Texte remanié de: Th.--Informatique--Barcelone, 1989. Titre de soutenance : Un sistema informático para el análisis estadístico de datos textuales. / Bibliogr. p. 199-202.

The facility to capture the arrival of a single photon, is the fundamental limit to the detection of quantised electromagnetic radiation. An image sensor capable of capturing a picture with this ultimate optical and temporal precision is the pinnacle of photo-sensing. The creation of high spatial resolution, single photon sensitive, and time-resolved image sensors in complementary metal oxide semiconductor (CMOS) technology offers numerous benefits in a wide field of applications. These CMOS devices will be suitable to replace high sensitivity charge-coupled device (CCD) technology (electron-multiplied or electron bombarded) with significantly lower cost and comparable performance in low light or high speed scenarios. For example, with temporal resolution in the order of nano and picoseconds, detailed three-dimensional (3D) pictures can be formed by measuring the time of flight (TOF) of a light pulse. High frame rate imaging of single photons can yield new capabilities in super-resolution microscopy. Also, the imaging of quantum effects such as the entanglement of photons may be realised. The goal of this research project is the development of such an image sensor by exploiting single photon avalanche diodes (SPAD) in advanced imaging-specific 130nm front side illuminated (FSI) CMOS technology. SPADs have three key combined advantages over other imaging technologies: single photon sensitivity, picosecond temporal resolution and the facility to be integrated in standard CMOS technology. Analogue techniques are employed to create an efficient and compact imager that is scalable to mega-pixel arrays. A SPAD-based image sensor is described with 320 by 240 pixels at a pitch of 8μm and an optical efficiency or fill-factor of 26.8%. Each pixel comprises a SPAD with a hybrid analogue counting and memory circuit that makes novel use of a low-power charge transfer amplifier. Global shutter single photon counting images are captured. These exhibit photon shot noise limited statistics with unprecedented low input-referred noise at an equivalent of 0.06 electrons. The CMOS image sensor (CIS) trends of shrinking pixels, increasing array sizes, decreasing read noise, fast readout and oversampled image formation are projected towards the formation of binary single photon imagers or quanta image sensors (QIS). In a binary digital image capture mode, the image sensor offers a look-ahead to the properties and performance of future QISs with 20,000 binary frames per second readout with a bit error rate of 1.7 x 10-3. The bit density, or cumulative binary intensity, against exposure performance of this image sensor is in the shape of the famous Hurter and Driffield densitometry curves of photographic film. Oversampled time-gated binary image capture is demonstrated, capturing 3D TOF images with 3.8cm precision in a 60cm range.

Large area detectors for time correlated single photon counting (TCSPC) are nowadays being implemented in CMOS technology to benefit a large variety of applications including positron emission tomography (PET) and 3D laser ranging (LiDAR), exploiting the advanced timing and counting capabilities inside single chips. Single photon avalanche diodes (SPADs) and silicon photomultipliers (SiPMs) represent a great option to realise such detectors thanks to their exceptional timing resolution and the ability to be arranged into arrays. Recently, digital SiPMs (dSiPMs) have been introduced to improve the integration with CMOS technology overcoming limitations on the readout of analogue SiPMs and thus improving the photon resolution of the detector. This work presents a 14GSamples=s time-to-digital converter (TDC) to improve the throughput of dSiPM sensors commonly limited by the sampling rate of the timing/counting readout circuitry. The converter has been demonstrated on a test chip in 130nm CMOS imaging technology paired with a novel XOR-based 32 32 SPAD array single-channel detector. The overall achieved throughput equals 1GEvents=s demonstrated in a direct time-of-flight LiDAR experiment. By acquiring a number of photons significantly higher than one per laser pulse, this approach represents the first example in TCSPC of an input rate and conversion rate both higher than the excitation rate. The following part of the work presents a modelling analysis on how to match the achieved high sampling rate / throughput of the single-channel TDC to the performance of a SPAD array. The impact of a selection of dSiPM design parameters, such as photon detection efficiency, dead time and size of the SPAD cell, number of cells per single-channel, digital N-to-1 combining network and channel bandwidth, on the overall sensor throughput and the dynamic range has been characterised thanks to a computational Monte-Carlo simulator and useful equations describing each of the processes in the sensing chain. The pile-up effect, i.e. the event-loss causing non-linear distortions on the output signal, has been characterised on each element of the dSiPM and optimisations have been proposed. Event losses in the SPAD cells due to dead time, in the digital combining network due to network dead time and single-channel bandwidth have all been identified, simulated and described by analytical equations. All the results coming from the theoretical analysis have been reproduced in real dSiPM design thanks to a reconfigurable test chip realised in the same 130nm CMOS imaging technology specifically to validate the proposed theory. The manufactured test chip provides the very first direct comparison between OR-based and XOR-based single-channel dSiPM sensors highlighting the promising timing and counting performance of the newly introduced XOR-based dSiPM. Direct evidence of pile-up distortions and subsequent reduction through design optimisations are demonstrated. A recommended design flow for next generation dSiPMs is proposed at the end of the publication.

Vancouver Island, British Columbia, is at the northern extent of natural climate zones conducive for grape growing, making vineyards susceptible to any changing weather patterns and temperature extremes. Grapevine monitoring is an important aspect of the viticulture industry, and remote sensing technologies are a powerful aid in reporting vegetation information for better vineyard management practices. However, the understanding of vine spectral responses as viewed by optical sensors has to be developed further, and was undertaken in this study. Chlorophyll pigments drive photosynthesis, a biochemical process in plants, which contributes to physiological performance and productivity, making it an appropriate leaf characteristic for detailed examination. This study aimed to develop a thorough understanding of the relationship between (i) leaf-level spectral reflectance and transmittance properties and (ii) pigment concentrations, via ground-based sampling. This was achieved through the examination of two ground campaign tools, as well as current spectral data processing techniques and workflow methods. A spectrometer and SPAD chlorophyll meter collected nondestructive measurements during leaf senescence and grape harvest, and wet chemical extraction methods determined chlorophyll content (expressed in terms of unit leaf area and leaf fresh weight). Reflectance indices,first order derivative indices, and a continuum removal approach were used to generate eighteen reflectance-based attributes. This study performed a series of chlorophyll estimation models through iterative ordinary least square regression, followed by two methods of model validation. Performance metrics indicated strong models with high explanatory power; the continuum removed depth normalized total area metric was presented as the optimal nondestructive attribute for accurate chlorophyll estimation for leaf level field campaigns (R2 = 0.93). Chlorophyll expressed in units of fresh weight yielded more consistent models than in units of leaf area. The chlorophyll meter also presented compelling results (R2 ≥ 0.78), and both sensors were determined to be appropriate for field validation campaigns for this vineyard study. / Graduate

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.

LiDAR is a remote sensing technology that uses a laser to map the surrounding environment. With its many applications, for example in autonomous vehicles, LiDAR is a growing field within technology and research. The silicon photomultiplier (SiPM) is a solid state device commonly used in the receiving system of a LiDAR. However, ambient light from sun or other light sources is also seen by the photodetector which creates noise in the receiving system. The purpose of this work is to examine how the performance of a 1D LiDAR with a SiPM receiver can be predicted, given a certain level of ambient light, target reflectance and measuring distance. This was carried through by working with mathematical models and comparing the outcomes to lab measurements of a certain LiDAR model. The outcome showed that describing the performance of the particular LiDAR by a model based on incident photon rate was difficult mainly due to the unknown relation between how the voltage signal threshold in the receiving electric circuit for when the LiDAR stops the time measurement relates to the number of microcells activated in the SiPM during a time span. However, the results obtained suggest a threshold value of between around 20 and 60 microcells activated within a 1 ns time interval, but further tests are needed in order to confirm or reject this. Of the two other approaches tried, the signal voltage model gave reasonable results for the values tested but in a rather indirect way. The other approach, describing the connection between DC noise and AC RMS noise in the receiving system gave results deviating between 40% and 320% from the lab results, i.e. not so good match. / LiDAR är en fjärranalysteknik som använder laser för att kartlägga ett geografiskt område. Med flertalet användningsområden, bland annat inom industrin för självstyrande fordon, är LiDAR ett växande teknik- och forskningsområde. Kisel-fotomultiplikatorn är en halvledarapparat som ofta används i LiDAR-mottagarsystemet. Bakgrundsljus från omgivningen detekteras dock också av fotodetektorn vilket orsakar  brus i mottagarsystemet. Detta arbete syftar till att testa metoder för hur prestandan hos en 1D LiDAR med en kisel-fotomultiplikator i mottagaren kan estimeras, i en viss nivå av bakgrundsljus, med en viss målreflektans på ett visst mätavstånd. Detta utfördes genom att arbeta med matematiska modeller och jämföra dess resultat med resultat från laborativa tester på en viss LiDAR-modell. Det visade sig vara svårt att beskriva prestandan för denna LiDAR enligt en modell baserad på fotonflöde, huvudsakligen på grund av den okända kopplingen mellan tröskelnivån i termer av voltsignal i mottagarkretsen då tidmätningen stoppas och antalet aktiverade mikroceller i kisel-fotomultiplikatorn under ett visst tidsintervall. De resultat som erhölls visar dock på en träskelnivå någonstans mellan 20 och 60 mikroceller inom ett 1 ns tidsintervall, men ytterligare tester bör genomföras för att konfirmera eller förkasta detta. Av de övriga två angreppssätten prövade, gav modellen baserad på voltsignal rimliga resultat för värdena testade men på ett relativt indirekt sätt. Försök till beskrivning av sambandet mellan DC brus och AC RMS brus i mottagarsystemet gav resultat med mellan 40% och 320% avvikelse från de laborativa mätningarna, relativt dåligt alltså.

Single-photon avalanche diodes (SPADs) capable of single photon detection are promising optical sensors for use as receivers in optical wireless communication (OWC) systems. In SPAD-based receivers, the intersymbol interference (ISI) effect caused by dead time is an important drawback that limits performance. In this thesis, we propose two novel SPAD operation receivers to reduce the ISI effect in SPAD-based OWC. To validate the feasibility of these two modes, we design a free-running SPAD front-end circuit with post-layout transient simulation results. This SPAD circuit is improved by a novel mixed passive-active quench and reset front-end circuit that achieves a very short dead time. Based on the traditional free-running mode, we design the clock-driven mode and time-gated mode to reduce the ISI effect through time-controlled operating signals. In this work, we develop a new simulation system to assess the ISI effect in On-Off Keying (OOK) modulated communication and pulse position modulated (PPM) communication. To accurately evaluate these three modes, we build a OWC platform to test our proposed SPAD receiver manufactured by TSMC 65 nm process. The Test results demonstrate that the clock-driven mode and time-gated mode receivers can improve the bit error rate (BER) performance in low data rate communication and high data rate high optical power communication, respectively. Moreover, compared to the free-running mode, the two proposed time-controlled modes achieve higher data rate communication and better noise tolerance ability in SPAD-based OWC. / Thesis / Master of Applied Science (MASc) / Optical communication involves using light as a signal to transmit information, and it is currently a highly popular field of research. However, optical receivers used in this type of communication often require specific conditions, which can limit the overall performance of the communication system. To address this issue, we have developed an optical sensor tailored for optical communication. This sensor boasts exceptional sensitivity, allowing it to detect individual particles of light, thereby substantially reducing the demand for signal intensity in the optical communication system. Moreover, we have devised three operational circuits that enhance the sensor's responsiveness to signals under specific communication conditions. We have created a mathematical model to evaluate the proposed optical sensor and the designed circuits, and subsequently manufactured the optical sensor. Both the simulation results and the actual test outcomes unequivocally demonstrate that our proposed sensor has the potential to enhance the performance of optical communication systems.

Agricultural production is the main source of income and major employer in many countries in Africa, including Senegal. Commercial sweet corn (Zea mays L. ssp. saccharata) production in Senegal is increasing in response to global marketing opportunities and offers producers the ability to increase income and diversify the cropping base. Production of optimum sweet corn yield and quality depends on adequate nutrient supply, particularly, nitrogen (N). Current N recommendations are based on recommendations specific to corn for grain. This study aimed to identify tools to estimate sweet corn N status and determine the most appropriate fertilizer dosage for sweet corn. Non-destructive remote sensing tools and ion exchange resin membranes (IEMs) were used to evaluate the effect of fertilizer dose. No differences in ear yield or yield components, normalized difference vegetation index (NDVI) values, biomass, N uptake or leaf N concentration due to fertilizer dose were detected at Ndiol. However, significant relationships existed between NDVI values and yield, biomass, and N uptake at the V9 growth stage. Only yield was affected by fertilizer dose at Sangalkam, and no consistent relationships were found between chlorophyll meter readings and others measured parameters. Treatment differences due to fertilizer dose for available NH4+ at V9 (Ndiol), and NO3- at V5 (Sangalkam) were found, however further research is needed to fully evaluate the usefulness of IEMs to measure available soil N. Based on these studies, sweet corn fertilizer rates should likely be based on 75% of the dose applied to field corn, however more work is needed to confirm this finding. Pearl millet (Pennisetum glaucum (L) R. Br.) is the most widely grown staple crop in Senegal. Introduction of drought tolerant millet genotypes has helped mitigate the effect of increased water shortage in the region, but little is known about the nutritional composition of these genotypes. Our objective was to compare millet grain nutritional composition among and between putative drought tolerant and drought sensitive pearl millet lines under drought stress and well-watered conditions. One field experiment was conducted in 2014 at the National Center for Agronomic Research (CNRA) of Bambey, Senegal (16°30' and 16° 28' N; 15o44' and 15o42' W). The experiment utilized a split-plot design with four replications. Water regime was the main plot experimental factor while genotype, a total of 20 was the sub-plot. Pearl millet genotypes were divided into three contrasting groups based on drought tolerance for comparisons. Water stress did not affect 100-grain weight, test weight, protein, soluble protein, starch, sugars, amino acids or vitamin B2 content of grains among VPD-groups. Accumulation of these constituents of pearl millet grain appear to be genetically controlled and are probably not affected by late drought stress. However, differences were noted among genotypes as the sensitive VPD-group accumulated greater soluble protein, starch and soluble sugars (except sucrose) than the tolerant and medium VPD-groups. The tolerant VPD-group, however, accumulated greater protein and vitamin B2 content. Arginine, proline and serine content was greater in the sensitive VPD-group, while lysine, aspartic acid, and glutamic acid were greater in the tolerant VPD-group. Glycine, histidine, threonine, alanine, tyrosine, valine, methionine, leucine, isoleucine, and phenylalanine were relatively equal in tolerant and sensitive VPD-groups. Calcium and Na levels were affected by water stress in the sensitive VPD-group, but differently. Calcium content was greatest for the sensitive group under drought stress, while sodium was the lowest. Iron accumulation in sensitive VPD-group increased under water stress. Potassium decreased for all VPD-groups under stress, while across water regime, K levels in the drought-sensitive group were lower. Selection for drought appears to effect many of the nutritional constituents of pearl millet grain, however many of these differences appear to be directly related to parameters known to effect plant water relations. / Master of Science

The release of new cultivars and improvement in management practices is necessary to examine the time and nitrogen (N) rates to be applied to obtain high yields. Also there is little information about the effect of the N rate and stage (vegetative or reproductive) on the sensitivity of plants of rice to cold in the reproductive stage. For these reasons four experiments were installed two in field and two in a greenhouse with the objective of determining the effect of N rates and application timing on yield and on the susceptibility of rice plants to low temperature in the reproductive stage. The experiments were conducted in the 2006/2007 and 2007/2008 growing season at INIA Treinta y tres, Uruguay. The experimental design in greenhouse was completely randomized in a factorial experimental design (factor A: stages or rates of N application and B factor: treatment of temperature), with four replications. To study the effect of the time of application of N, The treatments were application of N (30 kg ha-1) in the stages V4, V5, V6, V7, V8, R0, R1 and control without N in topdress. To study the effect of rates were applied to the factor A 0, 23, 46 and 69 kg ha-1,in V4 stage and the same rates in R0 stage. For the factor B of the two experiments were carried out two treatments: with and without cold (cold with the plants were treated with 12.5°C for 7 hours in 4 nights when the collar of the flag leaf was at the same height as the collar of the leaf below). Treatments from the field experiments were the same for the factor A of the experiments in greenhouse later explained, in a randomized block design with four replications. In a greenhouse the spikelets sterility was not affected by the application of N in different stages or the rates applied when the plants were subjected to cold. The cold treatment caused a temporary effect on the SPAD index retarding panicle emergency and reducing the size of the panicle, but did not affect yield. In the rice grown in the area after three years of livestock the plants respond to low rates and times of application of N in yield and its components / A liberação de novas cultivares e a melhoria nas práticas de manejo fazem necessário estudar as épocas e doses de N a serem aplicadas para obter altas produtividades. Também existem poucas informações a respeito do efeito das aplicações de doses de nitrogênio (N) em diferentes estádios (vegetativos ou reprodutivos) sobre a sensibilidade das plantas de arroz quando submetidas ao frio na fase reprodutiva. Em vista disto, foram instalados quatro experimentos dois em campo e dois em casa de vegetação com o objetivo de determinar o efeito da época e a dose de aplicação de N sobre a produtividade e sobre a Susceptibilidade de plantas de arroz irrigado à temperatura baixa na fase reprodutiva. Os experimentos foram conduzidos no ano agrícola 2006/2007 e 2007/2008 na estação experimental do INIA Treinta y Três, Uruguai. O delineamento experimental utilizado em casa de vegetação foi o inteiramente casualizado em esquema bifatorial (fator A: estádios ou doses de aplicação de N e fator B: tratamento de temperatura), com quatro repetições. Para estudar o efeito da época de aplicação de N, os tratamentos do fator A foram aplicação de N (30 kg ha-1) nos estádios V4, V5, V6, V7, V8, R0, R1 e a testemunha sem N em cobertura. Para estudar o efeito de doses foram aplicados para o fator A 0, 23, 46 e 69 kg ha-1de N no estádio V4 e as mesmas doses no estádio R0 e uma testemunha sem N em cobertura nos dois estádios No fator B dos dois experimentos realizou-se dois tratamentos: com e sem frio (com frio as plantas foram submetidas com 12,5°C durante 7 horas em 4 noites seguidas quando o colar da folha bandeira ficou à mesma altura que o colar da folha anterior). O delineamento em campo foi de blocos ao acaso com quatro repetições. Os tratamentos foram de estádios ou doses de aplicação de N iguais aos dos experimentos em casa de vegetação Em casa de vegetação a esterilidade de espiguetas não é afetada pela aplicação de N em estádios diferentes, nem pelas doses aplicadas, em função dos tratamentos de frio a que as plantas foram submetidas. O tratamento de frio provoca um efeito temporário no índice SPAD atrasando a emergência de panículas e reduzindo o tamanho da panícula, mas não afeta a produtividade. Em campo o arroz cultivado em área após três anos de pecuária há baixa resposta às doses e épocas de aplicação de N em cobertura sobre a produtividade de grãos e seus componentes.

Les métaux nobles (Au, Ag, Pt, Ir, Pd et Ru) sont utilisés en salle blanche pour la réalisation de dispositifs électroniques ou peuvent être apportés par les équipements de fabrication (composants d’alliage par exemple). Il a été montré qu’ils pouvaient impacter fortement les dispositifs. Il est alors nécessaire de procéder au contrôle des équipements pour diagnostiquer au plus tôt une contamination. Or, il n’existe pas de technique industrielle pour leur suivi et ce à des niveaux d’au moins 5.109 at.cm-2 - recommandation ITRS. Il se pose la question de la pertinence de ces recommandations en fonction des types de dispositifs (SPAD notamment). Dans un premier temps, les travaux ont consisté à développer une technique physico-chimique pour l’analyse des métaux nobles sur silicium par VPD-DC-ICPMS. Enfin, leur dangerosité vis-à-vis des équipements et des dispositifs a été évaluée d’après leur comportement en température et le DCR généré sur SPAD. / Noble metals (Au, Ag, Pt, Ir, Pd and Ru) are used for the fabrication of microelectronics devices or can be brought by manufacturing tools (alloy components for example). It is well known that these impurities are detrimental to the efficiency of the devices. This implies a real and present need for control of their introduction in clean rooms to diagnose as soon as possible a contamination. Yet, there are no industrial technique for their follow-up at levels about 5.109 at.cm-2 - ITRS recommendations. The relevance of these recommendations according to the electronic device (SPAD in particular) could be questioned. At first, this study consisted in developing a physicochemical technique for the analysis of noble metals on Si wafers by VPD-DC-ICPMS. Then, their dangerousness towards tools and devices was established according to their behavior in temperature and the DCR generated on SPAD devices.