Results for "J. P. Finley"

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The Effect of Combined Magnetic Geometries on Thermally Driven Winds I: Interaction of Dipolar and Quadrupolar FieldsJul 13 2017Cool stars with outer convective envelopes are observed to have magnetic fields with a variety of geometries, which on large scales are dominated by a combination of the lowest order fields such as the dipole, quadrupole and octupole modes. Magnetised ... More
The Effect of Combined Magnetic Geometries on Thermally Driven Winds II: Dipolar, Quadrupolar and Octupolar TopologiesJan 23 2018During the lifetime of sun-like or low mass stars a significant amount of angular momentum is removed through magnetised stellar winds. This process is often assumed to be governed by the dipolar component of the magnetic field. However, observed magnetic ... More
Design Study of a Low Energy IACT Array for Ground-Based Gamma-Ray AstronomyAug 28 2007Recently, ground-based very high-energy (VHE) gamma-ray astronomy achieved a remarkable advancement in the development of the observational technique for the registration and study of gamma-ray emission above 100 GeV. Construction of telescopes of substantially ... More
The Effect of Combined Magnetic Geometries on Thermally Driven Winds II: Dipolar, Quadrupolar and Octupolar TopologiesJan 23 2018Mar 21 2018During the lifetime of sun-like or low mass stars a significant amount of angular momentum is removed through magnetised stellar winds. This process is often assumed to be governed by the dipolar component of the magnetic field. However, observed magnetic ... More
Lasing in Strong CouplingJun 02 2011An almost ideal thresholdless laser can be realized in the strong-coupling regime of light-matter interaction, with Poissonian fluctuations of the field at all pumping powers and all intensities of the field. This ideal scenario is thwarted by quantum ... More
Evidence for the Galactic X-ray Bulge IIJul 10 1998A mosaic of 5 \ros~PSPC pointed observations in the Galactic plane ($l\sim25^{\circ}$) reveals X-ray shadows in the $0.5-2.0$ keV band cast by distant molecular clouds. The observed on-cloud and off-cloud X-ray fluxes indicate that $\sim15$% and $\sim37$% ... More
The TeV Energy Spectrum of Mrk 421 Measured in A High Flaring StateAug 28 2007The BL Lac object (blazar) Mrk 421 was observed during its outburst in April 2004 with the Whipple 10 m telescope for a total of about 24.5 hours. The measured gamma-ray rate varied substantially over the range from 4 to 10 gamma's/min and eventually ... More
X-Ray Spectral Variability of Extreme BL Lac AGN H1426+428Oct 08 2003Between 7 March 2002 and 15 June 2002, intensive X-ray observations were carried out on the extreme BL Lac object H1426+428 with instruments on board the Rossi X-ray Timing Explorer (RXTE). These instruments provide measurements of H1426+428 in the crucial ... More
The Effect of Magnetic Variability on Stellar Angular Momentum Loss I: The Solar Wind Torque During Sunspot Cycles 23 & 24Jul 31 2018Aug 23 2018The rotational evolution of cool stars is governed by magnetised stellar winds which slow the stellar rotation during their main sequence lifetimes. Magnetic variability is commonly observed in Sun-like stars, and the changing strength and topology of ... More
The Effect of Magnetic Variability on Stellar Angular Momentum Loss II: The Sun, 61 Cygni A, $ε$ Eridani, $ξ$ Bootis A and $τ$ Bootis AMar 23 2019The magnetic fields of low-mass stars are observed to be variable on decadal timescales, ranging in behaviour from cyclic to stochastic. The changing strength and geometry of the magnetic field should modify the efficiency of angular momentum loss by ... More
The conversion of nonlocal one-body operators into local ones: The Slater potential revisitedJul 20 2004Oct 07 2004One-particle Schrodinger equations are considered, e.g., the Hartree--Fock equations, that contain a nonlocal operator, e.g., the Hartree--Fock exchange operator, where this operator depends on the one-particle density-matrix of a determinantal state. ... More
Developments for Reference--State One--Particle Density--Matrix TheoryFeb 12 2004Brueckner orbitals, and the density of the Brueckner reference-state, are shown to satify the same cusp condition -- involving the nuclear charges -- as natural- and Hartree--Fock-orbitals. Using the cusp condition, the density of a determinantal state ... More
Using the local density approximation and the LYP, BLYP, and B3LYP functionals within Reference--State One--Particle Density--Matrix TheoryAug 23 2003For closed-shell systems, the local density approximation (LDA) and the LYP, BLYP, and B3LYP functionals are shown to be compatible with reference-state one-particle density-matrix theory, where this recently introduced formalism is based on Brueckner-orbital ... More
Reference-State One-Particle Density-Matrix TheoryAug 14 2003A density-matrix formalism is developed based on the one-particle density-matrix of a single-determinantal reference-state. The v-representable problem does not appear in the proposed method, nor the need to introduce functionals defined by a constrained ... More
The Differential Virial Theorem with Gradient Formulas for the OperatorsAug 26 2016A gradient dependent formula is derived for the spinless one-particle density-matrix operator z from the differential virial theorem. A gradient dependent formula is also derived for a spinless one-particle density-matrix operator that can replace the ... More
Expressions for the Exchange Correlation Potential and Exchange Correlation Functional of Kohn--Sham Density Functional TheoryJun 12 2005The State--Specific Kohn--Sham Density Functional Theory [arXiv:physics/0506037] is used to derive the Kohn-Sham exchange-correlation potential $\vxc$ and exchange-correlation energy $\Eco$ as explicit functionals of $v_s$ and $\phi_1$, where $v_s$ is ... More
State-Specific Kohn-Sham Density Functional TheoryJun 04 2005Jun 07 2005A generalization of the Kohn--Sham approach is derived where the correlation-energy functional depends on the one-particle density matrix of noninteracting states and on the external potential from the interacting target-state. The one-particle equations ... More
Estabrook-Wahlquist Prolongations and Infinite-Dimensional AlgebrasDec 08 1995Detailed mappings between zero-curvture equations for prolongation structures of nonlinear pde's and Estabrook-Wahlquist algorithms for same are given. The differences are exemplified by studies of the sine-Gordon equation. An example where the prolongation ... More
The Robinson-Trautman Type III Prolongation Structure Contains K$_2$Jun 07 1995The minimal prolongation structure for the Robinson-Trautman equations of Petrov type III is shown to always include the infinite-dimensional, contragredient algebra, K$_2$, which is of infinite growth. Knowledge of faithful representations of this algebra ... More
Cavity versus dot emission in strongly coupled quantum dots-cavity systemsFeb 18 2011We discuss the spectral lineshapes of N quantum dots in strong coupling with the single mode of a microcavity. Nontrivial features are brought by detuning the emitters or probing the direct exciton emission spectrum. We describe dark states, quantum nonlinearities, ... More
Proper Motion of Pulsar B1800-21Jul 20 2006Oct 20 2006We report high angular resolution, multi-epoch radio observations of the young pulsar PSR B1800-21. Using two pairs of data sets, each pair spanning approximately a ten year period, we calculate the proper motion of the pulsar. We obtain a proper motion ... More
Asymptotic properties of the C-MetricMar 07 2010The aim of this article is to analyze the asymptotic properties of the C-metric, using a general method specified in work of Tafel and coworkers, [1], [2], [3]. By finding an appropriate conformal factor $\Omega$, it allows the investigation of the asymptotic ... More
Climbing the Jaynes-Cummings ladder by photon countingApr 18 2011Apr 19 2011We present a new method to observe direct experimental evidence of Jaynes--Cummings nonlinearities in a strongly dissipative cavity quantum electrodynamics system, where large losses compete with the strong light-matter interaction. This is a highly topical ... More
An Extended Radio Counterpart of TeV J2032+4130?Mar 01 2007We carried out a 5-pointing mosaic observation of TeV J2032+4130 at 1.4 and 4.8 GHz with the VLA in April of 2003. The analysis of the 4.8GHz data indicate weak wispy shell-like radio structure(s) which are at least partially non-thermal. The radio data ... More
A carrier relaxation bottleneck probed in single InGaAs quantum dots using integrated superconducting single photon detectorsJul 02 2014Aug 15 2014Using integrated superconducting single photon detectors we probe ultra-slow exciton capture and relaxation dynamics in single self-assembled InGaAs quantum dots embedded in a GaAs ridge waveguide. Time-resolved luminescence measurements performed with ... More
A connection between extremely strong Damped Lyman-alpha Systems and Lyman-alpha Emitting Galaxies at small impact parametersMar 17 2014We present a study of ~100 high redshift (z~2-4) extremely strong damped Lyman-alpha systems (ESDLA, with N(HI)>0.5x10^22 cm^-2) detected in quasar spectra from the Baryon Oscillation Spectroscopic Survey SDSS-III DR11. We study the neutral hydrogen, ... More
Infinite-Dimensional Estabrook-Wahlquist Prolongations for the sine-Gordon EquationJun 09 1995We are looking for the universal covering algebra for all symmetries of a given pde, using the sine-Gordon equation as a typical example for a non-evolution equation. For non-evolution equations, Estabrook-Wahlquist prolongation structures for non-local ... More
Non-linear two-photon resonance fluorescence on a single artificial atomNov 02 2015We report two-photon resonance fluorescence of an individual semiconductor artificial atom. By non-linearly driving a single quantum dot via a two-photon transition, we probe the linewidth of the two-photon processes and show that, similar to their single-photon ... More
Mutual Coupling of two Semiconductor Quantum Dots via an Optical Nanocavity ModeDec 18 2009Jul 12 2010We present an experimental and theoretical study of a system consisting of two spatially separated self-assembled InGaAs quantum dots strongly coupled to a single optical nanocavity mode. Due to their different size and compositional profiles, the two ... More
Recent advances in exciton based quantum information processing in quantum dot nanostructuresMay 30 2005Jul 08 2005Recent experimental developments in the field of semiconductor quantum dot spectroscopy will be discussed. First we report about single quantum dot exciton two-level systems and their coherent properties in terms of single qubit manipulations. In the ... More
Electrical control of spontaneous emission and strong coupling for a single quantum dotOct 16 2008Oct 24 2008We report the design, fabrication and optical investigation of electrically tunable single quantum dot - photonic crystal defect nanocavities operating in both the weak and strong coupling regimes of the light matter interaction. Unlike previous studies ... More
Highly Non-linear Excitonic Zeeman Spin-Splitting in Composition-Engineered Artificial AtomsDec 12 2011Non-linear Zeeman splitting of neutral excitons is observed in composition engineered In(x)Ga(1-x)As self-assembled quantum dots and its microscopic origin is explained. Eight-band k.p simulations, performed using realistic dot parameters extracted from ... More
Three stage decoherence dynamics of electron spin qubits in an optically active quantum dotOct 16 2014Apr 30 2015The control of discrete quantum states in solids and their use for quantum information processing is complicated by the lack of a detailed understanding of the mechanisms responsible for qubit decoherences. For spin qubits in semiconductor quantum dots, ... More
A Correlation between the Emission Intensity of Self-Assembled Germanium Islands and the Quality Factor of Silicon Photonic Crystal NanocavitiesMar 19 2011Mar 22 2011We present a comparative micro-photoluminescence study of the emission intensity of self-assembled germanium islands coupled to the resonator mode of two-dimensional silicon photonic crystal defect nanocavities. The emission intensity is investigated ... More
Controlled tunneling induced dephasing of Rabi rotations for ultra-high fidelity hole spin initializationApr 03 2015We report the sub-picosecond initialization of a single heavy hole spin in a self-assembled quantum dot with >98.5 % fidelity and without external magnetic field. Using an optically adressable charge and spin storage device we tailor the relative electron ... More
Emitters of $N$-photon bundlesJun 06 2013Oct 10 2013We propose a scheme based on the coherent excitation of a two-level system in a cavity to generate an ultrabright CW and focused source of quantum light that comes in groups (bundles) of $N$ photons, for an integer $N$ tunable with the frequency of the ... More
An Iterative Approach to Twisting and Diverging, Type N, Vacuum Einstein Equations: A (Third-Order) Resolution of Stephani's `Paradox'May 24 1996In 1993, a proof was published, within ``Classical and Quantum Gravity,'' that there are no regular solutions to the {\it linearized} version of the twisting, type-N, vacuum solutions of the Einstein field equations. While this proof is certainly correct, ... More
Fluctuation induced luminescence sidebands in the emission spectra of resonantly driven quantum dotsJul 30 2012We describe how complex fluctuations of the local environment of an optically active quantum dot can leave rich fingerprints in its emission spectrum. A new feature, termed "Fluctuation Induced Luminescence" (FIL), is observed to arise from extremely ... More
ASCA Detection of Pulsed X-ray Emission from PSR J0631+1036Apr 09 2001ASCA's long look at the 288 millisecond radio pulsar, PSR J0631+1036, reveals coherent X-ray pulsation from this source for the first time. The source was first detected in the serendipitous Einstein observation and later identified as a radio pulsar. ... More
Evidence for a very slow X-ray pulsar in 2S0114+650 from RXTE All-Sky Monitor ObservationsSep 16 1998Rossi X-ray Timing Explorer (RXTE) All-Sky Monitor (ASM) observations of the X-ray binary 2S0114+650 show modulations at periods close to both the optically derived orbital period (11.591 days) and proposed pulse period (~ 2.7 hr). The pulse period shows ... More
Coulomb mediated hybridization of excitons in artificial moleculesSep 29 2015We report the Coulomb mediated hybridization of excitonic states in an optically active, artificial quantum dot molecule. By probing the optical response of the artificial molecule as a function of the static electric field applied along the molecular ... More
Direct observation of metastable hot trions in an individual quantum dotOct 17 2011Magneto photoluminescence and excitation spectroscopy are used to probe the excited state spectrum of negatively charged trions in a InGaAs quantum dot. A single dot optical charging device allows us to selectively prepare specific few (1e, 2e) electron ... More
Shape control of QDs studied by cross-sectional scanning tunneling microscopyNov 15 2010In this cross-sectional scanning tunneling microscopy study we investigated various techniques to control the shape of self-assembled quantum dots (QDs) and wetting layers (WLs). The result shows that application of an indium flush during the growth of ... More
Chasing the Identification of ASCA Galactic Objects (ChIcAGO) - An X-ray Survey of Unidentified Sources in the Galactic Plane I: Source Sample and Initial ResultsMar 03 2014We present the Chasing the Identification of ASCA Galactic Objects (ChIcAGO) survey, which is designed to identify the unknown X-ray sources discovered during the ASCA Galactic Plane Survey (AGPS). Little is known about most of the AGPS sources, especially ... More
Independent dynamic acousto-mechanical and electrostatic control of individual quantum dots in a LiNbO$_{3}$-GaAs hybridOct 22 2014Dec 16 2014We demonstrate tuning of single quantum dot emission lines by the combined action of the dynamic acoustic field of a radio frequency surface acoustic wave and a static electric field. Both tuning parameters are set all-electrically in a LiNbO$_{3}$-GaAs ... More
Equations for Complex-Valued, Twisting, Type N, Vacuum Solutions, with one or two Killing/homothetic vectorsAug 23 2001HH-spaces, i.e., complex spacetimes, of Petrov type NxN are determined by a trio of pde's for two functions, lambda and a, of three independent variables (and also two gauge functions, chosen to be two of the independent variables if one prefers). As ... More
Linear and Non-linear Response of Lithographically Defined Plasmonic NanoantennasFeb 18 2015Feb 20 2015We present numerical studies, nano-fabrication and optical characterization of bowtie nanoantennas demonstrating their superior performance with respect to the electric field enhancement as compared to other Au nanoparticle shapes. For optimized parameters, ... More
The correlation energy as an explicit functional of the one-particle density matrix from a determinantal reference stateJun 24 2005Jun 28 2005Using an approach based on many body perturbation theory, the correlation energy $\cEco$ is expressed as an explicit functional of $\rho_1$, $v$, and $v_s$, where $\rho_1$ is the one-particle density matrix from the noninteracting, or reference, determinantal-state; ... More
Electrically probing photonic bandgap phenomena in contacted defect nanocavitiesSep 13 2007We demonstrate an electrically tunable two dimensional photonic crystal nanocavity containing InAs self assembled quantum dots. Photoluminescence and electroluminescence measurements are combined to probe the cavity mode structure and demonstrate a local ... More
Manipulation of the Spontaneous Emission Dynamics of Quantum Dots in 2D Photonic CrystalsJan 04 2005Apr 08 2005We demonstrate the ability to control the spontaneous emission dynamics of self-assembled quantum dots via the local density of optical modes in 2D-photonic crystals. We show that an incomplete 2D photonic bandgap is sufficient to significantly lengthen ... More
Direct measurement of plasmon propagation lengths on lithographically defined metallic waveguides on GaAsOct 19 2011We present optical investigations of rectangular surface plasmon polariton waveguides lithographically defined on GaAs substrates. The plasmon propagation length is directly determined using a confocal microscope, with independent polarization control ... More
Coplanar stripline antenna design for optically detected magnetic resonance on semiconductor quantum dotsFeb 14 2011We report on the development and testing of a coplanar stripline antenna that is designed for integration in a magneto-photoluminescence experiment to allow coherent control of individual electron spins confined in single self-assembled semiconductor ... More
Selective Optical Charge Generation, Storage and Readout in a Single Self Assembled Quantum DotDec 16 2008Jan 20 2009We report the investigation of a single quantum dot charge storage device. The device allows selective optical charging of a single dot with electrons, storage of these charges over timescales much longer than microseconds and reliable optical readout ... More
Evidence for an X-ray Emitting Galactic Bulge: Shadows Cast by Distant Molecular GasDec 04 1996A mosaic of 7 ROSAT PSPC pointed observations in the direction of (l,b ~ 10,0 deg) reveals deep X-ray shadows in the 0.5-2.0 keV band cast by dense molecular gas. The comparison between the observed on-cloud and off-cloud X-ray fluxes indicates that ~43% ... More
Limits to Quantum Gravity Effects from Observations of TeV Flares in Active GalaxiesOct 13 1998We have used data from the TeV gamma-ray flare associated with the active galaxy Markarian 421 observed on 15 May 1996 to place bounds on the possible energy-dependence of the speed of light in the context of an effective quantum gravitational energy ... More
Temporal Monitoring of Non-resonant Feeding of Semiconductor Nanocavity Modes by Quantum Dot Multiexciton TransitionsMar 15 2010We experimentally investigate the non-resonant feeding of photons into the optical mode of a zero dimensional nanocavity by quantum dot multiexciton transitions. Power dependent photoluminescence measurements reveal a super-linear power dependence of ... More
A Charge and Spin Readout Scheme For Single Self-Assembled Quantum DotsApr 02 2008We propose an all optical spin initialization and readout concept for single self assembled quantum dots and demonstrate its feasibility. Our approach is based on a gateable single dot photodiode structure that can be switched between charge and readout ... More
Highly efficient single photon emission from single quantum dots within a two-dimensional photonic bandgapAug 07 2007We report highly efficient single photon generation from InGaAs self-assembled quantum dots emitting within a two-dimensional photonic bandgap. A strongly suppressed multiphoton probability is obtained for single quantum dots in bulk GaAs and those emitting ... More
Strong electrically tunable exciton g-factors in an individual quantum dots due to hole orbital angular momentum quenchingAug 19 2010Aug 31 2010Strong electrically tunable exciton g-factors are observed in individual (Ga)InAs self-assembled quantum dots and the microscopic origin of the effect is explained. Realistic eight band k.p simulations quantitatively account for our observations, simultaneously ... More
Supernova Simulations and Strategies For the Dark Energy SurveyNov 08 2011Jul 12 2012We present an analysis of supernova light curves simulated for the upcoming Dark Energy Survey (DES) supernova search. The simulations employ a code suite that generates and fits realistic light curves in order to obtain distance modulus/redshift pairs ... More
Cavity-resonant excitation for efficient single photon generationMar 17 2008We present an efficiently pumped single photon source based on single quantum dots (QD) embedded in photonic crystal nanocavities. Resonant excitation of a QD via a higher order cavity mode results in a 100$\times$ reduced optical power at the saturation ... More
Efficient Spatial Redistribution of Quantum Dot Spontaneous Emission from 2D Photonic CrystalsJun 05 2007We investigate the modification of the spontaneous emission dynamics and external quantum efficiency for self-assembled InGaAs quantum dots coupled to extended and localised photonic states in GaAs 2D-photonic crystals. The 2D-photonic bandgap is shown ... More
Surface acoustic wave regulated single photon emission from a coupled quantum dot-nanocavity systemMay 16 2016Jul 11 2016A coupled quantum dot--nanocavity system in the weak coupling regime of cavity quantumelectrodynamics is dynamically tuned in and out of resonance by the coherent elastic field of a $f_{\rm SAW}\simeq800\,\mathrm{MHz}$ surface acoustic wave. When the ... More
Very High Energy Observations of PSR B1951+32Jun 15 1997PSR B1951+32 is a gamma-ray pulsar detected by the Energetic Gamma Ray Experiment Telescope (EGRET) and identified with the 39.5 ms radio pulsar in the supernova remnant CTB 80. The EGRET data shows no evidence for a spectral turnover. Here we report ... More
Column density distribution and cosmological mass density of neutral gas: Sloan Digital Sky Survey-III Data Release 9Oct 03 2012We present the first results from an ongoing survey for Damped Lyman-alpha systems (DLAs) in the spectra of z>2 quasars observed in the course of the Baryon Oscillation Spectroscopic Survey (BOSS), which is part of the Sloan Digital Sky Survey (SDSS) ... More
TeV Observations of the Variability and Spectrum of Markarian 501Jun 15 1997Markarian 501 is only the second extragalactic source to be detected with high statistical certainty at TeV energies; it is similar in many ways to Markarian 421. The Whipple Observatory gamma-ray telescope has been used to observe the AGN Markarian 501 ... More
Tev Observations of the Variability and Spectrum of Markarian 421Jun 13 1997Markarian 421 was the first extragalactic source to be detected with high statistical certainty at TeV energies. The Whipple Observatory gamma-ray telescope has been used to observe the Active Galactic Nucleus, Markarian 421 in 1996 and 1997. The rapid ... More
The Flux Variability of Markarian 501 in Very High Energy Gamma RaysMar 05 1999The BL Lacertae object Markarian 501 was identified as a source of gamma-ray emission at the Whipple Observatory in March 1995. Here we present a flux variability analysis on several times-scales of the 233 hour data set accumulated over 213 nights (from ... More
Surface plasmon resonance spectroscopy of single bowtie nano-antennas using a differential reflectivity methodFeb 05 2016We report on the structural and optical properties of individual bowtie nanoantennas both on glass and semiconducting GaAs substrates. The antennas on glass (GaAs) are shown to be of excellent quality and high uniformity reflected by narrow size distributions ... More
Galactic Compact Objects Section of the White Paper on the Status and Future of Ground-based TeV Gamma-ray AstronomyOct 03 2008This is a report on the findings of the Galactic compact objects working group for the white paper on the status and future of TeV gamma-ray astronomy. The white paper is an APS commissioned document, and the full version has also been released and can ... More
Integrated superconducting detectors on semiconductors for quantum optics applicationsJan 22 2016Semiconductor quantum photonic circuits can be used to efficiently generate, manipulate, route and exploit non-classical states of light for distributed photon based quantum information technologies. In this article, we review our recent achievements ... More
Return to the Kuiper Belt: launch opportunities from 2025 to 2040Oct 17 2018Preliminary spacecraft trajectories for 45 Kuiper Belt Objects (KBOs) and Pluto suitable for launch between 2025 and 2040 are presented. These 46 objects comprise all objects with H magnitude < 4.0 or which have received a name from the International ... More
Pulsed Rabi oscillations in quantum two-level systems: beyond the Area TheoremAug 17 2017Nov 03 2017The Area Theorem states that when a short optical pulse drives a quantum two-level system, it undergoes Rabi oscillations in the probability of scattering a single photon. In this work, we investigate the breakdown of the Area Theorem as both the pulse ... More
Optical study of lithographically defined, subwavelength plasmonic wires and their coupling to embedded quantum emittersJul 26 2013Jan 07 2014We present an optical investigation of surface plasmon polaritons propagating along nanoscale Au-wires, lithographically defined on GaAs substrates. A two-axis confocal microscope was used to perform spatially and polarization resolved measurements in ... More
The discovery of photospheric nickel in the hot DO white dwarf REJ0503-289Jan 11 2000We present the first evidence for the direct detection of nickel in the photosphere of the hot DO white dwarf REJ0503$-$289. While this element has been seen previously in the atmospheres of hot H-rich white dwarfs, this is one of the first similar discoveries ... More
Quasi-molecular Satellites of Lyman Beta in the Spectrum of the DA White Dwarf WOLF 1346Mar 20 1996We present new FUV/UV observations of the DA white dwarf Wolf 1346 obtained with the Hopkins Ultraviolet Telescope. The atmospheric parameters of this object are estimated from a fit of model atmospheres to several optical spectra to be Teff = 20000 K, ... More
Phonon-assisted transitions from quantum dot excitons to cavity photonsOct 20 2009For a single semiconductor quantum dot embedded in a microcavity, we theoretically and experimentally investigate phonon-assisted transitions between excitons and the cavity mode. Within the framework of the independent boson model we find that such transitions ... More
A Very High Energy Gamma-Ray Spectrum of 1ES 2344+514Aug 23 2005The BL Lacertae (BL Lac) object 1ES 2344+514 (1ES 2344), at a redshift of 0.044, was discovered as a source of very high energy (VHE) gamma rays by the Whipple Collaboration in 1995 \citep{2344Catanese98}. This detection was recently confirmed by the ... More
Multiwavelength Observations of a Flare from Markarian 501Jul 16 1997We present multiwavelength observations of the BL Lacertae object Markarian 501 (Mrk 501) in 1997 between April 8 and April 19. Evidence of correlated variability is seen in very high energy (VHE, E > 350 GeV) gamma-ray observations taken with the Whipple ... More
First Results from a Search for TeV Emission from BL LacsJun 13 1997Two active galactic nuclei have been detected at TeV energies using the atmospheric Cherenkov imaging technique. The Whipple Observatory gamma-ray telescope has been used to observe all the BL Lacertae objects in the northern hemisphere out to a redshift ... More
Search for TeV Counterparts in Gamma-Ray BurstsJun 13 1997Based on BACODINE network notification the Whipple Observatory gamma-ray telescope has been used to search for the delayed TeV counterpart to BATSE-detected gamma-ray bursts. In the fast slew mode, any point in the sky can be reached within two minutes ... More
A Search for TeV Emission from Unidentified Sources in the Galactic PlaneJun 17 1997The ~70 unidentified sources of the EGRET sky survey may be one of its most important legacies. The identification of these sources at other wavelengths is critical to understanding their nature. Many have flat spectra out to 10 GeV which, if extrapolated ... More
Constraints on Cosmic-Ray Origin Theories from TeV Gamma-Ray ObservationsJun 13 1997If supernova remnants (SNRs) are the sites of cosmic-ray acceleration, the associated nuclear interactions should result in observable fluxes of TeV gamma-rays from the nearest SNRs. Measurements of the gamma-ray flux from six nearby, radio-bright, SNRs ... More
Spectrum of TeV Gamma-Rays from the Crab NebulaJun 15 1997The Crab Nebula has become established as the standard candle for TeV gamma-ray astronomy using the atmospheric Cherenkov technique. No evidence for variability has been seen. The spectrum of gamma rays from the Crab Nebula has been measured in the energy ... More
Multiwavelength Observations of Markarian 421 in March 2001: an Unprecedented View on the X-ray/TeV Correlated VariabilityOct 22 2007Jun 16 2008(Abridged) We present a detailed analysis of week-long simultaneous observations of the blazar Mrk421 at 2-60 keV X-rays (RXTE) and TeV gamma-rays (Whipple and HEGRA) in 2001. The unprecedented quality of this dataset enables us to establish firmly the ... More
Electrical control of the exciton-biexciton splitting in a single self-assembled InGaAs quantum dotsSep 10 2010Jul 23 2011We report on single InGaAs quantum dots embedded in a lateral electric field device. By applying a voltage we tune the neutral exciton transition into resonance with the biexciton using the quantum confined Stark effect. The results are compared to theoretical ... More
Investigation of Non Resonant Dot - Cavity Coupling in Two Dimensional Photonic Crystal NanocavitiesFeb 14 2008We study the optical emission from single semiconductor quantum dots coupled to the optical modes of photonic crystal nanocavities. For dots that are both spectrally and spatially coupled, auto-correlation measurements reveal efficient single photon generation, ... More
All optical quantum control of a spin-quantum state and ultrafast transduction into an electric currentDec 12 2012The ability to control and exploit quantum coherence and entanglement drives research across many fields ranging from ultra-cold quantum gases to spin systems in condensed matter. Transcending different physical systems, optical approaches have proven ... More
Search for TeV Gamma-Rays from Shell-Type Supernova RemnantsJun 07 1999If cosmic rays with energies <100 TeV originate in the galaxy and are accelerated in shock waves in shell-type supernova remnants (SNRs), gamma-rays will be produced as the result of proton and electron interactions with the local interstellar medium, ... More
Deep MUSE observations in the HDFS. Morpho-kinematics of distant star-forming galaxies down to $10^8$M$_\odot$Dec 01 2015Sep 29 2016(Abridged) We make use of the deepest VLT/MUSE observations performed so far on the Hubble Deep Field South (HDFS) to characterize the low-mass (< $10^{10}$M$_\odot$) galaxy population at intermediate redshift. We identify a sample of 28 spatially-resolved ... More
Kinematics, Turbulence and Star Formation of z ~1 Strongly Lensed Galaxies seen with MUSEFeb 23 2018We analyse a sample of 8 highly magnified galaxies at redshift 0.6<z<1.5 observed with MUSE, exploring the resolved properties of these galaxies at sub-kiloparsec scales. Combining multi-band HST photometry and MUSE spectra, we derive the stellar mass, ... More
Anomalous Stark Shifts in Single Vertically Coupled Pairs of InGaAs Quantum DotsJul 02 2004Vertically coupled Stranski Krastanow QDs are predicted to exhibit strong tunnelling interactions that lead to the formation of hybridised states. We report the results of investigations into single pairs of coupled QDs in the presence of an electric ... More
A new method to epitaxially grow long-range ordered self-assembled InAs quantum dots on (110) GaAsMar 12 2004We report on a new approach for positioning of self-assembled InAs quantum dots on (110) GaAs with nanometer precision. By combining self-assembly of quantum dots with molecular beam epitaxy on in-situ cleaved surfaces (cleaved-edge overgrowth) we have ... More
Optical properties and interparticle coupling of plasmonic bowtie nanoantennas on a semiconducting substrateMay 13 2014We present the simulation, fabrication and optical characterization of plasmonic gold bowtie nanoantennas on a semiconducting GaAs substrate as geometrical parameters such as size, feed gap, height and polarization of the incident light are varied. The ... More
Direct Observation of Controlled Coupling in an Individual Quantum Dot MoleculeOct 08 2004Dec 21 2004We report the direct observation of quantum coupling in individual quantum dot molecules and its manipulation using static electric fields. A pronounced anti-crossing of different excitonic transitions is observed as the electric field is tuned. Comparison ... More
Direct observation of acoustic phonon mediated relaxation between coupled exciton states in a single quantum dot moleculeJul 03 2006We probe acoustic phonon mediated relaxation between tunnel coupled exciton states in an individual quantum dot molecule in which the inter-dot quantum coupling and energy separation between exciton states is continuously tuned using static electric field. ... More
The dielectric impact of layer distances on exciton and trion binding energies in van der Waals heterostructuresDec 15 2017The electronic and optical properties of monolayer transition-metal dichalcogenides (TMDs) and van der Waals heterostructures are strongly subject to their dielectric environment. In each layer the field lines of the Coulomb interaction are screened by ... More
Surface acoustic wave controlled charge dynamics in a thin InGaAs quantum wellMay 04 2012We experimentally study the optical emission of a thin quantum well and its dynamic modulation by a surface acoustic wave (SAW). We observe a characteristic transition of the modulation from one maximum to two maxima per SAW cycle as the acoustic power ... More
Direct Confirmation of the Asymmetry of the Cas A Supernova with Light EchoesMar 29 2010Feb 04 2011We report the first detection of asymmetry in a supernova (SN) photosphere based on SN light echo (LE) spectra of Cas A from the different perspectives of dust concentrations on its LE ellipsoid. New LEs are reported based on difference images, and optical ... More
Emission redistribution from a quantum dot-bowtie nanoantennaFeb 05 2016We present a combined experimental and simulation study of a single self-assembled InGaAs quantum dot coupled to a nearby ($\sim 25nm$) plasmonic antenna. Micro-photoluminescence spectroscopy shows a $\sim 2.4\times$ increase of intensity, which is attributed ... More