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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Single-Photon Avalanche Diode theory, simulation, and high performance CMOS integration

Webster, Eric Alexander Garner January 2013 (has links)
This thesis explores Single-Photon Avalanche Diodes (SPADs), which are solid-state devices for photon timing and counting, and concentrates on SPADs integrated in nano-scale CMOS. The thesis focuses on: the search for new theory regarding Geiger-mode operation; proving the utility of calibrated Technology Computer- Aided Design (TCAD) tools for accurately simulating SPADs for the first time; the investigation of how manufacture influences device operation; and the integration of high performance SPADs into CMOS which rival discrete devices. The accepted theories of SPAD operation are revisited and it is discovered that previously neglected minority carriers have many significant roles such as determining: after-pulsing, Dark Count Rate (DCR), bipolar “SPAD latch-up,” nonequilibrium DCR, and “quenching”. The “quenching” process is revisited and it is concluded that it is the “probability time” of ≈100-200ps, and not the previously thought latching current that is important. SPADs are also found to have transient negative differential resistance. The new theories of SPADs are also supported by steady-state 1D, 2D and 3D TCAD simulations as well as novel transient simulations and videos. It is demonstrated as possible to simulate DCR, Photon Detection Efficiency (PDE), guard ring performance, breakdown voltage, breakdown voltage variation, “quenching,” and transient operation of SPADs with great accuracy. The manufacture of SPADs is studied focusing on the operation and optimisation of guard rings and it is found that ion implantation induced asymmetry from the tilt and rotation/twist is critical. Where symmetric, guard rings fail first along the <100> directions due to enhanced mobility. Process integration rules are outlined for obtaining high performance SPADs in CMOS while maintaining compatibility with transistors. The minimisation of tunnelling with lightly-doped junctions and the reduction of ion implantation induced defects by additional annealing are found essential for achieving low DCR. The thesis demonstrates that it is possible to realise high performance SPADs in CMOS through the innovation of a “Deep SPAD” which achieves record PDE of ≈72% at 560nm with >40% PDE from 410-760nm, combined with 18Hz DCR, <60ps FWHM timing resolution, and <4% after-pulsing which is demonstrated to have potential for significant further improvement. The findings suggest that CMOS SPAD-based micro-systems could outperform existing photon timing and counting solutions in the future.
2

Analyse du bruit lors de la génération de somme de fréquences dans les cristaux de niobate de lithium périodiquement polarisés (PPLN) et applications en régime de comptage de photons / Noise analysis in the sum frequency generation process in lithium niobate crystals periodically polarized (PPLN) and applications in regime of counting of photons

Baudoin, Romain 27 November 2014 (has links)
Le processus de somme de fréquences optiques est utilisé dans certaines applications pour convertir des signaux de longueurs d’onde infrarouges vers le domaine de longueurs d’onde visibles. Cela permet de bénéficier de technologies plus performantes notamment en terme de détection et de propagation. Les travaux menés dans cette thèse s’intéressent à l’étude de phénomènes optiques parasites générés par ce processus non linéaire dans des cristaux de niobate de lithium périodiquement polarisés (PPLN) pour des applications de conversion de fréquences en régime de comptage de photons. La première partie de ce manuscrit montre l’intérêt du processus de somme de fréquences optiques dans le contexte technologique de la détection infrarouge en régime de comptage de photons, via le concept de détection hybride. Les éléments théoriques et l’état de l’art associés à la détection hybride seront également présentés dans cette première partie. La deuxième partie traite d’une étude comparative entre différents cristaux de PPLN pour la détection hybride à 1550 nm. Pour cela, une analyse expérimentale détaillée des processus parasites est effectuée. Les résultats de cette étude sont utilisés pour des applications en astronomie et en microscopie. Enfin, la troisième partie traite d’une application de la somme de fréquences en interférométrie stellaire. Les résultats de caractérisation des cristaux de PPLN sont mis à contribution dans l’optimisation d’un instrument pour l’astronomie appelé interféromètre à somme de fréquences. Les résultats d’observation sur le site astronomique du Mont Wilson ainsi que les perspectives de cette instrument y sont présentés. / The sum frequency generation process is used in differents applications to convert signals from infrared wavelengths to the field of visible wavelength. This allows to benefit of more efficient technologies in terms of detection and propagation. This thesis describes the study of noise phenomena generated by this process in crystals of periodically poled lithium niobate (PPLN) for frequency up-conversion applications in photon counting regime. The first part of the manuscript shows the advantage of sum frequency generation process in the technological environment of the infrared detection on single photon counting regime, using the concept of hybrid detection. The theoretical elements and the state of the art associated with hybrid detection will also be presented in this first part. The second part deals with a comparative study between different PPLN for hybrid detection at 1550 nm. A detailed experimental analysis of the noise process is performed. The results of this study are used for applications in astronomy and microscopy. The third part deals with an application of the sum frequency in stellar interferometry. The results of PPLN’s characterization are involved in optimizing an instrument for astronomy called sum frequency interferometer. The results of observation on the astronomical site of Mount Wilson and the prospects of this instrument are presented.
3

Superconducting Nanostructures for Quantum Detection of Electromagnetic Radiation

Jafari Salim, Amir 06 September 2014 (has links)
In this thesis, superconducting nanostructures for quantum detection of electromagnetic radiation are studied. In this regard, electrodynamics of topological excitations in 1D superconducting nanowires and 2D superconducting nanostrips is investigated. Topological excitations in superconducting nanowires and nanostrips lead to crucial deviation from the bulk properties. In 1D superconductors, topological excitations are phase slippages of the order parameter in which the magnitude of the order parameter locally drops to zero and the phase jumps by integer multiple of 2\pi. We investigate the effect of high-frequency field on 1D superconducting nanowires and derive the complex conductivity. Our study reveals that the rate of the quantum phase slips (QPSs) is exponentially enhanced under high-frequency irradiation. Based on this finding, we propose an energy-resolving terahertz radiation detector using superconducting nanowires. In superconducting nanostrips, topological fluctuations are the magnetic vortices. The motion of magnetic vortices result in dissipative processes that limit the efficiency of devices using superconducting nanostrips. It will be shown that in a multi-layer structure, the potential barrier for vortices to penetrate inside the structure is elevated. This results in significant reduction in dissipative process. In superconducting nanowire single photon detectors (SNSPDs), vortex motion results in dark counts and reduction of the critical current which results in low efficiency in these detectors. Based on this finding, we show that a multi-layer SNSPD is capable of approaching characteristics of an ideal single photon detector in terms of the dark count and quantum efficiency. It is shown that in a multi-layer SNSPD the photon coupling efficiency is dramatically enhanced due to the increase in the optical path of the incident photon.

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