arXiv subjects

Ivan Favero

Publications and source records attributed to Ivan Favero.

At least 37 records · Page 2Linked to original sources

arXiv2018

Microscopic nanomechanical dissipation in gallium arsenide resonators

We report on a systematic study of nanomechanical dissipation in high-frequency (approximatively 300 MHz) gallium arsenide optomechanical disk resonators, in conditions where clamping and fluidic losses are negligible. Phonon-phonon interactions are shown to contribute with a loss background fading away at cryogenic temperatures (3 K). Atomic layer deposition of alumina at the surface modifies the quality factor of resonators, pointing towards the importance of surface dissipation. The temperature evolution is accurately fitted by two-level systems models, showing that nanomechanical dissipation in gallium arsenide resonators directly connects to their microscopic properties. Two-level systems, notably at surfaces, appear to rule the damping and fluctuations of such high-quality crystalline nanomechanical devices, at all temperatures from 3 to 300K.

cond-mat.mes-hall↗

arXiv2017

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.

physics.optics↗

arXiv2017

Optomechanical THz detection with a sub-wavelength resonator

The terahertz (THz) spectral domain offers a myriad of applications spanning chemical spectroscopy, medicine, security and imaging[1]. It has also recently become a playground for fundamental studies of light-matter interactions [2-6]. THz science and technology could benefit from optomechanical approaches, which harness the interaction of light with miniature mechanical resonators [7,8]. So far, optomechanics has mostly focused on the optical and microwave domains, leading to new types of quantum experiments [9-11] and to the development of optical-microwave converters [12-14]. Here we demonstrate an integrated meta-atom [15] THz resonator with a flexible part acting as a mechanical oscillator. In this device free space THz photons are collected by the resonator and induce high frequency currents and charges that, in turn, couple to the mechanical degrees of freedom. The resulting mechanical motion is read-out optically, allowing our device to function as a compact and efficient terahertz detector at room temperature. Furthermore the device operates at high modulation frequencies (>10MHz), well beyond the cut-off frequencies of Golay cells, pyroelectric detectors and cryogenic semiconductor bolometers [16,17]. Notably, our experiments unambiguously reveal an instantaneous THz detection mechanism arising from a nano-scale Coulomb interaction, with a Noise Equivalent Power that is potentially frequency independent. Alongside this effect, our compact geometry allows for an uncooled bolometric detection [18] with extremely short heat diffusion times (few microseconds) and high detectivity.

physics.optics↗

arXiv2016

Light-mediated cascaded locking of multiple nano-optomechanical oscillators

Collective phenomena emerging from non-linear interactions between multiple oscillators, such as synchronization and frequency locking, find applications in a wide variety of fields. Optomechanical resonators, which are intrinsically non-linear, combine the scientific assets of mechanical devices with the possibility of long distance controlled interactions enabled by travelling light. Here we demonstrate light-mediated frequency locking of three distant nano-optomechanical oscillators positioned in a cascaded configuration. The oscillators, integrated on a chip along a coupling waveguide, are optically driven with a single laser and oscillate at gigahertz frequency. Despite an initial frequency disorder of hundreds of kilohertz, the guided light locks them all with a clear transition in the optical output. The experimental results are described by Langevin equations, paving the way to scalable cascaded optomechanical configurations.

physics.optics↗

arXiv2016

Fully coupled hybrid cavity optomechanics: quantum interferences and correlations

We present a quantum theory for a fully coupled hybrid optomechanical system where all mutual couplings between a two-level atom, a confined photon mode and a mechanical oscillator mode are considered. In such a configuration, new quantum interference effects and correlations arise due to the interplay and competition between the different physical interactions. We present an analytical diagonalization of the related fully coupled Hamiltonian, showing the nature and energy spectra of the tripartite dressed excitations. We determine the driven-dissipative dynamics of such hybrid systems and study phonon blockade effects under resonant excitation. We also study the statistical properties of the photon emission obtained under incoherent pumping of the two-level atom, which is particularly relevant for experiments with solid-state two-level emitters.

quant-ph↗

arXiv2016

Surface-enhanced gallium arsenide photonic resonator with a quality factor of six million

Gallium Arsenide and related compound semiconductors lie at the heart of optoelectronics and integrated laser technologies. Shaped at the micro and nano-scale, they allow strong interaction with quantum dots and quantum wells, and promise to result in stunning devices. However gallium arsenide optical structures presently exhibit lower performances than their silicon-based counterparts, notably in nanophotonics where the surface plays a chief role. Here we report on advanced surface control of miniature gallium arsenide optical resonators, using two distinct techniques that produce permanent results. One leads to extend the lifetime of free-carriers and enhance luminescence, while the other strongly reduces surface absorption originating from mid-gap states and enables ultra-low optical dissipation devices. With such surface control, the quality factor of wavelength-sized optical disk resonators is observed to rise up to six million at telecom wavelength, greatly surpassing previous realizations and opening new prospects for Gallium Arsenide nanophotonics.

physics.optics↗

arXiv2015

High-precision spectral tuning of micro and nanophotonic cavities by resonantly enhanced photoelectrochemical etching

We present a simple method to tune optical micro- and nanocavities with picometer precision in the resonant wavelength, corresponding to an effective sub atomic monolayer control of the cavity dimension. This is obtained through resonant photo-electrochemical etching, with in-situ monitoring of the optical spectrum. We employ this technique to spectrally align an ensemble of resonant cavities in a permanent manner, overcoming the dimension variability resulting from current nanofabrication techniques. In a device containing several resonators, each is individually addressed and tuned, with no optical quality factor degradation. The technique is general and opens the way to multiple applications, such as the straightforward fabrication of networks of identical coupled resonators, or the tuning of chip-based cavities to external references.

physics.optics↗

arXiv2015

Integrated AlGaAs source of highly indistinguishable and energy-time entangled photons

The generation of nonclassical states of light in miniature chips is a crucial step towards practical implementations of future quantum technologies. Semiconductor materials are ideal to achieve extremely compact and massively parallel systems and several platforms are currently under development. In this context, spontaneous parametric down conversion in AlGaAs devices combines the advantages of room temperature operation, possibility of electrical injection and emission in the telecom band. Here we report on a chip-based AlGaAs source, producing indistinguishable and energy-time entangled photons with a brightness of $7.2\times10^6$ pairs/s and a signal-to-noise ratio of $141\pm12$. Indistinguishability between the photons is demonstrated via a Hong-Ou-Mandel experiment with a visibility of $89\pm3\%$, while energy-time entanglement is tested via a Franson interferometer leading to a value for the Bell parameter $ S=2.70\pm0.10$.

quant-ph↗

arXiv2015

Origin of optical losses in gallium arsenide disk whispering gallery resonators

Whispering gallery modes in GaAs disk resonators reach half a million of optical quality factor. These high Qs remain still well below the ultimate design limit set by bending losses. Here we investigate the origin of residual optical dissipation in these devices. A Transmission Electron Microscope analysis is combined with an improved Volume Current Method to precisely quantify optical scattering losses by roughness and waviness of the structures, and gauge their importance relative to intrinsic material and radiation losses. The analysis also provides a qualitative description of the surface reconstruction layer, whose optical absorption is then revealed by comparing spectroscopy experiments in air and in different liquids. Other linear and nonlinear optical loss channels in the disks are evaluated likewise. Routes are given to further improve the performances of these miniature GaAs cavities.

physics.optics↗

arXiv2014

Improved optomechanical disk resonator sitting on a pedestal mechanical shield

We experimentally demonstrate the controlled enhancement of the mechanical quality factor Q of GaAs disk optomechanical resonators. Disks vibrating at 1.3 GHz with a mechanical shield integrated in their pedestal show a Q improvement by a factor 10 to 16. The structure is modeled numerically and different modes of vibration are observed, which shed light on the Q enhancement mechanism. An optimized double-disk geometry is presented that promises Q above the million for a large parameter range.

cond-mat.mes-hall↗

arXiv2014

Photoelastic coupling in gallium arsenide optomechanical disk resonators

We analyze the magnitude of the radiation pressure and electrostrictive stresses exerted by light confined inside GaAs semiconductor WGM optomechanical disk resonators, through analytical and numerical means, and find the electrostrictive force to be of prime importance. We investigate the geometric and photoelastic optomechanical coupling resulting respectively from the deformation of the disk boundary and from the strain-induced refractive index changes in the material, for various mechanical modes of the disks. Photoelastic optomechanical coupling is shown to be a predominant coupling mechanism for certain disk dimensions and mechanical modes, leading to total coupling g$_{om}$ and g$_0$ reaching respectively 3 THz/nm and 4 MHz. Finally, we point towards ways to maximize the photoelastic coupling in GaAs disk resonators, and we provide some upper bounds for its value in various geometries.

physics.optics↗

arXiv2013

An electrically injected photon-pair source at room temperature

One of the main challenges for future quantum information technologies is miniaturization and integration of high performance components in a single chip. In this context, electrically driven sources of non-classical states of light have a clear advantage over optically driven ones. Here we demonstrate the first electrically driven semiconductor source of photon pairs working at room temperature and telecom wavelength. The device is based on type-II intracavity Spontaneous Parametric Down-Conversion in an AlGaAs laser diode and generates pairs at 1.57 $μ$m. Time-correlation measurements of the emitted pairs give an internal generation efficiency of $7 \times 10^{-11}$ pairs/injected electron. The capability of our platform to support generation, manipulation and detection of photons opens the way to the demonstration of massively parallel systems for complex quantum operations.

quant-ph↗

arXiv2013

Direct high-resolution characterization of quantum correlations via classical measurements

Quantum optics plays a central role in the study of fundamental concepts in quantum mechanics, and in the development of new technological applications. Typical experiments employ non-classical light, such as entangled photons, generated by parametric processes. The standard characterization of the sources by quantum tomography, which relies on detecting the pairs themselves and thus requires single photon detectors, limits both measurement speed and accuracy. Here we show that the spectral characterization of the quantum correlations generated by two-photon sources can be directly performed classically with an unprecedented spectral resolution. This streamlined technique has the potential to speed up design and testing of massively parallel integrated sources by providing a fast and reliable quality control procedure. Adapting our method to explore other degrees of freedom would allow the complete characterization of biphoton states generated by parametric processes.

quant-ph↗

arXiv2013

Single Polariton Optomechanics

This paper investigates a novel hybrid cavity QED-optomechanics situation. We solve the Hamiltonian problem of a cavity coupled both to a two-level atom via a Jaynes-Cummings coupling and to a mechanical motion via radiation pressure coupling. The atom-cavity polariton number operator commutes with the total Hamiltonian leading to an exact analytical solution involving tripartite atom-cavity-mechanics polarons. Under optical pumping of polaronic transitions the system displays unusual atom-assisted cooling and amplification of mechanical motion. We demonstrate the possibility to obtain enhanced optomechanical cooling at the single polariton level, strong bunching of phonons, and describe the peculiar quantum noise statistics of mechanical motion in the single polariton amplification limit.

quant-ph↗

arXiv2013

Bell states generation on a III-V semiconductor chip at room temperature

We demonstrate the generation of polarization-entangled photon pairs at room temperature and telecom wavelength in a AlGaAs semiconductor waveguide. The source is based on spontaneous parametric down conversion with a counterpropagating phase-matching scheme. The quality of the two-photon state is assessed by the reconstruction of the density matrix giving a raw fidelity to a Bell state of 0.83; a theoretical model, taking into account the experimental parameters, provides ways to understand and control the amount of entanglement. Its compatibility with electrical injection, together with the high versatility of the generated two-photon state, make this source an attractive candidate for completely integrated quantum photonics devices.

quant-ph↗

arXiv2013

Ultrahigh Q-Frequency product for optomechanical disk resonators with a mechanical shield

We report on optomechanical GaAs disk resonators with ultrahigh quality factor - frequency product Qf. Disks standing on a simple pedestal exhibit GHz breathing modes attaining a Qf of 10^13 measured under vacuum at cryogenic temperature. Clamping losses are found to be the dominant source of dissipation in this configuration. A new type of disk resonator integrating a shield within the pedestal is then proposed and its working principles and performances investigated by numerical simulations. For dimensions compatible with fabrication constraints, the clamping-loss-limited Q reaches 10^7-10^9 corresponding to Qf of 10^16-10^18. This shielded pedestal approach applies to any heterostructure presenting an acoustic mismatch.

cond-mat.mes-hall↗

arXiv2013

Damping and non-linearity of a levitating magnet in rotation above a superconductor

We study the dissipation of moving magnets in levitation above a superconductor. The rotation motion is analyzed using optical tracking techniques. It displays a remarkable regularity together with long damping time up to several hours. The magnetic contribution to the damping is investigated in detail by comparing 14 distinct magnetic configurations, and points towards amplitude-dependent dissipation mechanisms. The non-linear dynamics of the mechanical rotation motion is also revealed and described with an effective Duffing model. The obtained picture of the coupling of levitating magnets to their environment sheds light on their potential as ultra-low dissipation mechanical oscillators for high precision physics.

cond-mat.mes-hall↗

arXiv2011

Cavity nano-optomechanics: a nanomechanical system in a high finesse optical cavity

The coupling of mechanical oscillators with light has seen a recent surge of interest, as recent reviews report.[1, 2] This coupling is enhanced when confining light in an optical cavity where the mechanical oscillator is integrated as back- mirror or movable wall. At the nano-scale, the optomechanical coupling increases further thanks to a smaller optomechanical interaction volume and reduced mass of the mechanical oscillator. In view of realizing such cavity nano- optomechanics experiments, a scheme was proposed where a sub-wavelength sized nanomechanical oscillator is coupled to a high finesse optical microcavity.[3] Here we present such an experiment involving a single nanomechanical rod precisely positioned into the confined mode of a miniature Fabry-Pérot cavity.[4] We describe the employed stabilized cavity set-up and related finesse measurements. We proceed characterizing the nanorod vibration properties using ultrasonic piezo-actuation methods. Using the optical cavity as a transducer of nanomechanical motion, we monitor optically the piezo-driven nanorod vibration. On top of extending cavity quantum electrodynamics concepts to nanomechanical systems, cavity nano-optomechanics should advance into precision displacement measurements near the standard quantum limit [5], investigation of mechanical systems in their quantum regime, non-linear dynamics [6] and sensing applications.

physics.optics↗