Gerald S. Buller

Heriot-Watt University, Edinburgh, Scotland, United Kingdom

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Publications (172)268.07 Total impact

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    ABSTRACT: http://www.springer.com/chemistry/analytical+chemistry/book/978-3-319-15635-4 This volume focuses on Time-Correlated Single Photon Counting (TCSPC), a powerful tool allowing luminescence lifetime measurements to be made with high temporal resolution, even on single molecules. Combining spectrum and lifetime provides a “fingerprint” for identifying such molecules in the presence of a background. Used together with confocal detection, this permits single-molecule spectroscopy and microscopy in addition to ensemble measurements, opening up an enormous range of hot life science applications such as fluorescence lifetime imaging (FLIM) and measurement of Förster Resonant Energy Transfer (FRET) for the investigation of protein folding and interaction. Several technology-related chapters present both the basics and current state-of-the-art, in particular of TCSPC electronics, photon detectors and lasers. The remaining chapters cover a broad range of applications and methodologies for experiments and data analysis, including the life sciences, defect centers in diamonds, super-resolution microscopy, and optical tomography. The chapters detailing new options arising from the combination of classic TCSPC and fluorescence lifetime with methods based on intensity fluctuation represent a particularly unique highlight. Keywords » Antibunching - Coincidence correlation - Diamond defect centers - FCS - FLIM - FRET - Fluorescence correlation spectroscopy - Fluorescence lifetime - Optical tomography - Single molecule spectroscopy - Single photon detectors - TCSPC - Time interval analysis - Time-correlated single photon counting
    Springer Series on Fluorescence, Vol. 15 edited by Peter Kapusta, Michael Wahl, Rainer Erdmann, 06/2015; Springer, Part of Springer Science+Business Media, Link: http://www.springer.com/chemistry/analytical+chemistry/book/978-3-319-15635-4., ISBN: 978-3-319-15636-1, 978-3-319-15635-4
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    ABSTRACT: Link: http://www.springer.com/chemistry/analytical+chemistry/book/978-3-319-15635-4 This volume focuses on Time-Correlated Single Photon Counting (TCSPC), a powerful tool allowing luminescence lifetime measurements to be made with high temporal resolution, even on single molecules. Combining spectrum and lifetime provides a “fingerprint” for identifying such molecules in the presence of a background. Used together with confocal detection, this permits single-molecule spectroscopy and microscopy in addition to ensemble measurements, opening up an enormous range of hot life science applications such as fluorescence lifetime imaging (FLIM) and measurement of Förster Resonant Energy Transfer (FRET) for the investigation of protein folding and interaction. Several technology-related chapters present both the basics and current state-of-the-art, in particular of TCSPC electronics, photon detectors and lasers. The remaining chapters cover a broad range of applications and methodologies for experiments and data analysis, including the life sciences, defect centers in diamonds, super-resolution microscopy, and optical tomography. The chapters detailing new options arising from the combination of classic TCSPC and fluorescence lifetime with methods based on intensity fluctuation represent a particularly unique highlight. Keywords » Antibunchng - Coincidence correlation - Diamond defect centers - FCS - FLIM - FRET - Fluorescence correlation spectroscopy - Fluorescence lifetime - Optical tomography - Single molecule spectroscopy - Single photon detectors - TCSPC - Time interval analysis - Time-correlated single photon counting
    Springer Series on Fluorescence, Vol. 15 edited by Peter Kapusta, Michael Wahl, Rainer Erdmann, 06/2015; Springer, Part of Springer Science+Business Media, Link: http://www.springer.com/chemistry/analytical+chemistry/book/978-3-319-15635-4., ISBN: 978-3-319-15636-1, 978-3-319-15635-4
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    ABSTRACT: The ability to record images with extreme temporal resolution enables a diverse range of applications, such as fluorescence lifetime imaging, time-of-flight depth imaging and characterization of ultrafast processes. Recently, ultrafast imaging schemes have emerged, which require either long acquisition times or raster scanning and have a requirement for sufficient signal that can only be achieved when light is reflected off an object or diffused by a strongly scattering medium. Here we present a demonstration of the potential of single-photon detector arrays for visualization and rapid characterization of events evolving on picosecond time scales. The single-photon sensitivity, temporal resolution and full-field imaging capability enables the observation of light-in-flight in air, as well as the measurement of laser-induced plasma formation and dynamics in its natural environment. The extreme sensitivity and short acquisition times pave the way for real-time imaging of ultrafast processes or visualization and tracking of objects hidden from view.
    Nature Communications 01/2015; 6:6021. DOI:10.1038/ncomms7021 · 10.74 Impact Factor
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    ABSTRACT: Multispectral light detection and ranging (LiDAR) has the potential to recover structural and physiological data from arboreal samples and, by extension, from forest canopies when deployed on aerial or space platforms. In this paper, we describe the design and evaluation of a prototype multispectral LiDAR system and demonstrate the measurement of leaf and bark area and abundance profiles using a series of experiments on tree samples “viewed from above” by tilting living conifers such that the apex is directed on the viewing axis. As the complete recovery of all structural and physiological parameters is ill posed with a restricted set of four wavelengths, we used leaf and bark spectra measured in the laboratory to constrain parameter inversion by an extended reversible jump Markov chain Monte Carlo algorithm. However, we also show in a separate experiment how the multispectral LiDAR can recover directly a profile of Normalized Difference Vegetation Index (NDVI), which is verified against the laboratory spectral measurements. Our work shows the potential of multispectral LiDAR to recover both structural and physiological data and also highlights the fine spatial resolution that can be achieved with time-correlated single-photon counting.
    IEEE Transactions on Geoscience and Remote Sensing 07/2014; 52(8). DOI:10.1109/TGRS.2013.2285942 · 2.93 Impact Factor
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    ABSTRACT: Digital signatures are widely used to provide security for electronic communications, for example, in financial transactions and electronic mail. Currently used classical digital signature schemes, however, only offer security relying on unproven computational assumptions. In contrast, quantum digital signatures offer information-theoretic security based on laws of quantum mechanics. Here, security against forging relies on the impossibility of perfectly distinguishing between nonorthogonal quantum states. A serious drawback of previous quantum digital signature schemes is that they require long-term quantum memory, making them impractical at present. We present the first realization of a scheme that does not need quantum memory and which also uses only standard linear optical components and photodetectors. In our realization, the recipients measure the distributed quantum signature states using a new type of quantum measurement, quantum state elimination. This significantly advances quantum digital signatures as a quantum technology with potential for real applications.
    Physical Review Letters 07/2014; 113(4):040502. · 7.73 Impact Factor
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    ABSTRACT: The response of cells to changes in their physico-chemical micro-environment is essential to their survival. For example, bacterial magnetotaxis uses the Earth's magnetic field together with chemical sensing to help microorganisms move towards favoured habitats. The studies of such complex responses are lacking a method that permits the simultaneous mapping of the chemical environment and the response of the organisms, and the ability to generate a controlled physiological magnetic field. We have thus developed a multi-modal microscopy platform that fulfils these requirements. Using simultaneous fluorescence and high-speed imaging in conjunction with diffusion and aerotactic models, we characterized the magneto- aerotaxis of Magnetospirillum gryphiswaldense. We assessed the influence of the magnetic field (orientation; strength) on the formation and the dynamic of a micro-aerotactic band (size, dynamic, position). As previously described by models of magnetotaxis, the application of a magnetic field pointing towards the anoxic zone of an oxygen gradient results in an enhanced aerotaxis even down to Earth's magnetic field strength. We found that neither a ten-fold increase of the field strength nor a tilt of 45° resulted in a significant change of the aerotactic efficiency. However, when the field strength is zeroed or when the field angle is tilted to 90°, the magneto-aerotaxis efficiency is drastically reduced. The classical model of magneto-aerotaxis assumes a response proportional to the cosine of the angle difference between the directions of the oxygen gradient and that of the magnetic field. Our experimental evidence however shows that this behaviour is more complex than assumed in this model, thus opening up new avenues for research.
    PLoS ONE 07/2014; 9(7):e101150. DOI:10.1371/journal.pone.0101150 · 3.53 Impact Factor
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    ABSTRACT: SPAD structures have been grown by RP-CVD and shown to have: excellent crystallinity, with low TDD; a smooth surface, suitable for device incorporation; and sharp doping profiles required to maximize performance. Device measurements have produced the highest SPDE of any Ge on Si SPAD recorded.
    2014 7th International Silicon-Germanium Technology and Device Meeting (ISTDM); 06/2014
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    ABSTRACT: Quantum optical amplification that beats the noise addition limit for deterministic amplifiers has been realized experimentally using several different nondeterministic protocols. These schemes either require single-photon sources, or operate by noise addition and photon subtraction. Here we present an experimental demonstration of a protocol that allows nondeterministic amplification of known sets of coherent states with high gain and high fidelity. The experimental system employs the two mature quantum optical technologies of state comparison and photon subtraction and does not rely on elaborate quantum resources such as single-photon sources. The use of coherent states rather than single photons allows for an increased rate of amplification and a less complex photon source. Furthermore it means that the amplification is not restricted to low amplitude states. With respect to the two key parameters, fidelity and amplified state production rate, we demonstrate, without the use of quantum resources, significant improvements over previous experimental implementations.
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    ABSTRACT: ZnSe and CdSe layers have been grown on InAs substrates using molecular beam epitaxy (MBE) without the need for a III-V and II-VI dual chamber system. This paper reports on the optimisation of a chemical oxide removal process using sulphur passivation. This removes the need for conventional in vacuo oxide removal under As overpressure that is used to prevent the formation of high densities of In droplets. X-ray and photoluminescence characterisation of the samples confirms single crystal growth. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
    physica status solidi (c) 03/2014; DOI:10.1002/pssc.201300624
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    ABSTRACT: Digital signatures are widely used to provide security for electronic communications, for example in financial transactions and electronic mail. Currently used classical digital signature schemes, however, only offer security relying on unproven computational assumptions. In contrast, quantum digital signatures (QDS) offer information-theoretic security based on laws of quantum mechanics (e.g. Gottesman and Chuang 2001). Here, security against forging relies on the impossibility of perfectly distinguishing between non-orthogonal quantum states. A serious drawback of previous QDS schemes is however that they require long-term quantum memory, making them unfeasible in practice. We present the first realisation of a scheme (Dunjko et al 2013) that does not need quantum memory, and which also uses only standard linear optical components and photodetectors. To achieve this, the recipients measure the distributed quantum signature states using a new type of quantum measurement, quantum state elimination (e.g. Barnett 2009, Bandyopadhyay et al 2013). This significantly advances QDS as a quantum technology with potential for real applications.
    Physical Review Letters 11/2013; 113(4). DOI:10.1103/PhysRevLett.113.040502 · 7.73 Impact Factor
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    ABSTRACT: The design, modeling, fabrication, and characterization of single-photon avalanche diode detectors with an epitaxial Ge absorption region grown directly on Si are presented. At 100 K, a single-photon detection efficiency of 4% at 1310 nm wavelength was measured with a dark count rate of ~ 6 megacounts/s, resulting in the lowest reported noise-equivalent power for a Ge-on-Si single-photon avalanche diode detector (1×10-14 WHz-1/2). The first report of 1550 nm wavelength detection efficiency measurements with such a device is presented. A jitter of 300 ps was measured, and preliminary tests on after-pulsing showed only a small increase (a factor of 2) in the normalized dark count rate when the gating frequency was increased from 1 kHz to 1 MHz. These initial results suggest that optimized devices integrated on Si substrates could potentially provide performance comparable to or better than that of many commercially available discrete technologies.
    IEEE Transactions on Electron Devices 11/2013; 60(11):3807-3813. DOI:10.1109/TED.2013.2282712 · 2.36 Impact Factor
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    ABSTRACT: As society becomes more reliant on electronic communication and transactions, ensuring the security of these interactions becomes more important. Digital signatures are a widely used form of cryptography which allows parties to certify the origins of their communications, meaning that one party, a sender, can send information to other parties in such a way that messages cannot be forged. In addition, messages are transferrable, meaning that a recipient who accepts a message as genuine can be sure that if it is forwarded to another recipient, it will again be accepted as genuine. The classical digital signature schemes currently employed typically rely on computational complexity for security. Quantum digital signatures offer the potential for increased security. In our system, quantum signature states are passed through a network of polarization maintaining fiber interferometers (a multiport) to ensure that recipients will not disagree on the validity of a message. These signatures are encoded in the phase of photonic coherent states and the choice of photon number, signature length and number of possible phase states affects the level of security possible by this approach. We will give a brief introduction into quantum digital signatures and present results from our experimental demonstration system.
    Proceedings of SPIE - The International Society for Optical Engineering 10/2013; DOI:10.1117/12.2028720 · 0.20 Impact Factor
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    ABSTRACT: We have used an InGaAs/InP single-photon avalanche diode detector module in conjunction with a time-of-flight depth imager operating at a wavelength of 1550 nm, to acquire centimeter resolution depth images of low signature objects at stand-off distances of up to one kilometer. The scenes of interest were scanned by the transceiver system using pulsed laser illumination with an average optical power of less than 600 µW and per-pixel acquisition times of between 0.5 ms and 20 ms. The fiber-pigtailed InGaAs/InP detector was Peltier-cooled and operated at a temperature of 230 K. This detector was used in electrically gated mode with a single-photon detection efficiency of about 26% at a dark count rate of 16 kilocounts per second. The system's overall instrumental temporal response was 144 ps full width at half maximum. Measurements made in daylight on a number of target types at ranges of 325 m, 910 m, and 4.5 km are presented, along with an analysis of the depth resolution achieved.
    Optics Express 09/2013; 21(19):22098-22113. DOI:10.1364/OE.21.022098 · 3.53 Impact Factor
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    ABSTRACT: Intensity correlation measurements form the basis of many experiments based on spontaneous parametric down-conversion. In the most common situation, two single-photon avalanche diodes and coincidence electronics are used in the detection of the photon pairs, and the coincidence count distributions are measured by making use of some scanning procedure. Here we analyze the measurement of intensity correlations using multielement detector arrays. By considering the detector parameters such as the detection and noise probabilities, we found that the mean number of detected photons that maximizes the visibility of the two-photon correlations is approximately equal to the mean number of noise events in the detector array. We provide expressions predicting the strength of the measured intensity correlations as a function of the detector parameters and on the mean number of detected photons. We experimentally test our predictions by measuring far-field intensity correlations of spontaneous parametric down-conversion with an electron multiplying charge-coupled device camera, finding excellent agreement with the theoretical analysis.
    Physical Review A 07/2013; 88(1):013816. DOI:10.1103/PhysRevA.88.013816 · 2.99 Impact Factor
  • The European Conference on Lasers and Electro-Optics; 05/2013
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    ABSTRACT: This paper highlights a significant advance in time-of-flight depth imaging: by using a scanning transceiver which incorporated a free-running, low noise superconducting nanowire single-photon detector, we were able to obtain centimeter resolution depth images of low-signature objects in daylight at stand-off distances of the order of one kilometer at the relatively eye-safe wavelength of 1560 nm. The detector used had an efficiency of 18% at 1 kHz dark count rate, and the overall system jitter was ~100 ps. The depth images were acquired by illuminating the scene with an optical output power level of less than 250 µW average, and using per-pixel dwell times in the millisecond regime.
    Optics Express 04/2013; 21(7):8904-15. DOI:10.1364/OE.21.008904 · 3.53 Impact Factor
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    ABSTRACT: Direct monitoring of singlet oxygen (<sup>1</sup>O<sub>2</sub>) luminescence is a particularly challenging infrared photodetection problem. <sup>1</sup>O<sub>2</sub>, an excited state of the oxygen molecule, is a crucial intermediate in many biological processes. We employ a low noise superconducting nanowire single-photon detector to record <sup>1</sup>O<sub>2</sub> luminescence at 1270 nm wavelength from a model photosensitizer (Rose Bengal) in solution. Narrow band spectral filtering and chemical quenching is used to verify the <sup>1</sup>O<sub>2</sub> signal, and lifetime evolution with the addition of protein is studied. Furthermore, we demonstrate the detection of <sup>1</sup>O<sub>2</sub> luminescence through a single optical fiber, a marked advance for dose monitoring in clinical treatments such as photodynamic therapy.
    Optics Express 02/2013; 21(4):5005-5013. DOI:10.1364/OE.21.005005 · 3.53 Impact Factor
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    ABSTRACT: Ge-on-Si single-photon detectors are fabricated and characterized at 1310 and 1550 nm. 4 % single-photon detection efficiency is observed at 1310 nm demonstrating the lowest reported noise equivalent power for Ge-on-Si single-photon detectors (1×10-14 WHz-1/2).
    Group IV Photonics (GFP), 2013 IEEE 10th International Conference on; 01/2013

Publication Stats

2k Citations
268.07 Total Impact Points

Institutions

  • 1989–2015
    • Heriot-Watt University
      • • Institute of Photonics and Quantum Sciences (IPaQS)
      • • School of Engineering and Physical Sciences
      • • Department of Physics
      • • Department of Electrical, Electronic and Computer Engineering
      Edinburgh, Scotland, United Kingdom
  • 2000
    • Politecnico di Milano
      Milano, Lombardy, Italy
  • 1999
    • University of Glasgow
      • Division of Electronics and Electrical Engineering
      Glasgow, Scotland, United Kingdom