arXiv subjects

Aristide Lemaître

Publications and source records attributed to Aristide Lemaître.

At least 73 records · Page 4Linked to original sources

arXiv2017

Resonance fluorescence revival in a voltage-controlled semiconductor quantum dot

We demonstrate systematic resonance fluorescence recovery with near-unity emission efficiency in single quantum dots embedded in a charge-tunable device in a wave-guiding geometry. The quantum dot charge state is controlled by a gate voltage, through carrier tunneling from a close-lying Fermi sea, stabilizing the resonantly photocreated electron-hole pair. The electric field cancels out the charging/discharging mechanisms from nearby traps toward the quantum dots, responsible for the usually observed inhibition of the resonant fluorescence. Fourier transform spectroscopy as a function of the applied voltage shows a strong increase of the coherence time though not reaching the radiative limit. These charge controlled quantum dots act as quasi-perfect deterministic single-photon emitters, with one laser pulse converted into one emitted single photon.

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

Reducing phonon-induced decoherence in solid-state single-photon sources with cavity quantum electrodynamics

Solid-state emitters are excellent candidates for developing integrated sources of single photons. Yet, phonons degrade the photon indistinguishability both through pure dephasing of the zero-phonon line and through phonon-assisted emission. Here, we study theoretically and experimentally the indistinguishability of photons emitted by a semiconductor quantum dot in a microcavity as a function of temperature. We show that a large coupling to a high quality factor cavity can simultaneously reduce the effect of both phonon-induced sources of decoherence. It first limits the effect of pure dephasing on the zero phonon line with indistinguishabilities above $97\%$ up to $18$ K. Moreover, it efficiently redirects the phonon sidebands into the zero-phonon line and brings the indistinguishability of the full emission spectrum from $87\%$ (resp. $24\%$) without cavity effect to more than $99\%$ (resp. $76\%$) at $0$ K (resp. $20$ K). We provide guidelines for optimal cavity designs that further minimize the phonon-induced decoherence.

quant-ph↗

arXiv2016

Phase-controlled bistability of a dark soliton train in a polariton fluid

We use a one-dimensional polariton fluid in a semiconductor microcavity to explore the rich nonlinear dynamics of counter-propagating interacting Bose fluids. The intrinsically driven-dissipative nature of the polariton fluid allows to use resonant pumping to impose a phase twist across the fluid. When the polariton-polariton interaction energy becomes comparable to their kinetic energy, linear interference fringes transform into a train of solitons. A novel type of bistable behavior controlled by the phase twist across the fluid is experimentally evidenced.

cond-mat.mes-hall↗

arXiv2016

Origins and control of the polarization splitting in exciton-polaritons microwires

We report on the experimental investigation of the polarization-dependent energy splitting in the lower exciton-polariton branches of a 1D microcavity. The splitting observed for the lowest branch can reach up to 1 meV. It does not result from low temperature thermal constraints but from anisotropic mechanical internal strains induced by etching. Those strains remove the degeneracy both in the photonic ($δE_{\mathrm{ph}}$) and excitonic ($δE_{\mathrm{exc}}$) components of the polariton but also in the photon-exciton coupling ($δΩ$). Those three contributions are accurately infered from experimental data. It appears that the sign and magnitude of the polarization splitting as well as the linear polarization of the corresponding polariton eigenstates can be tuned through the bare exciton-photon detuning. Moreover, no dependence on the width of the wire (from 3 to 7 $\mathrmμ$m) is observed. We propose a mechanical model explaining the universality of those observations paving the way to the engineering of polarization eigenstates in microwires exciton-polaritons.

cond-mat.mes-hall↗

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

Orbital edge states in a photonic honeycomb lattice

We experimentally reveal the emergence of edge states in a photonic lattice with orbital bands. We use a two-dimensional honeycomb lattice of coupled micropillars whose bulk spectrum shows four gapless bands arising from the coupling of $p$-like photonic orbitals. We observe zero-energy edge states whose topological origin is similar to that of conventional edge states in graphene. Additionally, we report novel dispersive edge states that emerge not only in zigzag and bearded terminations, but also in armchair edges. The observations are reproduced by tight-binding and analytical calculations. Our work shows the potentiality of coupled micropillars in elucidating some of the electronic properties of emergent 2D materials with orbital bands.

cond-mat.mes-hall↗

arXiv2016

Multi-user quantum key distribution with entangled photons from an AlGaAs chip

In view of real world applications of quantum information technologies, the combination of miniature quantum resources with existing fibre networks is a crucial issue. Among such resources, on-chip entangled photon sources play a central role for applications spanning quantum communications, computing and metrology. Here, we use a semiconductor source of entangled photons operating at room temperature in conjunction with standard telecom components to demonstrate multi-user quantum key distribution, a core protocol for securing communications in quantum networks. The source consists of an AlGaAs chip emitting polarization entangled photon pairs over a large bandwidth in the main telecom band around 1550 nm without the use of any off-chip compensation or interferometric scheme; the photon pairs are directly launched into a dense wavelength division multiplexer (DWDM) and secret keys are distributed between several pairs of users communicating through different channels. We achieve a visibility measured after the DWDM of 87% and show long-distance key distribution using a 50-km standard telecom fibre link between two network users. These results illustrate a promising route to practical, resource-efficient implementations adapted to quantum network infrastructures.

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↗

arXiv2016

Stochastic precession of the polarization in a polariton laser

Microcavity polaritons in the lasing regime undergo a spontaneous symmetry breaking transition resulting in coherent emission with a well defined polarization. The order parameter is thus a vector describing both the laser global phase and polarization. Using an ultrafast single-shot detection technique we show that polariton lasing in GaAs-based microcavities presents a high degree of second order coherence ($g^{(2)}(τ=0) \approx 1$) above threshold, and that the initial polarization is stochastic, taking any possible direction in the Poincaré sphere (linear, elliptical or circular). Once the polarization direction is established, subsequent oscillations of the emission probability witness the presence of an intrinsic polarization splitting. Our results show the negligible role of polariton interactions in the total emission statistics and in the establishment of the initial polarization.

cond-mat.quant-gas↗

arXiv2016

Universal pinning energy barrier for driven domain walls in thin ferromagnetic films

We report a comparative study of magnetic field driven domain wall motion in thin films made of different magnetic materials for a wide range of field and temperature. The full thermally activated creep motion, observed below the depinning threshold, is shown to be described by a unique universal energy barrier function. Our findings should be relevant for other systems whose dynamics can be modeled by elastic interfaces moving on disordered energy landscapes.

cond-mat.mes-hall↗

arXiv2016

Strong reduction of the coercivity by a surface acoustic wave in an out-of-plane magnetized epilayer

Inverse magnetostriction is the effect by which magnetization can be changed upon application of stress/strain. A strain modulation may be created electrically by exciting interdigitated transducers to generate surface acoustic waves (SAWs). Hence SAWs appear as a possible route towards induction-free undulatory magnetic data manipulation. Here we demonstrate experimentally on an out-of-plane magnetostrictive layer a reduction of the coercive field of up to 60$\%$ by a SAW, over millimetric distances. A simple model shows that this spectacular effect can be partly explained by the periodic lowering of the strain-dependent domain nucleation energy by the SAW. This proof of concept was done on (Ga,Mn)(As,P), a magnetic semiconductor in which the out-of-plane magnetic anisotropy can be made very weak by epitaxial growth; it should guide material engineering for all-acoustic magnetization switching.

cond-mat.mtrl-sci↗

arXiv2015

Realization of an all optical exciton-polariton router

We report on the experimental realization of an all optical router for exciton-polaritons. This device is based on the design proposed by H. Flayac and I.G. Savenko [APL 103, 201105 (2013)], in which a zero-dimensional island is connected through tunnel barriers to two periodically modulated wires of different periods. Selective transmission of polaritons injected in the island, into either of the two wires, is achieved by tuning the energy of the island state across the band structure of the modulated wires. We show such polariton routing using an optical control beam which blueshifts the island quantum states thanks to polariton-exciton interactions. Operation of the device is demonstrated both under cw and pulsed operation.

cond-mat.mes-hall↗

arXiv2015

Direct measurement of coherent subterahertz acoustic phonons mean free path in GaAs

Phonon mean free path is generally inferred from the measurement of thermal conductivity and we are still lacking precise information on this quantity. Recent advances in the field of high frequency phonons transduction using semiconductor superlattices give the opportunity to fill this gap. We present experimental results on the attenuation of longitudinal acoustic phonons in GaAs in the frequency and temperature ranges 0.2-1THz and 10-80K respectively. Surprisingly, we observe a plateau, in the frequency dependence of the attenuation, above 0.4THz, that we ascribe to a breakdown of Herring processes.

cond-mat.mtrl-sci↗

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

Current Induced Fingering Instability in Magnetic Domain Walls

The shape instability of magnetic domain walls under current is investigated in a ferromagnetic (Ga,Mn)(As,P) film with perpendicular anisotropy. Domain wall motion is driven by the spin transfer torque mechanism. A current density gradient is found either to stabilize domains with walls perpendicular to current lines or to produce finger-like patterns, depending on the domain wall motion direction. The instability mechanism is shown to result from the non-adiabatic contribution of the spin transfer torque mechanism.

cond-mat.mtrl-sci↗

arXiv2014

Phonon-tuned bright single-photon source

Pure and bright single photon sources have recently been obtained by inserting solid-state emitters in photonic nanowires or microcavities. The cavity approach presents the attractive possibility to greatly increase the source operation frequency. However, it is perceived as technologically demanding because the emitter resonance must match the cavity resonance. Here we show that the spectral matching requirement is actually strongly lifted by the intrinsic coupling of the emitter to its environment. A single photon source consisting of a single InGaAs quantum dot inserted in a micropillar cavity is studied. Phonon coupling results in a large Purcell effect even when the quantum dot is detuned from the cavity resonance. The phonon-assisted cavity enhanced emission is shown to be a good single-photon source, with a brightness exceeding $40$ \% for a detuning range covering 15 cavity linewidths.

cond-mat.mes-hall↗

arXiv2014

Macroscopic Polarization Rotation Induced by a Single Spin

Solid-state spins hold many promises for quantum information processing. Entangling the polarization of a single photon to the state of a single spin would open new paradigms in quantum optics like delayed-photons entanglement, deterministic logic gates or fault-tolerant quantum computing. These perspectives rely on the possibility that a single spin induces a macroscopic rotation of a photon polarization. Such polarization rotations induced by single spins were recently observed, yet limited to a few 10-3 degrees, due to poor spin-photon coupling. Here we report the amplification by three orders of magnitude of the spin-photon interaction, using a cavity quantum electrodynamics device. A single hole spin trapped in a semiconductor quantum dot is deterministically coupled to a micropillar cavity. The cavity-enhanced coupling between the incoming photons and the solid-state spin results in a polarization rotation by \pm 6 degrees when the spin is optically initialized in either the up or down state. These results open the way towards a spin-based quantum network.

cond-mat.mes-hall↗