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We report a compact, scalable, quantum photonic integrated circuit realised by combining multiple, tuneable InGaAs/GaAs quantum dot single photon sources with a silicon oxynitride waveguide circuit. Each waveguide in the circuit is addressed by a separate, electrically controlled quantum dot-containing diode. We show that the quantum dot emission from neighbouring diodes can be independently tuned to degeneracy using the Stark Effect and that the resulting photon streams are indistinguishable. This enables on-chip Hong-Ou-Mandel-type interference, as required for many photonic quantum information processing schemes. [ABSTRACT FROM AUTHOR]

We report the efficient coherent photon scattering from a semiconductor quantum dot embedded in a pillar microcavity. We show that a surface acoustic wave can periodically modulate the energy levels of the quantum dot but has a negligible effect on the cavity mode. The scattered narrow-band laser is converted into a pulsed single-photon stream, displaying an anti-bunching dip characteristic of single-photon emission. Multiple phonon sidebands are resolved in the emission spectrum, due to the absorption and emission of vibrational quanta in each scattering event. [ABSTRACT FROM AUTHOR]

We present a combined theoretical and experimental analysis of the optical properties of m-plane InGaN/GaN quantum wells. The sample was studied by photoluminescence and photoluminescence excitation spectroscopy at low temperature. The spectra show a large Stokes shift between the lowest exciton peak in the excitation spectra and the peak of the photoluminescence spectrum. This behavior is indicative of strong carrier localization effects. These experimental results are complemented by tight-binding calculations, accounting for random alloy fluctuations and Coulomb effects. The theoretical data explain the main features of the experimental spectra. Moreover, by comparison with calculations based on a virtual crystal approximation, the importance of carrier localization effects due to random alloy fluctuations is explicitly shown. [ABSTRACT FROM AUTHOR]

Fundamental to integrated photonic quantum computing is an on-chip method for routing and modulating quantum light emission. We demonstrate a hybrid integration platform consisting of arbitrarily designed waveguide circuits and single-photon sources. InAs quantum dots (QD) embedded in GaAs are bonded to a SiON waveguide chip such that the QD emission is coupled to the waveguide mode. The waveguides are SiON core embedded in a SiO2 cladding. A tuneable Mach Zehnder interferometer (MZI) modulates the emission between two output ports and can act as a path-encoded qubit preparation device. The single-photon nature of the emission was verified using the on-chip MZI as a beamsplitter in a Hanbury Brown and Twiss measurement. [ABSTRACT FROM AUTHOR]

We report the incorporation of a long-wavelength photovoltaic response (up to 8 μm) in a short-wavelength p-type GaAs heterojunction detector (with the activation energy of EA s 0.40 eV), operating at 80K. This wavelength-extended photovoltaic response is enabled by employing a non-symmetrical band alignment. The specific detectivity at 5 μm is obtained to be 3.5c1012 cm Hz1/2/W, an improvement by a factor of 105 over the detector without the wavelength extension. [ABSTRACT FROM AUTHOR]

We use internal photoemission spectroscopy to determine the conduction band offset of a type-II InAs/GaSb superlattice (T2SL) pBp photodetector to be 0.004 (±0.004) eV at 78 K, confirming its unipolar operation. It is also found that phonon-assisted hole transport through the B-region disables its two-color detection mode around 140 K. In addition, photoemission yield shows a reduction at about an energy of longitudinal-optical phonon above the threshold, confirming carrier-phonon scattering degradation on the photoresponse. These results may indicate a pathway for optimizing T2SL detectors in addition to current efforts in material growth, processing, substrate preparation, and device passivation. [ABSTRACT FROM AUTHOR]

Hole transitions from the heavy-hole (hh) to the light-hole (lh) band contributing to the 4–10 μm response range are reported on p-GaAs/AlGaAs detectors. The detectors show a spectral response up to 16.5 μm, operating up to a temperature of 330 K where the lh-hh response is superimposed on the free-carrier response. Two characteristic peaks observed between 5–7 μm are in good agreement with corresponding energy separations of the lh and hh bands and thus originated from lh-hh transitions. Results will be useful for designing multi-spectral detection which could be realized on a single p-GaAs structure. [ABSTRACT FROM AUTHOR]

The authors have developed a microcavity single-photon source based on a single quantum dot within a planar cavity in which wet oxidation of a high-aluminium content layer provides lateral confinement of both the photonic mode and the injection current. Lateral confinement of the optical mode in optically pumped structures produces a strong enhancement of the radiative decay rate. Using microcavity structures with doped contact layers, they demonstrate a single-photon emitting diode where current may be injected into a single dot. [ABSTRACT FROM AUTHOR]

The authors have fabricated pillar microcavity samples with Bragg mirrors consisting of alternate layers of GaAs and aluminum oxide. Compared to the more widely studied GaAs/AlAs micropillars, these mirrors can achieve higher reflectivities with fewer layer repeats and reduce the mode volume. The authors have studied a number of samples containing a low density of InGaAs/GaAs self-assembled quantum dots in a cavity and here report observation of a threefold enhancement in the radiative lifetime of a quantum dot exciton state due to the Purcell effect. [ABSTRACT FROM AUTHOR]

Degeneracy of the bright single exciton spin state is a prerequisite for the production of triggered polarization-entangled photon pairs from the biexciton decay of a quantum dot. Normally, however, the exciton spin states are split due to in-plane asymmetries. Here the authors demonstrate that the exciton splitting of an individual dot can be tuned through zero by thermal annealing. Repeated annealing blueshifts the exciton emission line of the dot, accompanied by a reduction and inversion in polarization splitting. Annealing is also demonstrated to control the detuning between the exciton and biexciton transitions in any selected dot. [ABSTRACT FROM AUTHOR]

Adiabatic and nonadiabatic nanofocusing of plasmons in tapered gap plasmon waveguides is analyzed using the finite-difference time-domain algorithm. Optimal adaptors between two different subwavelength waveguides and conditions for maximal local field enhancement are determined, investigated, and explained on the basis of dissipative and reflective losses in the taper. Nanofocusing of plasmons into a gap of ∼1 nm width with more than 20 times increase in the plasmon energy density is demonstrated in a silver-vacuum taper of ∼1 μm long. Comparison with the approximate theory based on the geometrical optics approximation is conducted. [ABSTRACT FROM AUTHOR]

We report on the use of an aperture in an aluminum oxide layer to restrict current injection into a single self-assembled InAs quantum dot from an ensemble of such dots within a large mesa. The insulating aperture is formed through the wet oxidation of a layer of AlAs. Under photoluminescence we observe that only one quantum dot in the ensemble exhibits a Stark shift, and that the same single dot is visible under electroluminescence. Autocorrelation measurements performed on the electroluminescence confirm that we are observing emission from a single quantum dot. [ABSTRACT FROM AUTHOR]

We report numerical analysis and experimental observation of two dimensionally localized plasmonic modes guided by a nanogap in a thin metal film. Dispersion, dissipation, and field structure of these modes are analyzed using the finite-difference time-domain algorithm. The experimental observation is conducted by the end-fire excitation of the proposed gap plasmon waveguides and detection of the generated modes using their edge scattering and charge coupled device camera imaging. Physical interpretation of the obtained results is presented and origins of the described modes are discussed. [ABSTRACT FROM AUTHOR]

We report numerical analysis and experimental observation of strongly localized plasmons guided by a triangular metal wedge. Dispersion and dissipation of such wedge plasmons are analyzed using the finite-difference time-domain algorithm. Experimental observation is conducted by the end-fire excitation and near-field detection of the predicted plasmons on a 40° silver nanowedge. Good agreement with the theoretically predicted propagation distances is demonstrated. Differences between the theoretical and experimental field distribution are explained by insufficient resolution of the near-field optical probe. [ABSTRACT FROM AUTHOR]

In this letter, we demonstrate the possibility of an effective nanoscale Fabry–Pérot interferometer in a subwavelength plasmonic waveguide in the form of a triangular groove on a metal surface, guiding channel plasmon-polaritons. The resonant cavity is formed by two semitransparent metal membranes (mirrors) placed into the groove. Effective filtering effect of the cavity is demonstrated, resulting in single-mode output from the cavity. Typical quality factor for the cavity of the resonant length is determined to be Q∼100 for the silver-vacuum structure with the 30° groove angle. Possible ways of increasing this factor are discussed. [ABSTRACT FROM AUTHOR]

We demonstrate that single-mode operation of a subwavelength plasmonic waveguide in the form of a V-groove on a metal surface can be achieved by adjusting the depth of the groove. Strongly localized channel plasmon-polaritons (CPPs) are shown to propagate in such waveguides. If the groove depth is close to the penetration depth of the fundamental CPP mode, then all higher modes are not supported by the structure, leaving only the fundamental mode propagating in the groove. In this case, propagation distances of fundamental mode ∼10 μm can easily be achieved together with strong subwavelength localization. [ABSTRACT FROM AUTHOR]

We demonstrate molecule-specific imaging of a chemically patterned self-assembled monolayer by IR-visible sum-frequency microscopy. The pattern on an Au substrate consists of microcontact printed 10 μm wide alkanethiolate stripes embedded in ω-carboxyalkanethiolate adsorbed from solution. We use both electronic and vibrational contrast mechanisms for a quantitative analysis of thiolate density and the coverage of the two molecular species. The evaluation of images taken at three different IR wavelengths suggests a substantial intermixing of the two thiolates occuring in the preparation procedure. © 2003 American Institute of Physics. [ABSTRACT FROM AUTHOR]

We demonstrate generation of a pulsed stream of electrically triggered single photons in resonance fluorescence, by applying high frequency electrical pulses to a single quantum dot in a p-i-n diode under resonant laser excitation. Single photon emission was verified, with the probability of multiple photon emission reduced to 2.8%. We show that despite the presence of charge noise in the emission spectrum of the dot, resonant excitation acts as a "filter" to generate narrow bandwidth photons. [ABSTRACT FROM AUTHOR]

In this work, we perform investigations of the competition between domain-wall pinning and attraction by antinotches and finite device borders. The conditions for optimal geometries, which can attain a stable domain-wall pinning, are presented. This allows the proposition of a three-terminal device based on domain-wall pinning. We obtain, with very small pulses of current applied parallel to the nanotrack, a fast motion of the domain-wall between antinotches. In addition to this, a swift stabilization of the pinned domain-wall is observed with a high percentage of orthogonal magnetization, enabling high magnetoresistive signal measurements. Thus, our proposed device is a promising magnetoresistive random access memory device with good scalability, duration, and high speed information storage. [ABSTRACT FROM AUTHOR]

Large scale fabrication using Complementary Metal Oxide Semiconductor compatible technology of semiconductor nanostructures that operate on the principles of quantum transport is an exciting possibility now due to the recent development of ultra-high mobility hole gases in epitaxial germanium grown on standard silicon substrates. We present here a ballistic transport study of patterned surface gates on strained Ge quantum wells with SiGe barriers, which confirms the quantum characteristics of the Ge heavy hole valence band structure in 1-dimension. Quantised conductance at multiples of 2e²/h is a universal feature of hole transport in Ge up to 10 × (2e²/h). The behaviour of ballistic plateaus with finite source-drain bias and applied magnetic field is elucidated. In addition, a reordering of the ground state is observed. [ABSTRACT FROM AUTHOR]

The initial proposal for scalable optical quantum computing required single photon sources, linear optical elements such as beamsplitters and phaseshifters, and photon detection. Here, we demonstrate a two qubit gate using indistinguishable photons from a quantum dot in a pillar microcavity. As the emitter, the optical circuitry, and the detectors are all semiconductor, this is a promising approach towards creating a fully integrated device for scalable quantum computing. [ABSTRACT FROM AUTHOR]

A correction to the article "Adiabatic and nonadiabatic nanofocusing of plasmons by tapered gap plasmon waveguides" that was previously published in the Journal "Applied Physics Letters" is presented.

We report the observation of a Purcell enhancement of the in-plane spontaneous emission rates of InAs self-assembled quantum dots coupled to a mode of a unidirectional photonic crystal waveguide fabricated in GaAs(001). Three-dimensional finite-difference time-domain simulations predict the existence of high quality-factor modes due to the slow light resonances of the waveguide. These modes have been observed experimentally with microphotoluminescence and produce enhanced in-plane emission when resonant with a quantum dot. [ABSTRACT FROM AUTHOR]

Quantum dot resonant tunneling diode single photon detector with independently defined absorption and sensing areas is demonstrated. The device, in which the tunneling is constricted to an aperture in an insulating layer in the emitter, shows electrical characteristics typical of high quality resonant tunneling diodes. A single photon detection efficiency of 2.1%±0.1% at 685 nm was measured corresponding to an internal quantum efficiency of 14%. The devices are simple to fabricate, robust, and show promise for large absorption area single photon detectors based on quantum dot structures. [ABSTRACT FROM AUTHOR]

Compact and electrically controllable on-chip sources of indistinguishable photons are desirable for the development of integrated quantum technologies. We demonstrate that two quantum dot light emitting diodes (LEDs) in close proximity on a single chip can function as a tunable, allelectric quantum light source. Light emitted by an electrically excited driving LED is used to excite quantum dots in the neighbouring diode. The wavelength of the quantum dot emission from the neighbouring driven diode is tuned via the quantum confined Stark effect. We also show that we can electrically tune the fine structure splitting. [ABSTRACT FROM AUTHOR]

Dye molecules bonded to a semiconductor surface could inject carriers to a band on photoexcitation. This process known as dye-sensitization is used for extending the sensitivity of silver halide emulsions. More recently, dye-sensitization has been adopted to devise solar cells. A near-infrared (NIR) sensitive heterojunction n-TiO2/D/p-CuSCN (where D denotes a NIR absorbing dye) is developed to examine the possibility of using dye-sensitization for IR detection. Although the responsivity is lower and response slow compared to silicon detectors, dye-sensitized detectors would be cost effective, especially for large area devices. They are operable at room temperature and have the advantage of insensitivity to noise induced by band-gap excitations (providing high specific detectivity of ∼1011). Furthermore, the spectral response can be adjusted by choosing the appropriate dye. [ABSTRACT FROM AUTHOR]

We present a demonstration of single photon emission from an entirely electrically driven resonant injection quantum dot device. We selectively measure the emission from a single dot in the ensemble by tuning the applied bias so as to induce resonant tunneling into the dot. Direct injection of carriers into the dot leads to a suppression of background light, allowing us to demonstrate single photon emission from a single dot with no spectral filtering. We study the effects limiting the linewidths of photons emitted from the device. [ABSTRACT FROM AUTHOR]