrieve the eigenfrequencies and mechanical loss of the bacterium low-frequency vibration modes (quality factor). Additionally, we analysed the effect of hydration on these vibrational modes. This work demonstrates that ultrahigh frequency optomechanical resonators can be used for vibrational spectrometry with the unique capability to obtain information on single biological entities.

Permanent Directional Heat Currents in Lattices of Optomechanical Resonators.

We study the phonon dynamics in lattices of optomechanical resonators where the mutually coupled photonic modes are coherently driven and the mechanical resonators are uncoupled and connected to independent thermal baths. We present a general procedure to obtain the effective Lindblad dynamics of the phononic modes for an arbitrary lattice geometry, where the light modes play the role of an effective reservoir that mediates the phonon nonequilibrium dynamics. We show how to stabilize stationary states exhibiting directional heat currents over arbitrary distance, despite the absence of thermal gradient and of direct coupling between the mechanical resonators.

Second-Harmonic Generation in Suspended AlGaAs Waveguides: A Comparative Study.

Due to adjustable modal birefringence, suspended AlGaAs optical waveguides with submicron transverse sections can support phase-matched frequency mixing in the whole material transparency range, even close to the material bandgap, by tuning the width-to-height ratio. Furthermore, their single-pass conversion efficiency is potentially huge, thanks to the extreme confinement of the interacting modes in the highly nonlinear and high-refractive-index core, with scattering losses lower than in selectively oxidized or quasi-phase-matched AlGaAs waveguides. Here we compare the performances of two types of suspended waveguides made of this material, designed for second-harmonic generation (SHG) in the telecom range: (a) a nanowire suspended in air by lateral tethers and (b) an ultrathin nanorib, made of a strip lying on a suspended membrane of the same material. Both devices have been fabricated from a 123 nm thick AlGaAs epitaxial layer and tested in terms of SHG efficiency, injection and propagation losses. Our results point out that the nanorib waveguide, which benefits from a far better mechanical robustness, performs comparably to the fully suspended nanowire and is well-suited for liquid sensing applications.

Optomechanical resonating probe for very high frequency sensing of atomic forces.

Atomic force spectroscopy and microscopy are invaluable tools to characterize nanostructures and biological systems. State-of-the-art experiments use resonant driving of mechanical probes, whose frequency reaches MHz in the fastest commercial instruments where cantilevers are driven at nanometer amplitude. Stiffer probes oscillating at tens of picometers provide a better access to short-range interactions, yielding images of molecular bonds, but they are little amenable to high-speed operation. Next-generation investigations demand combining very high frequency (>100 MHz) with deep sub-nanometer oscillation amplitude, in order to access faster (below microsecond) phenomena with molecular resolution. Here we introduce a resonating optomechanical atomic force probe operated fully optically at a frequency of 117 MHz, two decades above cantilevers, with a Brownian motion amplitude four orders below. Based on Silicon-On-Insulator technology, the very high frequency probe demonstrates single-pixel sensing of contact and non-contact interactions with sub-picometer amplitude, breaking open current limitations for faster and finer force spectroscopy.

High frequency optomechanical disk resonators in III-V ternary semiconductors: erratum.

An erratum is presented to correct for a typo in the appendix of the original article.

Shaping the Nonlinear Emission Pattern of a Dielectric Nanoantenna by Integrated Holographic Gratings.

We demonstrate the shaping of the second-harmonic (SH) radiation pattern from a single AlGaAs nanodisk antenna using coplanar holographic gratings. The SH radiation emitted from the antenna toward the-otherwise forbidden-normal direction can be effectively redirected by suitably shifting the phase of the grating pattern in the azimuthal direction. The use of such gratings allows increasing the SH power collection efficiency by 2 orders of magnitude with respect to an isolated antenna and demonstrates the possibility of intensity-tailoring for an arbitrary collection angle. Such reconstruction of the nonlinear emission from nanoscale antennas represents the first step toward the application of all-dielectric nanostructures for nonlinear holography.

Metal-dielectric hybrid nanoantennas for efficient frequency conversion at the anapole mode.

Background: Dielectric nanoantennas have recently emerged as an alternative solution to plasmonics for nonlinear light manipulation at the nanoscale, thanks to the magnetic and electric resonances, the strong nonlinearities, and the low ohmic losses characterizing high refractive-index materials in the visible/near-infrared (NIR) region of the spectrum. In this frame, AlGaAs nanoantennas demonstrated to be extremely efficient sources of second harmonic radiation. In particular, the nonlinear polarization of an optical system pumped at the anapole mode can be potentially boosted, due to both the strong dip in the scattering spectrum and the near-field enhancement, which are characteristic of this mode. Plasmonic nanostructures, on the other hand, remain the most promising solution to achieve strong local field confinement, especially in the NIR, where metals such as gold display relatively low losses. Results: We present a nonlinear hybrid antenna based on an AlGaAs nanopillar surrounded by a gold ring, which merges in a single platform the strong field confinement typically produced by plasmonic antennas with the high nonlinearity and low loss characteristics of dielectric nanoantennas. This platform allows enhancing the coupling of light to the nanopillar at coincidence with the anapole mode, hence boosting both second- and third-harmonic generation conversion efficiencies. More than one order of magnitude enhancement factors are measured for both processes with respect to the isolated structure. Conclusion: The present results reveal the possibility to achieve tuneable metamixers and higher resolution in nonlinear sensing and spectroscopy, by means of improved both pump coupling and emission efficiency due to the excitation of the anapole mode enhanced by the plasmonic nanoantenna.

Author Correction: Scalable high-precision tuning of photonic resonators by resonant cavity-enhanced photoelectrochemical etching.

The original version of this Article omitted the fourth author, Sara Ducci from Matériaux et Phénomènes Quantiques, Université Paris Diderot, CNRS UMR 7162, Sorbonne Paris-Cité, 10 rue Alice Domon et Léonie Duquet, Paris 75013, France. This mistake has been corrected in both the HTML and PDF versions of the Article.

Optomechanical terahertz detection with single meta-atom resonator.

Most of the common technologies for detecting terahertz photons (>1 THz) at room temperature rely on slow thermal devices. The realization of fast and sensitive detectors in this frequency range is indeed a notoriously difficult task. Here we propose a novel device consisting of a subwavelength terahertz meta-atom resonator, which integrates a nanomechanical element and allows energy exchange between the mechanical motion and the electromagnetic degrees of freedom. An incident terahertz wave thus produces a nanomechanical signal that can be read out optically with high precision. We exploit this concept to demonstrate a terahertz detector that operates at room temperature with high sensitivity and a much higher frequency response compared to standard detectors. Beyond the technological issue of terahertz detection, our architecture opens up new perspectives for fundamental science of light-matter interaction at terahertz frequencies, combining optomechanical approaches with semiconductor quantum heterostructures.

High frequency optomechanical disk resonators in III-V ternary semiconductors.

Optomechanical systems based on nanophotonics are advancing the field of precision motion measurement, quantum control and nanomechanical sensing. In this context III-V semiconductors offer original assets like the heteroepitaxial growth of optimized metamaterials for photon/phonon interactions. GaAs has already demonstrated high performances in optomechanics but suffers from two photon absorption (TPA) at the telecom wavelength, which can limit the cooperativity. Here, we investigate TPA-free III-V semiconductor materials for optomechanics applications: GaAs lattice-matched In0.5Ga0.5P and Al0.4Ga0.6As. We report on the fabrication and optical characterization of high frequency (500-700 MHz) optomechanical disks made out of these two materials, demonstrating high optical and mechanical Q in ambient conditions. Finally we achieve operating these new devices as laser-sustained optomechanical self-oscillators, and draw a first comparative study with existing GaAs systems.

Scalable high-precision tuning of photonic resonators by resonant cavity-enhanced photoelectrochemical etching.

Photonic lattices of mutually interacting indistinguishable cavities represent a cornerstone of collective phenomena in optics and could become important in advanced sensing or communication devices. The disorder induced by fabrication technologies has so far hindered the development of such resonant cavity architectures, while post-fabrication tuning methods have been limited by complexity and poor scalability. Here we present a new simple and scalable tuning method for ensembles of microphotonic and nanophotonic resonators, which enables their permanent collective spectral alignment. The method introduces an approach of cavity-enhanced photoelectrochemical etching in a fluid, a resonant process triggered by sub-bandgap light that allows for high selectivity and precision. The technique is presented on a gallium arsenide nanophotonic platform and illustrated by finely tuning one, two and up to five resonators. It opens the way to applications requiring large networks of identical resonators and their spectral referencing to external etalons.