M. S. Skolnick

The University of Sheffield, Sheffield, England, United Kingdom

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Publications (657)1911.97 Total impact

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    ABSTRACT: Layered materials can be assembled vertically to fabricate a new class of van der Waals (VDW) heterostructures a few atomic layers thick, compatible with a wide range of substrates and opto-electronic device geometries, enabling new strategies for control of light-matter coupling. Here, we incorporate molybdenum diselenide/boron nitride (MoSe2/hBN) quantum wells (QWs) in a tun-able optical microcavity. Part-light-part-matter polariton eigenstates are observed as a result of the strong coupling between MoSe2 excitons and cavity photons, evidenced from a clear anticrossing between the neutral exciton and the cavity modes with a splitting of 20 meV for a single MoSe2 monolayer QW, enhanced to 29 meV in MoSe2/hBN/MoSe2 double-QWs. The splitting at resonance provides an estimate of the exciton radiative lifetime of 0.4 ps. Our results pave the way for room temperature polaritonic devices based on multiple-QW VDW heterostructures, where polari-ton condensation and electrical polariton injection through the incorporation of graphene contacts may be realised.
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    ABSTRACT: We report an extended family of spin textures in coexisting modes of zero-dimensional polariton condensates spatially confined in tunable open microcavity structures. The coupling between photon spin and angular momentum, which is enhanced in the open cavity structures, leads to new eigenstates of the polariton condensates carrying quantised spin vortices. Depending on the strength and anisotropy of the cavity confinement potential and the strength of the spin-orbit coupling, which can be tuned via the excitonic/photonic fractions, the condensate emissions exhibit either spin-vortex-like patterns or linear polarization, in good agreement with theoretical modelling.
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    ABSTRACT: We report an extended family of spin textures in coexisting modes of zero-dimensional polari-ton condensates spatially confined in tunable open microcavity structures. The coupling between photon spin and angular momentum, which is enhanced in the open cavity structures, leads to new eigenstates of the polariton condensates carrying quantised spin vortices. Depending on the strength and anisotropy of the cavity confinement potential and the strength of the spin-orbit coupling , which can be tuned via the excitonic/photonic fractions, the condensate emissions exhibit either spin-vortex-like patterns or linear polarization, in good agreement with theoretical modelling.
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    ABSTRACT: We demonstrate a new method to realize the population inversion of a single InGaAs/GaAs quantum dot excited by a laser pulse tuned within the neutral exciton phonon sideband. In contrast to the conventional method of inverting a two-level system by performing coherent Rabi oscillation, the inversion is achieved by rapid thermalization of the optically dressed states via incoherent phonon-assisted relaxation. A maximum exciton population of 0.67±0.06 is measured for a laser tuned 0.83 meV to higher energy. Furthermore, the phonon sideband is mapped using a two-color pump-probe technique, with its spectral form and magnitude in very good agreement with the result of path-integral calculations.
    Physical Review Letters 03/2015; 114:137401. DOI:10.1103/PhysRevLett.114.137401 · 7.73 Impact Factor
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    ABSTRACT: Interaction with nuclear spins leads to decoherence and information loss in solid-state electron-spin qubits. One particular, ineradicable source of electron decoherence arises from decoherence of the nuclear spin bath, driven by nuclear-nuclear dipolar interactions. Owing to its many-body nature nuclear decoherence is difficult to predict, especially for an important class of strained nanostructures where nuclear quadrupolar effects have a significant but largely unknown impact. Here, we report direct measurement of nuclear spin bath coherence in individual self-assembled InGaAs/GaAs quantum dots: spin-echo coherence times in the range 1.2-4.5 ms are found. Based on these values, we demonstrate that strain-induced quadrupolar interactions make nuclear spin fluctuations much slower compared with lattice-matched GaAs/AlGaAs structures. Our findings demonstrate that quadrupolar effects can potentially be used to engineer optically active III-V semiconductor spin-qubits with a nearly noise-free nuclear spin bath, previously achievable only in nuclear spin-0 semiconductors, where qubit network interconnection and scaling are challenging.
    Nature Communications 02/2015; 6:6348. DOI:10.1038/ncomms7348 · 10.74 Impact Factor
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    ABSTRACT: GaAs nanowires with elongated cross-section are formed using a catalyst-free growth technique. This is achieved by patterning elongated nanoscale openings within a silicon dioxide growth mask on a (111)B GaAs substrate. It is observed that MOVPE-grown vertical nanowires with cross-section elongated in the [2-1-1] and [-112] directions remain faithful to the geometry of the openings. An InGaAs quantum dot with weak radial confinement is realised within each nanowire by briefly introducing indium into the reactor during nanowire growth. Photoluminescence emission from an embedded nanowire quantum dot is strongly linearly polarized (typically > 90%) with the polarization direction coincident with the axis of elongation. Linearly polarized PL emission is a result of embedding the quantum dot in an anisotropic nanowire structure which supports a single strongly-confined, linearly polarized optical mode. This research provides a route to the bottom-up growth of linearly polarized single photon sources of interest for quantum information applications.
    Nano Letters 02/2015; 15(3). DOI:10.1021/nl503933n · 12.94 Impact Factor
  • Applied Physics Letters 01/2015; 106(2):021109. DOI:10.1063/1.4905907 · 3.52 Impact Factor
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    ABSTRACT: Resonantly-driven quantum emitters offer a very promising route to obtain highly coherent sources of single photons required for applications in quantum information processing (QIP). Realising this for on-chip scalable devices would be important for scientific advances and practical applications in the field of integrated quantum optics. Here we report on-chip quantum dot (QD) resonance fluorescence (RF) efficiently coupled into a single-mode waveguide, a key component of a photonic integrated circuit, with negligible resonant laser background and show that the QD coherence is enhanced by more than a factor of four compared to off-resonant excitation. Single-photon behaviour is confirmed under resonant excitation and fast fluctuating charge dynamics are revealed in autocorrelation g((2)) measurements. The potential for triggered operation is verified in pulsed RF. These results pave the way to a novel class of integrated quantum-optical devices for on-chip quantum information processing with embedded resonantly-driven quantum emitters.
    Nano Letters 11/2014; 14(12). DOI:10.1021/nl5032937 · 12.94 Impact Factor
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    ABSTRACT: New functionalities in nonlinear optics will require systems with giant optical nonlinearity as well as compatibility with photonic circuit fabrication techniques. Here we introduce a new platform based on strong light-matter coupling between waveguide photons and quantum-well excitons. On a sub-millimeter length scale we generate sub-picosecond bright temporal solitons at a pulse energy of only 0.5 pico-Joules. From this we deduce an unprecedented nonlinear refractive index 3 orders of magnitude larger than in any other ultrafast system. We study both temporal and spatio-temporal nonlinear effects and for the first time observe dark-bright spatio-temporal solitons. Theoretical modelling of soliton formation in the strongly coupled system confirms the experimental observations. These results show the promise of our system as a high speed, low power, integrated platform for physics and devices based on strong interactions between photons.
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    ABSTRACT: Quasi-two-dimensional (2D) films of layered metal-chalcogenides have attractive optoelectronic properties. However, photonic applications of thin films may be limited owing to weak light absorption and surface effects leading to reduced quantum yield. Integration of 2D films in optical microcavities will permit these limitations to be overcome owing to modified light coupling with the films. Here we present tunable microcavities with embedded monolayer MoS2 or few monolayer GaSe films. We observe significant modification of spectral and temporal properties of photoluminescence (PL): PL is emitted in spectrally narrow and wavelength-tunable cavity modes with quality factors up to 7400; PL life-time shortening by a factor of 10 is achieved, a consequence of Purcell enhancement of the spontaneous emission rate. This work has potential to pave the way to microcavity-enhanced light-emitting devices based on layered 2D materials and their heterostructures, and also opens possibilities for cavity QED in a new material system of van der Waals crystals.
    Nano Letters 08/2014; 14(12). DOI:10.1021/nl503312x · 12.94 Impact Factor
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    ABSTRACT: Semiconductor microcavities operating in the polaritonic regime are highly non-linear, high speed systems due to the unique half-light, half-matter nature of polaritons. Here, we report for the first time the observation of propagating multi-soliton polariton patterns consisting of multi-peak structures either along (x) or perpendicular to (y) the direction of propagation. Soliton arrays of up to 5 solitons are observed, with the number of solitons controlled by the size or power of the triggering laser pulse. The break-up along the x direction occurs due to interplay of bistability, negative effective mass and polariton-polariton scattering, while in the y direction the break-up results from nonlinear phase-dependent interactions of propagating fronts. We show the experimental results are in good agreement with numerical modelling. Our observations are a step towards ultrafast all-optical signal processing using sequences of solitons as bits of information.
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    ABSTRACT: We demonstrate the monolithic integration of an on-demand quantum emitter in the form of a single self-assembled InGaAs quantum dot with an air clad, free standing directional coupler acting as a beam-splitter for anti-bunched light.
    CLEO: QELS_Fundamental Science; 06/2014
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    ABSTRACT: We present a method to implement 3-dimensional polariton confinement with in-situ spectral tuning of the cavity mode. Our tunable microcavity is a hybrid system consisting of a bottom semiconductor distributed Bragg reflector (DBR) with a cavity containing quantum wells (QWs) grown on top and a dielectric concave DBR separated by a micrometer sized gap. Nanopositioners allow independent positioning of the two mirrors and the cavity mode energy can be tuned by controlling the distance between them. When close to resonance we observe a characteristic anticrossing between the cavity modes and the QW exciton demonstrating strong coupling. For the smallest radii of curvature concave mirrors of 5.6 $\mu$m and 7.5 $\mu$m real-space polariton imaging reveals submicron polariton confinement due to the hemispherical cavity geometry.
    Applied Physics Letters 05/2014; DOI:10.1063/1.4878504 · 3.52 Impact Factor
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    ABSTRACT: Advances in nanotechnology provide techniques for the realisation of integrated quantum-optical circuits for on-chip quantum information processing(QIP). The indistinguishable single photons, required for such devices can be generated by parametric down-conversion, or from quantum emitters such as colour centres and quantum dots(QDs). Among these, semiconductor QDs offer distinctive capabilities including on-demand operation, coherent control, frequency tuning and compatibility with semiconductor nanotechnology. Moreover, the coherence of QD photons can be significantly enhanced in resonance fluorescence(RF) approaching at its best the coherence of the excitation laser. However, the implementation of QD RF in scalable on-chip geometries remains challenging due to the need to suppress stray laser photons. Here we report on-chip QD RF coupled into a single-mode waveguide with negligible resonant laser background and show that the coherence is enhanced compared to off-resonant excitation. The results pave the way to a novel class of integrated quantum-optical devices for on-chip QIP with embedded resonantly-driven quantum emitters.
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    ABSTRACT: A fundamental component of an integrated quantum optical circuit is an on-chip beam-splitter operating at the single-photon level. Here we demonstrate the monolithic integration of an on-demand quantum emitter in the form of a single self-assembled InGaAs quantum dot (QD) with a compact (>10 um), air clad, free standing directional coupler acting as a beam-splitter for anti-bunched light. The device was tested by using single photons emitted by a QD embedded in one of the input arms of the device. We verified the single-photon nature of the QD signal by performing Hanbury Brown- Twiss (HBT) measurements and demonstrated single-photon beam splitting by cross-correlating the signal from the separate output ports of the directional coupler.
    Applied Physics Letters 04/2014; 104(23). DOI:10.1063/1.4883374 · 3.52 Impact Factor
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    ABSTRACT: Decoherence in quantum logic gates (qubits) due to interaction with the surrounding environment is a major obstacle to the practical realization of quantum information technologies. For solid state electron-spin qubits the interaction with nuclear spins is the main problem. One particular, neradicable source of electron decoherence arises from decoherence of the nuclear spin bath, driven by nuclear-nuclear dipolar interactions. Due to its many-body nature nuclear decoherence is difficult to predict, especially for an important class of strained nanostructures where nuclear quadrupolar effects have a significant but largely unknown impact. Here we report direct measurement of nuclear spin bath coherence in individual strained InGaAs/GaAs quantum dots: nuclear spin-echo coherence times in the range T2~1.2 - 4.5 ms are found. Based on these T2 values we demonstrate that quadrupolar interactions make nuclear fluctuations in strained quantum dots much slower compared to lattice matched GaAs/AlGaAs structures. Such fluctuation suppression is particularly strong for arsenic nuclei due to the effect of atomic disorder of gallium and indium alloying. Our findings demonstrate that quadrupolar effects can help to solve the long-standing challenge of designing a scalable hardware for quantum computation: III-V semiconductor spin-qubits can be engineered to have a noise-free nuclear spin bath (previously achievable only in nuclear spin-0 semiconductors, where qubit network interconnection and scaling is challenging).
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    ABSTRACT: We present a waveguide-coupled photonic crystal H1 cavity structure in which the orthogonal dipole modes couple to spatially separated photonic crystal waveguides. Coupling of each cavity mode to its respective waveguide with equal efficiency is achieved by adjusting the position and orientation of the waveguides. The behavior of the optimized device is experimentally verified for where the cavity mode splitting is larger and smaller than the cavity mode linewidth. In both cases, coupled Q-factors up to 1600 and contrast ratios up to 10 are achieved. This design may allow for spin state readout of a self-assembled quantum dot positioned at the cavity center or function as an ultra-fast optical switch operating at the single photon level.
    Optics Express 02/2014; 22(3):2376-85. DOI:10.1364/OE.22.002376 · 3.53 Impact Factor
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Publication Stats

12k Citations
1,911.97 Total Impact Points

Institutions

  • 1987–2015
    • The University of Sheffield
      • • Department of Physics and Astronomy
      • • Department of Electronic and Electrical Engineering
      Sheffield, England, United Kingdom
  • 2008
    • Universidad Autónoma de Madrid
      • Departamento de Física de Materiales
      Madrid, Madrid, Spain
  • 2007
    • University of North Carolina at Charlotte
      • Department of Physics & Optical Science
      Charlotte, NC, United States
    • University of Antioquia
      • Instituto de Física
      Santa Fe de Antioquia, Antioquia, Colombia
  • 2006–2007
    • University of Bristol
      • Department of Electrical and Electronic Engineering
      Bristol, ENG, United Kingdom
  • 2000–2006
    • University of Cambridge
      • Department of Physics: Cavendish Laboratory
      Cambridge, ENG, United Kingdom
  • 2005
    • University of Surrey
      • Advanced Technology Institute (ATI)
      Guildford, ENG, United Kingdom
  • 2001
    • Paul Sabatier University - Toulouse III
      Tolosa de Llenguadoc, Midi-Pyrénées, France
  • 1977–2001
    • University of Oxford
      • Department of Physics
      Oxford, England, United Kingdom
  • 1998–2000
    • University of Hull
      Kingston upon Hull, England, United Kingdom
    • University of Exeter
      Exeter, England, United Kingdom
  • 1990–2000
    • Imperial College London
      Londinium, England, United Kingdom
  • 1986–2000
    • University of Nottingham
      • School of Physics and Astronomy
      Nottigham, England, United Kingdom
  • 1994
    • University of Utah
      Salt Lake City, Utah, United States
  • 1991–1994
    • University of Wollongong
      City of Greater Wollongong, New South Wales, Australia
  • 1974
    • Laboratory of Plasma Physics
      Paliseau, Île-de-France, France