Dissertations / Theses: 'Detectors photon'

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Najafi, Faraz. "Superconducting nanowire single-photon detectors : new detector architectures and integration with photonic chips." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/99836.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 153-161).
Superconducting nanowire single-photon detectors (SNSPDs) are a promising technology for long-distance optical communication and quantum information processing. Recent advances in single-photon generation, storage and detection technologies have spurred interest in integration of these components onto a single microchip, which would act as a low-power non-classical optical processor. In this thesis, I will present a method for the scalable integration of SNSPDs with photonic chips. I will show that, using a micron-scale flip-chip process, waveguide-coupled SNSPDs can be integrated onto a variety of material systems with high yield. This technology enabled the assembly of the first photonic chip with multiple adjacent SNSPDs with average system detection efficiencies beyond 10%. Using this prototype, we will show the first on-chip detection of non-classical light. I will further demonstrate optimizations to the detector design and fabrication processes. These optimizations increased the direct fabrication yield and improved the timing jitter to 24 ps for detectors with high internal efficiency. Furthermore, I will show a novel single-photon detector design that may have the potential to reach photodetection dead times below 1ns.
by Faraz Najafi.
Ph. D.

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Fitzpatrick, Catherine Rose. "Single-photon metrology with superconducting nanowire single-photon detectors." Thesis, Heriot-Watt University, 2013. http://hdl.handle.net/10399/2633.

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Single-photon sources and detectors underpin the development of quantum photonic technologies. This thesis presents research into single-photon devices with a focus on telecom wavelengths. A two-channel superconducting nanowire single-photon detector (SNSPD) system was constructed and characterised. It provides free-running single-photon detection at telecom wavelengths with low dark counts and timing jitter below 90 ps FWHM. The system detection e ciency at 1310 nm is 1 % with a 1 kHz dark count rate, which was competitive when the SNSPD was built in 2009. In this work, the low timing jitter of the SNSPD was bene cial to the development of a two-photon interference experiment. Experiments were carried out with single-photon sources based on self-assembled InAs/GaAs quantum dots in micropillar cavities. Preliminary measurements of the second-order correlation function gave g(²)(τ=0) = 0.12 ± 0.04 with above-band excitation and g(²)( τ = 0) = 0:07 ± 0:05 with near-resonant excitation. These values agree with recent papers reporting improved measurements with near-resonant excitation. Irreparable damage to the sample prevented further investigation. This thesis also presents the design, construction and characterisation of a highresolution single-photon spectrometer for telecom wavelengths. The instrument, a scanning Fabry-Perot interferometer, was optimised for the characterisation of quantum photonic sources. It has a spectral resolution of 550 MHz and a free spectral range of (119.0 ± 0.4) GHz.

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Natarajan, Chandra Mouli. "Superconducting nanowire single-photon detectors for advanced photon-counting applications." Thesis, Heriot-Watt University, 2011. http://hdl.handle.net/10399/2432.

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The ability to detect infrared photons is increasingly important in many elds of scienti c endeavour, including astronomy, the life sciences and quantum information science. Improvements in detector performance are urgently required. The Superconducting Nanowire Single-Photon Detector (SNSPD/SSPD) is an emerging single-photon detector technology o ering broadband sensitivity, negligible dark counts and picosecond timing resolution. SNSPDs have the potential to outperform conventional semiconductor-based photon-counting technologies, provided the di culties of low temperature operation can be overcome. This thesis describes how these important challenges have been addressed, enabling the SNSPDs to be used in new applications. A multichannel SNSPD system based on a closed-cycle refrigerator has been constructed and tested. E cient optical coupling has been achieved via carefully aligned optical bre. Fibre-coupled SNSPDs based on (i) NbN on MgO substrates and (ii) NbTiN on oxidised Si substrates have been studied. The latter give enhanced performance at telecom wavelengths, exploiting the re ection from the Si=SiO2 interface. Currently, the detector system houses four NbTiN SNSPDs with average detection e ciency >20% at 1310 nm wavelength. We have employed SNSPDs in the characterisation of quantum waveguide circuits, opening the pathway to operating this promising platform for optical quantum computing for the first time at telecom wavelengths.

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Tapan, Ilhan. "Avalanche photodiodes as proportional photon detectors." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389143.

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Zhu, Di S. M. Massachusetts Institute of Technology. "Superconducting nanowire single-photon detectors on aluminum nitride photonic integrated circuits." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/108974.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 85-91).
With recent advances in integrated single-photon sources and quantum memories, onchip integration of high-performance single-photon detectors becomes increasingly important. The superconducting nanowire single-photon detector (SNSPD) is the leading single-photon counting technology for quantum information processing. Among various waveguide materials, aluminum nitride (AlN) is a promising candidate because of its exceptionally wide bandgap, and intrinsic piezoelectric and electro-optic properties. In this Master's thesis, we developed a complete fabrication process for making high-performance niobium nitride SNSPDs on AlN, and demonstrated their integration with AlN photonic waveguides. The detectors fabricated on this new substrate material have demonstrated saturated detection efficiency from visible to near-IR, sub-60-ps timing jitter, and ~6 ns reset time. This work will contribute towards building a fully integrated quantum photonic processor.
by Di Zhu.
S.M.

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Mattsson, Claes. "Fabrication and Characterization of Photon Radiation Detectors." Licentiate thesis, Sundsvall : Department of Information Technology and Media ; Institutionen för informationsteknologi och medier, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-37.

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Gauthier, Graham A. "Angular effects in the STACEE photon detectors." Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=78366.

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The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground based gamma-ray telescope located in Albuquerque, NM. This thesis describes the development of an instrument, at McGill University, to study the angular response of the STACEE photon detectors to specific lighting conditions. The STACEE photon detectors consist of a photomultiplier tube (PMT) which is optically coupled to a Dielectric Totally Internally Reflecting Concentrator (DTIRC). A deeper understanding and parameterization of each constituent of the STACEE detector is integral to optimizing of the performance of the detector itself.

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Dauler, Eric A. (Eric Anthony) 1980. "Multi-element superconducting nanowire single photon detectors." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/46377.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 140-148).
Single-photon-detector arrays can provide unparalleled performance and detailed information in applications that require precise timing and single photon sensitivity. Such arrays have been demonstrated using a number of single-photon-detector technologies, but the high performance of superconducting nanowire single photon detectors (SNSPDs) and the unavoidable overhead of cryogenic cooling make SNSPDs particularly likely to be used in applications that require detectors with the highest performance available. These applications are also the most likely to benefit from and fully utilize the large amount of information and performance advantages provided by a single-photon-detector array.Although the performance advantages of individual superconducting nanowire single photon detectors (SNSPDs) have been investigated since their first demonstration in 2001, the advantages gained by building arrays of multiple SNSPDs may be even more unique among single photon detector technologies. First, the simplicity and nanoscale dimensions of these detectors make it possible to easily operate multiple elements and to closely space these elements such that the active area of an array is essentially identical to that of a single element. This ability to eliminate seam-loss between elements, as well as the performance advantages gained by using multiple smaller elements, makes the multi-element approach an attractive way to increase the general detector performance (detection efficiency and maximum counting rate) as well as to provide new capabilities (photon-number, spatial, and spectral resolution). Additionally, in contrast to semiconductor-based single-photon detectors, SNSPDs have a negligible probability of spontaneously emitting photons during the detection process, eliminating a potential source of crosstalk between array elements.
(cont.) However, the SNSPD can be susceptible to other forms of crosstalk, such as thermal or electromagnetic interactions between elements, so it was important to investigate the operation and limitations of multi-element SNSPDs. This thesis will introduce the concept of a multi-element SNSPD with a continuous active area and will investigate its performance advantages, its potential drawbacks and finally its application to intensity correlation measurements.This work is sponsored by the United States Air Force under Contract #FA8721-05-C-0002. Opinions, interpretations, recommendations and conclusions are those of the authors and are not necessarily endorsed by the United States Government.
by Eric Dauler.
Ph.D.

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Pizzone, Andrea. "Advanced photon counting applications with superconducting detectors." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8630/.

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Superconducting nanowire single photon detectors (SNSPDs) have emerged as mature detection technology that oﬀers superior performance relative to competing infrared photon counting technologies. SNSPDs have the potential to revolutionize a range of advanced infrared photon counting applications, from quantum information science to remote sensing. The scale up to large area SNSPD arrays or cameras consisting of hundreds or thousands of pixels is limited by efficient readout schemes. This thesis gives a full overview of current SNSPD technology, describing design, fabrication, testing and applications. Prototype 4-pixel SNSPD arrays (30 x 30 µm2 and 60 x 60 µm2) were fabricated, tested and time-division multiplexed via a power combiner. In addition, a photon-number resolved code-division multiplexed 4-pixel array was simulated. Finally, a 100 m calibration-free distributed fibre temperature testbed, based on Raman backscattered photons detected by a single pixel fibre-coupled SNSPD housed in a Gifford McMahon cryostat was experimentally demonstrated with a spatial resolution of approximately 83 cm. At present, it is the longest range distributed thermometer based on SNSPD sensing.

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Sidorova, Mariia. "Timing Jitter and Electron-Phonon Interaction in Superconducting Nanowire Single-Photon Detectors (SNSPDs)." Doctoral thesis, Humboldt-Universität zu Berlin, 2021. http://dx.doi.org/10.18452/22296.

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Die vorliegende Doktorarbeit beschäftigt sich mit der experimentellen Studie zweier miteinander verbundener Phänomene: Dem intrinsischen Timing-Jitter in einem supraleitendenden Nanodraht-Einzelphotonen-Detektor (SNSPD) und der Relaxation der Elektronenenergie in supraleitenden Filmen. Supraleitende Nanodrähte auf einem dielektrischen Substrat als mikroskopische Grundbausteine jeglicher SNSPDs stellen sowohl für theoretische als auch für experimentelle Studien komplexe Objekte dar. Die Komplexität ergibt sich aus der Tatsache, dass SNSPDs in der Praxis stark ungeordnete und ultradünne supraleitende Filme verwenden, die eine akustische Fehlanpassung zu dem zugrundeliegenden Substrat aufweisen und einen Nichtgleichgewichts-Zustand implizieren. Die Arbeit untersucht die Komplexität des am weitesten in der SNSPD Technologie verbreiteten Materials, Niobnitrid (NbN), indem verschiedene experimentelle Methoden angewandt werden. Als eine mögliche Anwendung der SNSPD-Technologie wird ein Prototyp eines dispersiven Raman-Spektrometers mit Einzelphotonen-Sensitivität demonstriert.
This Ph.D. thesis is based on the experimental study of two mutually interconnected phenomena: intrinsic timing jitter in superconducting nanowire single-photon detectors (SNSPDs) and relaxation of the electron energy in superconducting films. Microscopically, a building element of any SNSPD device, a superconducting nanowire on top of a dielectric substrate, represents a complex object for both experimental and theoretical studies. The complexity arises because, in practice, the SNSPD utilizes strongly disordered and ultrathin superconducting films, which acoustically mismatch with the underlying substrate, and implies a non-equilibrium state. This thesis addresses the complexity of the most conventional superconducting material used in SNSPD technology, niobium nitride (NbN), by applying several distinct experimental techniques. As an emerging application of the SNSPD technology, we demonstrate a prototype of the dispersive Raman spectrometer with single-photon sensitivity.

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Sunter, Kristen Ann. "Optical Modeling of Superconducting Nanowire Single Photon Detectors." Thesis, Harvard University, 2014. http://nrs.harvard.edu/urn-3:HUL.InstRepos:13106421.

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Superconducting nanowire single photon detectors (SNSPDs) can detect single photons or low levels of infrared light in applications that require high speed and low timing jitter, such as integrated circuit analysis. Most applications also require a high device detection efficiency (DDE), but the DDE of SNSPDs is limited by many factors. A good optical design with an integrated optical cavity and dielectric layers can increase the absorptance of 1550-nm light in the active area to over 90%. Therefore, optical modeling using the transfer matrix method was used to guide the design and fabrication of high-efficiency detectors with a measured DDE of over 70%. In addition, finite element analysis was used to simulate the effect of adding different types of optical antennas to SNSPD designs to increase their active area without compromising their speed, and the fabrication of antennas integrated with nanowires achieved sub-10 nm gaps between features. Thin films of niobium nitride, the starting material of the SNSPDs, were investigated using several techniques for thin film characterization, including x-ray diffraction, Auger electron spectroscopy and x-ray photoelectron spectroscopy. Optical setups based on reflectometry and transmittometry were built to determine the film thickness more accurately than deposition time for optical modeling and to provide feedback on the deposition conditions. The optical setups are able to provide reproducible and precise thickness measurements to within 0.1 nm.
Engineering and Applied Sciences

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Bellei, Francesco. "Superconducting nanowire single photon detectors for infrared communications." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/109008.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 113-120).
The ever-increasing data sharing demands of modern technologies forces scientists to adopt new methods that can surpass the approaching limits of classical physics. Quantum optical communications and information, based on single-photon detectors offer the most promising possibility to reach new levels of data rate and communication security. Superconducting nanowire single-photon detectors (SNSPDs) have already been used in the past to demonstrate new protocols of quantum key distribution and are currently the best single-photon detection technology to enable quantum optical communication. With the goal of creating a global quantum communication network, both optical fiber and free-space optical communication technologies have been explored. In addition, the scientific community started pursuing smaller and cheaper cryogenic solutions to enable the use of SNSPDs on a large scale. In this thesis, I describe the design and development of a cryogenic SNSPD receivers in free-space and optical-fiber configurations for 1550-nm-wavelength. The first configuration was created with the goal of enabling optical communication in the mid-IR. I present future steps to achieve this goal. The second configuration was designed to enable a compact and scalable integration of multiple SNSPD channels in the same system. Our approach has the potential of enabling SNSPD systems with more than 64 channels.
by Francesco Bellei.
Ph. D.

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Najafi, Faraz. "Timing performance of superconducting nanowire single-photon detectors." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/97816.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 83-89).
Superconducting nanowire single-photon detectors (SNSPDs) are becoming increasingly popular for applications in quantum information and long-distance communication. While the detection efficiency of SNSPDs has significantly improved over time, their timing performance has largely remained unchanged. Furthermore, the photodetection process in superconducting nanowires is still not fully understood and subject to ongoing research. In this thesis, I will present a systematic study of the timing performance of different types of nanowire single-photon detectors. I will analyze the photodetection delay histogram (also called instrument response function IRF) of these detectors as a function of bias current, nanowire width and wavelength. The study of the IRF yielded several unexpected results, among them a wavelength-dependent exponential tail of the IRF and a discrepancy between experimental photodetection delay results and the predicted value based on the electrothermal model. These results reveal some shortcomings of the basic models used for SNSPDs, and may include a signature of the initial process by which photons are detected in superconducting nanowires. I will conclude this thesis by presenting a brief introduction into vortices, which have recently become a popular starting point for photodetection models for SNSPDs. Building on prior work, I will show that a simple image method can be used to calculate the current flow in presence of a vortex, and discuss possible implications of recent vortex-based models for timing jitter.
by Faraz Najafi.
S.M.

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Kirkwood, Robert A. "Superconducting single photon detectors for quantum information processing." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8136/.

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Single photon detectors are a vital part of many emerging technologies which harness the quantum properties of light to benefit the fields of communication, computation and sensing. Superconducting nanowire single photon detectors (SNSPDs) offer high detection efficiency, low dark count rates, low timing jitter, and infrared sensitivity that are required by the most demanding single photon counting applications. This thesis presents SNSPDs fabricated and tested at the University of Glasgow that are integrated with optical structures which enable enhanced detection efficiency and integration with waveguide circuit technology. The monolithic integration of waveguide circuit components presents a route towards realisation of an optical quantum information processor that has the stability and scalability to perform the demanding tasks of quantum computation. A novel process is introduced for incorporating superconducting detectors with single mode gallium arsenide waveguides and quantum dot single photon sources. Together these elements would enable the generation of quantum states of light which could be manipulated and detected on a single chip. Detectors are patterned in NbTiN thin superconducting films on to suspended nanobeam waveguides with better than 50 nm alignment accuracy. Low temperature electrical and optical testing confirms the detectors’ single photon sensitivity under direct illumination as well as to waveguide coupled light. Measured detectors were found to have internal registering efficiencies of 6.8 ± 2.4%. Enhancing absorption of photons into thin superconducting films is vital to the creation of high efficiency superconducting single photon detectors. Fabricating an SNSPD on a dielectric mirror creates a partial cavity that can be tailored to enhance detection of light at specific wavelengths. Devices have been fabricated and tested in this thesis with enhanced detection efficiency at infrared and visible wavelengths for quantum cryptography, remote sensing and life science applications. Detectors fabricated in NbTiN on GaAs/AlGaAs Bragg mirrors exhibited a system detection efficiency of 1.5% at 1500 nm wavelength for the best device measured. SNSPDs were also fabricated in NbN on aperiodic dielectric mirrors with a range of different bandwidths. A peak system detection efficiency of 82.7% at 808 nm wavelength was recorded.

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Jerjen, Iwan. "Superconducting tunnel junctions as energy resolving single photon detectors /." Zürich : ETH, 2007. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17113.

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Lapington, Jonathan Stephen. "New techniques for imaging photon counting and particle detectors." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411261.

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O'Connor, John Alexander. "Nano-optical studies of superconducting nanowire single-photon detectors." Thesis, Heriot-Watt University, 2011. http://hdl.handle.net/10399/2515.

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uperconducting single-photon detectors based on superconducting nanowires offer broadband single-photon sensitivity, from visible to mid-infrared wavelengths. They have attracted particular attention due to their promising performance at telecommunications wavelengths. The additional benefits of superconducting nanowire single-photon detectors (SNSPDs) include low dark count rates (Hz) and low timing jitter (sub 100 ps). SNSPDs have been employed in practical photon-counting applications such as quantum key distribution (QKD), operation of quantum waveguide circuits and quantum emitter characterisation. Major challenges in the development of SNSPDs are the improvement of device uniformity and achieving efficient optical coupling. Nano-optical techniques such as confocal microscopy can be used to image localised areas of SNSPDs providing a direct measurement of the device uniformity. The work in this thesis describes both initial nano-optical testing at visible wavelengths in liquid helium and the construction of a fibre based miniature confocal microscope configuration operating at telecommunications wavelengths for use in a closed cycle refrigerator. In both cases localised areas of SNSPDs can be studied whilst maintaining efficient optical coupling. The miniature confocal microscope configuration has sub-nanometre position resolution over a 30 μm x 30 μm area by way of a piezoelectric X-Y scanner. A full width at half maximum (FWHM) optical resolution of 1305 nm at a wavelength of 1550 nm is achieved. SNSPDs based upon niobium nitride (NbN) nanowires fabricated on magnesium oxide (MgO) have been studied. The microscope system has allowed us to map the temporal response (timing jitter and output pulse timing delay) of constricted (non-uniform) SNSPDs. By fitting to a theoretical model, the variations in output pulse timing delay have been shown to be caused by variations in hotspot resistances across the device. This observation has provided insights into the underlying physics of SNSPDs and especially the origins of timing jitter in SNSPDs. This provides a pathway to exploitation of this effect in next-generation device designs for applications such as imaging.

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Yoo, Seung-jin. "Micromachined wavelength selective microbolometer sensors operating at room temperature /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004406.

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Sidorova, Mariia [Verfasser]. "Timing Jitter and Electron-Phonon Interaction in Superconducting Nanowire Single-Photon Detectors (SNSPDs) / Mariia Sidorova." Berlin : Humboldt-Universität zu Berlin, 2021. http://d-nb.info/1226153380/34.

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Piyankarage, Viraj Vishwakantha Jayaweera. "Uncooled Infrared Photon Detection Concepts and Devices." Digital Archive @ GSU, 2009. http://digitalarchive.gsu.edu/phy_astr_diss/30.

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This work describes infrared (IR) photon detector techniques based on novel semiconductor device concepts and detector designs. The aim of the investigation was to examine alternative IR detection concepts with a view to resolve some of the issues of existing IR detectors such as operating temperature and response range. Systems were fabricated to demonstrate the following IR detection concepts and determine detector parameters: (i) Near-infrared (NIR) detection based on dye-sensitization of nanostructured semiconductors, (ii) Displacement currents in semiconductor quantum dots (QDs) embedded dielectric media, (iii) Split-off band transitions in GaAs/AlGaAs heterojunction interfacial workfunction internal photoemission (HEIWIP) detectors. A far-infrared detector based on GaSb homojunction interfacial workfunction internal photoemission (HIWIP) structure is also discussed. Device concepts, detector structures, and experimental results discussed in the text are summarized below. Dye-sensitized (DS) detector structures consisting of n-TiO2/Dye/p-CuSCN heterostructures with several IR-sensitive dyes showed response peaks at 808, 812, 858, 866, 876, and 1056 nm at room temperature. The peak specific detectivity (D*) was 9.5E+10 Jones at 812 nm at room temperature. Radiation induced carrier generation alters the electronic polarizability of QDs provided the quenching of excitation is suppressed by separation of the QDs. A device constructed to illustrate this concept by embedding PbS QDs in paraffin wax showed a peak D* of 3E+8 Jones at ~540 nm at ambient temperature. A typical HEIWIP/HIWIP detector structures consist of single (or multiple) period(s) of doped emitter(s) and undoped barrier(s) which are sandwiched between two highly doped contact layers. A p-GaAs/AlGaAs HEIWIP structure showed enhanced absorption in NIR range due to heavy/light-hole band to split-off band transitions and leading to the development of GaAs based uncooled sensors for IR detection in the 2 5 μm wavelength range with a peak D* of 6.8E+5 Jones. A HIWIP detector based on p-GaSb/GaSb showed a free carrier response threshold wavelength at 97 µm (~3 THz)with a peak D* of 5.7E+11 Jones at 36 μm and 4.9 K. In this detector, a bolometric type response in the 97 - 200 µm (3-1.5 THz) range was also observed.

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Rafferty, Helen Marie. "Electronic transport properties of silicon-germanium single photon avalanche detectors." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/20373/.

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Single photon avalanche detectors (SPADs) have uses in a number of applications, including time-of-flight ranging, quantum key distribution and low-light sensing. Germanium has an absorption edge at the key communications wavelengths of 1.3-1.55um, and can be grown epitaxially on silicon, however, SiGe SPADs exhibit a number of performance limitations, including low detection efficiencies, high dark counts and afterpulsing. Unintentional doping may affect electronic performance, and band-to-band tunnelling at high operational voltages SPADs may lead to noise currents. Additionally, defects in the Si/Ge interface lead to trap states within the bandgap and contribute to afterpulsing. This work investigates a range of critical performance parameters in SiGe SPADs. The effect of intentional and unintentional doping in SPADs on electric fields, potential profiles and carrier transport in the device is investigated, and optimal dopant profiles for a SiGe SPAD discussed. The dependence of band-to-band tunnelling currents in Ge on bias voltage, Ge thickness and temperature is investigated, and these currents are compared to other sources of noise currents in SPADs. DFT calculations of misfit dislocation structures in Ge are undertaken, to establish electronic bandstructures and optimised geometries for these defects, and identify trap states in the bandgap, which may contribute to afterpulsing and dark counts in SPADs. A number of directions for continuing work are identified, to progress understanding of noise currents and afterpulsing in SPADs.

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Yang, Joel K. (Joel Kwang wei). "Superconducting nanowire single-photon detectors and sub-10-nm lithography." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/53307.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 155-169).
Superconducting nanowire single-photon detectors (SNSPDs) are useful in applications such as free-space optical communications to achieve high-speed data transfer across vast distances with minimum transmission power. In this and other applications, SNSPDs with high detection efficiencies are required. To this end, we designed and fabricated an integrated optical cavity and anti-reflection coating that enhanced the detection efficiency of SNSPDs by almost threefold to current record values of 57% at 1550 nm wavelength. We also improved our understanding of SNSPDs by modeling the electro-thermal response of the detector. This model showed that, beyond the initial formation of a photon-induced resistance across the nanowire, Joule heating results in the growth of the resistive segment. While simple, this model was useful in designing SNSPDs that reset more quickly, and also in explaining an undesirable behavior of the SNSPDs where the devices latch into a resistive state and fail to reset. Like many other devices, such as transistors, SNSPDs would benefit from device miniaturization: SNSPDs with narrower nanowires have higher detection efficiencies and increased sensitivity to low-energy photons. In this thesis, we investigated the resolution performance of electron-beam lithography (EBL) by first improving the contrast performance of hydrogen silsesquioxane (HSQ) negative-tone resist. The contrast of HSQ was improved by adding NaCl salt to an aqueous NaOH developer solution. With this improvement, we achieved a high-resolution electron-beam lithography process capable of patterning structures at 9-nm-pitch dimensions.
(cont.) The ability to pattern sub-10-nm structures is useful for fabricating future high-performance SNSPDs, nanoimprint lithography molds, prototypes of next generation transistors and storage media, and templates for controlling the self-assembly of block copolymers (BCPs). While this EBL process affords high-resolution, it is inherently a low-throughput process due to the serial nature of the pattern exposure. As a result, EBL is not cost effective in fabricating densely-patterned devices in large volumes. However, coin-bining this top-down EBL process with bottom-up BCP self-assembly techniques, we can simultaneously achieve high resolution without sacrificing throughput or pattern registration. We demonstrated that high-throughput fabrication of a hexagonally-ordered array of posts could be achieved by patterning only a sparse array of posts with EBL and using block copolymers to complete the missing structures.
by Joel K. Yang.
Ph.D.

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23

Dean, Sam Patrick 1956. "The use and design of geiger mode avalanche diodes to count photons." Thesis, The University of Arizona, 1988. http://hdl.handle.net/10150/276761.

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Astronomers need single photon detectors to detect very faint light sources from deep space. An avalanche photodiode in the geiger mode is especially suited for the detection of single photons. Three by three arrays of avalanche photodiodes were fabricated. Breakdown voltages of 200V were measured. Large reverse currents prevented operating the array in the geiger mode. An improved design which minimizes the reverse current is needed. A commercial avalanche photodiode especially made for the geiger mode was tested and compared to a general purpose avalanche photodiode. Using the general purpose avalanche in the geiger mode was found to be unacceptable because when exposed to a weak light source, 90% of the output pulses were dark current pulses. A computer interface circuit was designed to read the time and location where photons were absorbed by the array. The circuit performed its function qualitatively, but it had a false triggering problem.

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Fancey, Stuart James. "Single-photon avalanche diodes for time-resolved photoluminescence measurements in the near infra-red." Thesis, Heriot-Watt University, 1996. http://hdl.handle.net/10399/1309.

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Herder, Charles H. (Charles Henry) III. "Designing and implementing a readout strategy for superconducting single photon detectors." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/63024.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 109-112).
Introduction: Photon detection is an integral part of experimental physics, high-speed communication, as well as many other high-tech disciplines. In the realm of communication, unmanned spacecraft are travelling extreme distances, and ground stations need more and more sensitive and selective detectors to maintain a reasonable data rate.[10] In the realm of computing, some of the most promising new forms of quantum computing require consistent and efficient optical detection of single entangled photons.[27] Due to projects like these, demands are increasing for ever more efficient detectors with higher count rates. The Superconducting Nanowire Single-Photon Detector (SNSPD) is one of the most promising new technologies in this field, being capable of counting photons as faster than 100MHz and with efficiencies around 50%. Currently, the leading competition is from the geiger-mode avalanche photodiode, which is capable of ~20- 70% efficiency at a ~5MHz count rate depending on photon energy. In spite of these advantages, the SNSPD is still a brand-new technology and as a result they do not have the same support hardware support as other detectors. As such, SNSPD's are much more difficult to integrate into an existing an experiment. Because of this difficulty, SNSPD's have not been deployed extensively for research or industrial applications. The signal analysis chain that is connected to this detector is one of the key choke points. Each detector count produces a 0.1 mV, 10 nS wide pulse with a maximum count frequency on the order of 100MHz. Currently, this signal is processed outside of the cryostat with a series of RF amplifiers and a high-speed counter. This design works for detector prototyping, but poses a series of problems with actual design implementation. Most importantly, it prevents our design from being scalable. Even though we can fabricate thousands of detectors on a single wafer, it would be extremely difficult to place that many RF lines without crosstalk or other interference. The purpose of this thesis is to build a more robust and scalable readout technology for SNSPDs. First, we will develop intermediate technologies that improve upon current readout technology and will be necessary to develop the final goal. Ultimately, we plan to build circuitry on-chip that will first convert each detector's analog signal to a digital signal and then condense the data from each detector into an externally clocked, single-bit output indicating the presence or absence of a photon at any detector. This will allow simultaneous readout of a large number of detectors on a single wafer. Additionally, our cryogenic will decrease the noise observed by the detector, as the amplifier is no longer operating at room temperature. Finally, our readout will provide a simple hardware API to be interfaced to a computer or embedded processing unit. The catch to this development process is that the entire system must operate at 4.2K or below. As such, one must either use HEMT CMOS or Rapid Single-Flux- Quantum (RSFQ) logic. HEMT CMOS is better suited to analog amplification of the output signal, while RSFQ circuitry is better suited to the construction of the SNSPD interface and digital logic. RSFQ circuitry is better suited as an input stage because input amplification with CMOS is difficult, as one must operate in the linear regime of a HEMT. This requires on the order of 1 mA at 1.8 V minimum, which results in approximately 2 mW per stage. This is to be compared against RSFQ comparators which utilize approximately 0.5 mA at almost no voltage, resulting in muW of dissipation per stage. Given that we are hoping to produce a large number of SNSPD input stages, RSFQ is clearly a better choice. However, we only have a small number of output signals from the cryostat, so it is much more reasonable to use CMOS, as we can attain larger signal amplitudes.
by Charles Henry Herder III.
M.Eng.

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Kohani, Shahab. "3D Trench Detectors for Charged Particle Tracking and Photon Science Applications." Thesis, New York University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10928035.

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Silicon tracking detectors are frequently used in particle collider experiments, as they can provide excellent spatial precision with little material in order to cause minimal track disruption. Due to a progressive increase in collider luminosities, a common trend in these experiments is the need for higher levels of radiation damage resistance. One proposed class of designs for pixel trackers in high luminosity colliders is the Silicon 3D trench detector. The same design can be scaled up for photon science applications.

The work discussed in this dissertation was performed as part of a collaboration between BNL, NYU, CNM and SUNY Stony Brook. The central aim of the work presented here was to evaluate the manufactured 3D trench detector prototypes and study their behavior in detail by performing a series of experimental measurements and TCAD simulations.

An experiment to measure the detector response to an Americium radioactive source was designed and used to study the noise level and charge collection efficiency of detector prototypes. An experimental system which measured the detector response to an infrared laser with computer controlled precision positioning was developed. This system was used to obtain laser pulse response maps of detectors, which in turn were utilized to investigate the dependence of charge collection efficiency of detectors on position, collection time and bias voltage. The same mapping technique was also used to study the change in irradiated detector response.

Detector response was simulated using the Silvaco TCAD Suite. These simulations were used to study depletion in large photon detectors and charge collection in response to laser hits. Approximate simulations of radiation damage were also performed to investigate the behavior of irradiated detectors. Leakage current and capacitance simulations before and after irradiation were also performed and compared to the experimental measurements. While significant variations in detector response between different prototypes were observed during the experiments, simulation results are still capable of explaining the general properties of the detectors. The combination of the simulation and the experimental results provides an understanding of the signal generation process in these detectors.

One observed problem is the large bias currents due to manufacturing surface defects. A double-sided version of the trench detector is proposed to mitigate this problem. Electric fields, depletion region shape and formation, bias voltage and transient current response of these detectors are simulated and compared with those of the standard trench detectors. Computer simulations show that the double-sided detectors also have some performance advantages over the original designs including larger more uniform spatial charge collection efficiency and higher radiation damage resistance. These simulation results and the general insensitivity of the proposed detectors to surface defects make the double-sided detectors worthy of further study.

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Schmidt, Wolfgang-Gustav Ekkehart [Verfasser]. "Superconducting Nanowire Single-Photon Detectors for Quantum Photonic Integrated Circuits on GaAs / Wolfgang-Gustav Ekkehart Schmidt." Karlsruhe : KIT Scientific Publishing, 2020. http://d-nb.info/1213447836/34.

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Wehner, Justin. "Investigation of resonant-cavity-enhanced mercury cadmium telluride infrared detectors." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0148.

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[Truncated abstract] Infrared (IR) detectors have many applications, from homeland security and defense, to medical imaging, to environmental monitoring, to astronomy, etc. Increasingly, the wave- length dependence of the IR radiation is becoming important in many applications, not just the total intensity of infrared radiation. There are many types of infrared detectors that can be broadly categorized as either photon detectors (narrow band-gap materials or quantum structures that provide the necessary energy transitions to generate free car- riers) or thermal detectors. Photon detectors generally provide the highest sensitivity, however the small transition energy of the detector also means cooling is required to limit the noise due to intrinsic thermal generation. This thesis is concerned with the tech- nique of resonant-cavity-enhancement of detectors, which is the process of placing the detector within an optically resonant cavity. Resonant-cavity-enhanced detectors have many favourable properties including a reduced detector volume, which allows improved operating temperature, or an improved signal to noise ratio (or some balance between the two), along with a narrow spectral bandwidth. ... Responsivity of another sample annealed for 20 hours at 250C in a Hg atmosphere (ex-situ) also shows resonant performance, but indicates significant shunting due the mirror layers. There is good agreement with model data, and the peak responsivity due to the absorber layer is 9.5×103 V/W for a 100 'm ×100 'm photoconductor at 80K. An effective lifetime of 50.4 ns is extracted for this responsivity measurement. The responsivity was measured as a function of varying field, and sweepout was observed for bias fields greater than 50 V/cm. The effective lifetime extracted from this measurement was 224 ns, but is an over estimate. Photodiodes were also fabricated by annealing p-type Hg(1x)Cd(x)Te for 10 hours at 250C in vacuum and type converting in a CH4/H2 reactive ion etch plasma process to form the n-p junction. There is some degradation to the mirror structure due to the anneal in vacuum, but a clear region of high reflection is observed. Measurements of current-voltage characteristics at various temperatures show diode-like characteristics with a peak R0 of 10 G measured at 80K (corresponding to an R0A of approximately 104 cm2. There was significant signal from the mirror layers, however only negligible signal from the absorber layer, and no conclusive resonant peaks.

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Nguyen, Thuyen Huu Manh. "A photovoltaic detector technology based on plasma-induced p-to-n type conversion of long wavelength infrared HgCdTe." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0098.

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[Truncated abstract] HgCdTe is the leading semiconductor material for the fabrication of high performance infrared photon detectors, in particular, for detection of radiation beyond the near infrared. State-of-the-art infrared detection and imaging systems are currently based around high density focal plane arrays consisting of HgCdTe photodiodes as detector elements. Despite the high performance of HgCdTe infrared detectors, and the many benefits they can offer to industry and society, their utilisation remains limited due to the high cost of production. The chemical composition and narrow bandgap of the HgCdTe material used for infrared detection means that the material is inherently very susceptible to defect formation caused by the processing procedures required for device fabrication. Consequently, fabrication of HgCdTe photodiode arrays have traditionally been characterised by low yields and high costs for arrays that meet required operability specifications. In this thesis a new photodiode fabrication technology with the potential to improve device yields over traditional fabrication technologies is presented. This new fabrication technology is distinguished from others by the use of plasma-induced p-to-n type conversion of HgCdTe for junction formation. This allows great simplification of the fabrication process and avoids high temperature processing during and after junction formation, and keeps the junction protected from the atmosphere at all stages of fabrication. The development of the photodiode fabrication technology using plasma-induced junction formation has involved characterising the electrical transport properties of the type-converted layers, fabrication and characterisation of photodiodes, and photodiode dark current modelling

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Yau, Tony Tsz-Hong. "Angular distribution of '1'2C(#gamma#, NN) reactions." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309394.

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Beckett, Martin Gregory. "High resolution infrared imaging." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388828.

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Strasburg, Jana Dee. "Characterization of avalanche photodiode arrays for temporally resolved photon counting /." Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9710.

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Plackett, Richard William Robert. "Photon detectors for the Ring Imaging Cherenkov counters of the LHCb experiment." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438199.

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Hu, Xiaolong Ph D. Massachusetts Institute of Technology. "Efficient superconducting-nanowire single-photon detectors and their applications in quantum optics." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/63073.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2011.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 123-131).
Superconducting-nanowire single-photon detectors (SNSPDs) are an emerging technology for infrared photon counting and detection. Their advantages include good device efficiency, fast operating speed, low dark-count rate, low timing jitter, free running mode, and no afterpulsing. The challenges to be addressed prior to real applications are cryogenic operations, small active areas, and efficiency-speed tradeoffs. This thesis presents the effort to address these challenges. A fiber-coupled SNSPD system with a large-area detector in a closed-cycle cryocooler has been built, demonstrating 24% system detection efficiency with a darkcount rate of -1000 counts/sec. As a result, the SNSPD system becomes a convenient tool with a single-mode fiber as the input channel and an SMA cable as the output channel. This system has enabled high-quality polarization-entanglement distribution at the wavelength of 1.3 tm. The 99.2% visibility in Hong-Ou-Mandel (HOM) interference measured in this experiment is the highest HOM visibility that has ever been reported for waveguide-based photon-pair sources. After entanglement is distributed, a pair rate of 5.8 pairs/sec at a pump power of 25 iW and two-photon quantum interference visibility of 97.7% have been measured. On the other hand, increasing the active area of the detector does decrease its speed. To address the issue of efficiency-speed tradeoff, SNSPDs have been integrated with optical nano-antennae. A 9- im-by-9- tm detector with 47% device efficiency and 5-ns reset time has been demonstrated. In terms of active area, device efficiency and speed, this SNSPD has the record performance among single-element SNSPDs. Finally, waveguide-integrated SNSPDs have been proposed and designed. The device structure permits efficient coupling of photons into a short nanowire, and thus, efficient and fast SNSPDs. This structure is compatible with on-chip photonic technologies, including inverse-taper couplers and ring resonators, that have been developed in recent years.
by Xiaolong Hu.
Ph.D.

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35

Archer, Lucy Elizabeth. "Optical properties of ultra-thin niobium nitride films for single photon detectors." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/112044.

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Thesis: S.M., Massachusetts Institute of Technology, Department of Physics, 2017.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 75-78).
In this thesis I made a study of the properties of reactively sputtered ultra-thin films of niobium nitride (NbN) and niobium titanium nitride (NbTiN). Using Variable Angle Spectral Ellipsometry (VASE), I found that the optical properties of NbN films appear to have a critical thickness above which the optical parameters stabilize. I also found that the deposition process has better stability over time for thicker films than for thinner ones; that is, when films are deposited weeks apart, the thinner films show more variation in thickness and optical properties than do the thicker films. The data also suggest that the crystallinity of the substrate upon which the NbN is deposited has a significant effect on the optical parameters. The set of films deposited for the optical study was also tested against a universal scaling law for thin film superconductors, which seems to support the existence of the critical thickness, below which the properties change significantly and do not conform to the power law scaling that holds for thicker films. Finally, I explored recipes for depositing NbTiN with our sputtering system, in the hope of creating films that have better properties than NbN to be used in device manufacturing. I was able to create films with the same properties as our current NbN films with minimal optimization, and further work in this area should result in NbTiN films that are better than our NbN films.
by Lucy Elizabeth Archer.
S.M.

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36

Shannon, Michael Paul. "The dosimetry of a highly-collimated bremsstrahlung source in air." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/34819.

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The characterization and measurement of the spatial, temporal and energy emission of air-scattered photons, electrons and neutrons generated near 10 MV or greater accelerator-based bremsstrahlung photon sources is becoming important in many applications. The national and homeland security research community is interested in developing technologies which can detect illicit materials at substantial standoff distances in outdoor environments. These systems are referred to as "active" interrogation systems and are defined as inspection systems that take advantage of an externally applied "source" to perform traditional imaging of, or to stimulate characteristic emissions from, an inspected object. A key concern in the development of these systems is the ability to effectively predict the dose equivalents at long standoff distances from these sources in order to ascertain the operational radiation safety of said systems. Current computational radiation transport simulation tools have the ability to effectively model these systems; however, a paucity of experimental data exists in comparing the results of these simulations. A methodology to assess the radiation dose surrounding a high-energy bremsstrahlung-based accelerator system for national defense applications was developed. Fluence-to-dose conversion coefficients for the International Commission on Radiation Units and Measurements operational quantity ambient dose equivalent were calculated for photons and electrons up to 25 MeV utilizing the Los Alamos National Laboratory Monte Carlo N-Particle code, MCNP5 Version 1.51. Special consideration was given to the treatment of secondary charged particle equilibrium in all simulations. An extensive set of system simulations was performed to model a prototype high-energy bremsstrahlung-based accelerator system to obtain photon, electron and neutron fluence spectra. These fluence data were folded with the calculated ambient dose equivalent conversion coefficients as well as previously published effective dose conversion coefficients. A set of integral air-scatter measurements for accelerator-generated primary and secondary radiations (photon and neutron) were performed around the prototype system in order to provide a comparative data set from which to determine the total dose equivalent both in the beam (on-axis) and outside of the beam (off-axis).

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Kahl, Oliver [Verfasser], and M. [Akademischer Betreuer] Wegener. "Superconducting Single-Photon Detectors for Integrated Quantum Optics / Oliver Kahl. Betreuer: M. Wegener." Karlsruhe : KIT-Bibliothek, 2016. http://d-nb.info/1093559098/34.

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38

Kröninger, Kevin. "Techniques to distinguish between electron and photon induced events using segmented germanium detectors." kostenfrei, 2007. http://mediatum2.ub.tum.de/doc/618987/document.pdf.

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Smale, Nigel John. "Multi-anode photon-multiplier readout electronics for the LHCb ring imaging Cherenkov detectors." Thesis, University of Oxford, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.410667.

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Young, Ross Donaldson. "Measurements of B± meson production at LHCb and characterisation of hybrid photon detectors." Thesis, University of Edinburgh, 2012. http://hdl.handle.net/1842/6272.

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LHCb is an experiment designed to make precision measurements of Charge- Parity violation in the B meson system. We report a measurement of the B± crosssection and production asymmetry, using B± → J/u K± decays collected at the LHCb detector in 2010 and 2011. Using 27.6 pb-1 of pp collisions at a centre-of-mass energy 7 TeV, we obtain a B± cross-section of [41.6 ± 0.6 (stat.) ± 3.0 (sys.) ± 4.2 (lumi.)] μb in the rapidity region 2 to 4.5. Using 371.1 pb-1 of pp collisions at a centre-of-mass energy 7 TeV, we obtain a B± production asymmetry of [-2.09 ± 1.20 ± 0.8 (CP) ]% in the same rapidity region. The Ring Imaging Cherenkov system of LHCb uses Hybrid photon detectors (HPDs) for single photon detection. This thesis summarises the use of ion feedback measurements as indicators of HPD vacuum quality.

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41

Charaev, Ilya [Verfasser]. "Improving the Spectral Bandwidth of Superconducting Nanowire Single-Photon Detectors (SNSPDs) / Ilya Charaev." Karlsruhe : KIT Scientific Publishing, 2018. http://www.ksp.kit.edu.

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42

Abdalla, Munir. "Pixel Detectors and Electronics for High Energy Radiation Imaging." Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3206.

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43

Richardson, Justin Andrew. "Time resolved single photon imaging in nanometer scale CMOS technology." Thesis, University of Edinburgh, 2010. http://hdl.handle.net/1842/7588.

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Time resolved imaging is concerned with the measurement of photon arrival time. It has a wealth of emerging applications including biomedical uses such as fluorescence lifetime microscopy and positron emission tomography, as well as laser ranging and imaging in three dimensions. The impact of time resolved imaging on human life is significant: it can be used to identify cancerous cells in-vivo, how well new drugs may perform, or to guide a robot around a factory or hospital. Two essential building blocks of a time resolved imaging system are a photon detector capable of sensing single photons, and fast time resolvers that can measure the time of flight of light to picosecond resolution. In order to address these emerging applications, miniaturised, single-chip, integrated arrays of photon detectors and time resolvers must be developed with state of the art performance and low cost. The goal of this research is therefore the design, layout and verification of arrays of low noise Single Photon Avalanche Diodes (SPADs) together with high resolution Time-Digital Converters (TDCs) using an advanced silicon fabrication process. The research reported in this Thesis was carried out as part of the E.U. funded Megaframe FP6 Project. A 32x32 pixel, one million frames per second, time correlated imaging device has been designed, simulated and fabricated using a 130nm CMOS Imaging process from ST Microelectronics. The imager array has been implemented together with required support cells in order to transmit data off chip at high speed as well as providing a means of device control, test and calibration. The fabricated imaging device successfully demonstrates the research objectives. The Thesis presents details of design, simulation and characterisation results of the elements of the Megaframe device which were the author’s own work. Highlights of the results include the smallest and lowest noise SPAD devices yet published for this class of fabrication process and an imaging array capable of recording single photon arrivals every microsecond, with a minimum time resolution of fifty picoseconds and single bit linearity.

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ThÃ, George AndrÃ Pereira. "Teoria e implementaÃÃo de detectores de fÃtons isolados para comunicaÃÃes quÃnticas em redes Ãpticas." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2111.

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nÃo hÃ
Tecnologia da InformaÃÃo QuÃntica Ã uma Ãrea multidisciplinar nova que tem recebido muita atenÃÃo por ser promissora e devido a seu alto potencial em resolver problemas ainda nÃo solucionados. Dentro desta grande Ãrea, as ComunicaÃÃes QuÃnticas estÃo bastante desenvolvidas. Nesta sub-Ãrea, distribuiÃÃo QuÃntica de Chaves Ã o campo mais avanÃado. Ela permite que duas partes, chamadas Alice e Bob, compartilhem uma chave criptogrÃfica atravÃs de um canal seguro (seguranÃa garantida por leis da mecÃnica quÃntica). A maior parte dos Sistemas de DistribuiÃÃo QuÃntica de Chaves Ã executada em enlaces de fibras Ãpticas e, nestes sistemas, a mais importante parte Ã o Detector de FÃtons Isolados. Detector de FÃtons Isolados Ã um equipamento capaz de absorver um fÃton e gerar um sinal TTL. Assim, em um Detector de FÃtons Isolados ideal, cada fÃton que chega deve disparar um pulso TTL na saÃda. Dado que a energia de um fÃton isolado Ã muito baixa, um fotodiodo de avalanche Ã usado para realizar o processo absorÃÃo do fÃtongeraÃÃo de portador, uma vez que este fotodiodo, se corretamente polarizado, pode disparar uma avalanche de portadores detectÃvel. ApÃs a avalanche ter se iniciado, ela deve ser extinta para evitar qualquer dano ao fotodiodo, o que Ã feito por um circuito de extinÃÃo de avalanche. O fotodiodo de avalanche Ã o elemento mais importante de um Detector de FÃtons Isolados e sua caracterizaÃÃo requer muita atenÃÃo. Neste contexto, esta dissertaÃÃo lida com aspectos teÃricos e prÃticos de Detectores de FÃtons Isolados para ComunicaÃÃes QuÃnticas. Inicia com a teoria de fotodiodos de avalanche e circuitos de extinÃÃo (resultados numÃricos de circuitos de extinÃÃo tambÃm sÃo mostrados), e segue atÃ a caracterizaÃÃo de um Detector de FÃtons Isolados construÃdo em laboratÃrio e suas aplicaÃÃes em metrologia de dispositivos Ãpticos, bem como em resoluÃÃo de nÃmero de fÃtons.
Quantum Information Technology is a new multi-disciplinary area which has received a lot of attention due to its promises and its high potential in solving problems still unsolved. In this big area, Quantum Communication is too much developed. In this subarea, Quantum Key Distribution is the most advanced field. It permits two parties, named Alice and Bob, sharing a cryptography key through a secure channel (guaranteed by laws of quantum mechanics). The most of Quantum Key Distribution Systems run over optical fiber links and, in these systems, the most important part is the Single-Photon Detector. Single-Photon Detector is an equipment able to absorb a photon and generate a TTL pulse. Thus, in an ideal Single-Photon Detector, each photon incoming must trigger a TTL pulse at the output. Since the energy level of a single-photon is too much low, an avalanche photodiode is used to perform the photon absorption-carrier generation process, once this photodiode if correctly biased can trigger a detectable avalanche of carriers. After the avalanche has been started, it must be quenched in order to avoid any damage to the photodiode, which is made by an avalanche quenching circuit. The avalanche photodiode is the most important element of a Single-Photon Detector and its characterization requires much attention. In this context, this dissertation deals with theoretical and practical aspects of Single-Photon Detectors for Quantum Communication. It starts from the theory of avalanche photodiodes and quenching circuits (numerical results of quenching circuits are also shown) and follows until the characterization of a home-made Single-Photon Detector and its applications in Metrology of optical devices and in Photon-Number Resolution as well.

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Schmidt, Wolfgang-Gustav Ekkehart [Verfasser], and M. [Akademischer Betreuer] Siegel. "Superconducting Nanowire Single-Photon Detectors for Quantum Photonic Integrated Circuits on GaAs / Wolfgang-Gustav Ekkehart Schmidt ; Betreuer: M. Siegel." Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/119312672X/34.

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46

Somerville, Laura. "Performance of the LHCb RICH photon detectors and tagging systematics for CP violation studies." Thesis, University of Oxford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425910.

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47

Chuah, Joon Huang. "A multi-pixel CMOS photon detector for the scanning electron microscope." Thesis, University of Cambridge, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.608077.

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Daibes, Figueroa Said. "Discrete NaI(TI) crystal detector optimization for small animal SPECT molecular imaging." Diss., Columbia, Mo. : University of Missouri-Columbia, 2005. http://hdl.handle.net/10355/5821.

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Thesis (Ph.D.)--University of Missouri-Columbia, 2005.
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (November 15, 2006) Vita. Includes bibliographical references.

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Eriksson, Charlotte. "Optimization of Dual Energy data acquisition using CdTe-detectors with electronic spectrum splitting." Thesis, Linköpings universitet, Tekniska högskolan, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-94742.

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Dual energy imaging has made it possible to enhance contrast in medical images using images containing different energy information, by combining low and high energy images. Dual energy data can either be acquired using double exposures or splitting the energy spectrum into two images using one exposure. This thesis presents investigations of dual energy imaging using a detector solution developed by XCounter which provides dual energy images in a single exposure with a threshold separating low and high energy images. Phantom experiments with phantoms of aluminum and plexiglas were performed using weighted logarithmic subtraction and basis material decomposition to produce dual energy images. Methods were validated and images were evaluated in terms of signal difference in noise ratio to find the threshold and tube voltage combination for optimum energy spectrum separation. The methods were also tested on biological materials using bone, soft tissue and iodine solution as contrast enhancer, to investigate K-edge imaging. Optimal separation of plexiglas and aluminum were found at 70 kVp and the threshold parameter set within a range of 8 to 9, which corresponds to approximately 30 to 34 keV. For K-edge imaging, the optimum separation were found close to K-edge energy of iodine. The results found in the phantom study correlated with results from the biological material study.

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Mollén, Albert. "Investigation of Ageing effects and Image stability in Hybrid Photon Pixel detectors at the LHCb experiment CERN." Thesis, Linköping University, Department of Physics, Chemistry and Biology, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-54734.

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The world’s largest particle accelerator, Large Hadron Collider, located at CERN outside Geneva performed its first proton-proton collisions in November 2009. One of the four main experiments is LHCb, studying rare decays of hadrons containing the beauty quark. An essential part of the particle identification in LHCb is made by the two Ring Imaging Cherenkov detectors. These detectors use pixel Hybrid Photon Detectors for detection and imaging of Cherenkov rings. This paper reports on measurements carried out on the Hybrid Photon Detectors, including a discussion of the results. In particular, ageing effect and image stability are studied. A fraction of the photon detectors show a degradation in performance within these fields.

Världens största partikelaccelerator, LHC, belägen vid CERN utanför Genève utförde sina första proton-proton kollisioner i November 2009. Ett av de fyra huvudexperimenten är LHCb, som studerar sällsynta sönderfall av hadroner innehållande b kvarken. En viktig del av partikelidentifikationen i LHCb görs av de två RICH detektorerna. Dessa använder hybrida fotondetektorer för detektering och avbildning av Cherenkov ringar. Denna rapport handlar om mätningar utförda på dessa hybrida fotondetektorer, med en diskussion av resultaten. I synnerhet studeras åldringseffekter och bildstabilitet. En andel av fotondetektorerna visar en degradering i prestanda inom dessa områden.

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Dissertations / Theses on the topic 'Detectors photon'

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