56 research outputs found

    Design of Multi Gb/s Monolithically Integrated Photodiodes and Multi-Stage Transimpedance Amplifiers in Thin-Film SOI CMOS Technology

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    The development of new integrated high-speed Si receivers is requested for short distance optical data link and emerging optical storage (OS) systems, notably for the Gb/s Ethernet standard [1] - [8] and Blue DVD (Blu-Ray, HDDVD) [3], [4], [9]. As requirements on bandwidth, gain, power consumption as well as low read-out noise and cost are quite severe, an optimal design strategy of a monolithically integrated solution, i.e. with on-chip photodetector and transimpedance amplifier (TIA), is required. In optical communication, however, non integrated detectors are usually employed [2] - [8] since the particular indirect energy band properties of Silicon make this semiconductor not very efficient for optical reception at 850nm wavelength. As Si is the most widely used and low cost semiconductor material in electronics and due to the availability of low-cost 850nm transmitters, there is yet a great interest and challenge to integrate such receivers. 1 to 10 Gb/s, high sensitivity and low complexity, low-cost silicon photodetectors for the monolithic integration of optical receivers for short distance applications at 850nm are really an issue as the Si absorption thickness required for high-speed (low transit time and low capacitance) favors thin-film technologies for which the responsivity is low. Some solutions exist but at the price of more costly and complex fabrication processes [10-16]. At the system level, owing to its low dark current (pA range) [17], low capacitor (10fF) for the photodetector [1] and possibility to integrate this detector with high-performance low-capacitance transistors, global thin-film SOI monolithically integrated photoreceivers have potentially higher gain and lower noise performances which in turn, as we will show here, can increase the C-sensitivity and alleviate this requirement on the photodetector itself. Furthermore only SOI photodiodes have so far achieved bandwidth compatible with the 10Gb/s specification and even higher data rate among the "easy to integrate" Si photodetectors [1], [15], [16] and [18]. In the blue and UV wavelengths, these diodes achieve a high responsivity [17] and then combine all the advantages of high speed, low dark current and finally high sensitivity [1]. This makes SOI receivers the best candidate for blue DVD applications and future optical storage generation. This also suggests that blue wavelength for multi Gb/s short reach optical communication could be used in a near future under the condition that the recent progresses in blue emitting sources make them available [17, 19]. We present here a top-down design methodology, fully validated by Eldo circuit simulations [20] and experimental measurements, which allows to predict and optimize, starting from the speed requirements and the technological parameters, the architecture and performances of the receiver. Our approach generalizes the one proposed in [21] to all inversion regimes. In addition our design strategy is based on the gm id methodology [22] and allows one to optimize the diode and the transimpedance in a simultaneous way. Thanks to this modeling and the low capacitance of thin-film integrated SOI photodiodes, we have optimized various monolithic optical front-end suitable for 1 to 10 Gb/s short distance communication or Blue DVD applications that show the potentials of 0.13μm Partially-Depleted (PD) SOI CMOS implementation in terms of gain, sensitivity, power consumption, area and noise. In section 2 (Optical Receivers Basics), the simple resistor system is first presented as well as its limitations. The transimpedance amplifier is then introduced and its basic theory and concepts such as transimpedance gain, bandwidth and stability are derived. Important parameters to compare transimpedance amplifiers are also discussed as well as architectures most often used in the high speed communication area. Then in section "Design of Multistage Transimpedance Amplifiers", we present our top-down methodology to design transimpedance amplifiers in the case where the voltage gain of the voltage amplifier used in the TIA is independent of the feedback resistor Rf. This is usually the case when the TIA bandwidth is not too close to the transistors frequency limit ft of a given technology and leads to a multi-stage approach. Our design procedure is then applied to the design of a 3 stages 1GHz bandwidth transimpedance amplifier in a 0.13 μm PD-SOI CMOS technology. Finally, in section "Single stage Transimpedance Amplifier Modeling", we present a top-down methodology to design transimpedance amplifiers when the voltage gain depends on Rf. This is the case for very high-speed singlestage transimpedance amplifiers. Our design procedure is then applied to the design of a single stage 10GHz bandwidth transimpedance amplifier in a 0.13 μm PD-SOI CMOS technology and to the design of a 1GHz bandwidth single stage TIA in a 0.5 μm FD-SOI CMOS technology

    대역폭 증대 기술을 이용한 전력 효율적 고속 송신 시스템 설계

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    학위논문(박사) -- 서울대학교대학원 : 공과대학 전기·정보공학부, 2022.2. 정덕균.The high-speed interconnect at the datacenter is being more crucial as 400 Gb Ethernet standards are developed. At the high data rate, channel loss re-quires bandwidth extension techniques for transmitters, even for short-reach channels. On the other hand, as the importance of east-to-west connection is rising, the data center architectures are switching to spine-leaf from traditional ones. In this trend, the number of short-reach optical interconnect is expected to be dominant. The vertical-cavity surface-emitting laser (VCSEL) is a com-monly used optical modulator for short-reach interconnect. However, since VCSEL has low bandwidth and nonlinearity, the optical transmitter also needs bandwidth-increasing techniques. Additionally, the power consumption of data centers reaches a point of concern to affect climate change. Therefore, this the-sis focuses on high-speed, power-efficient transmitters for data center applica-tions. Before the presenting circuit design, bandwidth extension techniques such as fractionally-spaced feed-forward equalizer (FFE), on-chip transmission line, inductive peaking, and T-coil are mathematically analyzed for their effec-tiveness. For the first chip, a power and area-efficient pulse-amplitude modulation 4 (PAM-4) transmitter using 3-tap FFE based on a slow-wave transmission line is presented. A passive delay line is adopted for generating an equalizer tap to overcome the high clocking power consumption. The transmission line achieves a high slow-wave factor of 15 with double floating metal shields around the differential coplanar waveguide. The transmitter includes 4:1 multi-plexers (MUXs) and a quadrature clock generator for high-speed data genera-tion in a quarter-rate system. The 4:1 MUX utilizes a 2-UI pulse generator, and the input configuration is determined by qualitative analysis. The chip is fabri-cated in 65 nm CMOS technology and occupies an area of 0.151 mm2. The proposed transmitter system exhibits an energy efficiency of 3.03 pJ/b at the data rate of 48 Gb/s with PAM-4 signaling. The second chip presents a power-efficient PAM-4 VCSEL transmitter using 3-tap FFE and negative-k T-coil. The phase interpolators (PIs) generate frac-tionally-spaced FFE tap and correct quadrature phase error. The PAM-4 com-bining 8:1 MUX is proposed rather than combining at output driver with double 4:1 MUXs to reduce serializing power consumption. T-coils at the internal and output node increase the bandwidth and remove inter-symbol interference (ISI). The negative-k T-coil at the output network increases the bandwidth 1.61 times than without T-coil. The VCSEL driver is placed on the high VSS domain for anode driving and power reduction. The chip is fabricated in 40 nm CMOS technology. The proposed VCSEL transmitter operates up to 48 Gb/s NRZ and 64 Gb/s PAM-4 with the power efficiency of 3.03 pJ/b and 2.09 pJ/b, respec-tively.400Gb 이더넷 표준이 개발됨에 따라 데이터 센터의 고속 상호 연결이 더욱 중요해지고 있다. 높은 데이터 속도에서의 채널 손실에 의해 단거리 채널의 경우에도 송신기에 대한 대역폭 확장 기술이 필요하다. 한편, 데이터 센터 내 동-서 연결의 중요성이 높아지면서 데이터 센터 아키텍처가 기존의 아키텍처에서 스파인-리프로 전환되고 있다. 이러한 추세에서 단거리 광학 인터커넥트의 수가 점차 우세해질 것으로 예상된다. 수직 캐비티 표면 방출 레이저(VCSEL)는 일반적으로 단거리 상호 연결을 위해 사용되는 광학 모듈레이터이다. VCSEL은 낮은 대역폭과 비선형성을 가지고 있기 때문에, 광 송신기도 대역폭 증가 기술을 필요로 한다. 또한, 데이터 센터의 전력 소비는 기후 변화에 영향을 미칠 수 있는 우려 지점에 도달했다. 따라서, 본 논문은 데이터 센터 응용을 위한 고속 전력 효율적인 송신기에 초점을 맞추고 있다. 회로 설계를 제시하기 전에, 부분 간격 피드-포워드 이퀄라이저 (FFE), 온칩 전송선로, 인덕터, T-코일과 같은 대역폭 확장 기술을 수학적으로 분석한다. 첫 번째 칩은 저속파 전송선로를 기반으로 한 3-탭 FFE를 사용하는 전력 및 면적 효율적인 펄스-진폭-변조 4(PAM-4) 송신기를 제시한다. 높은 클럭 전력 소비를 극복하기 위해 이퀄라이저 탭 생성을 위해 수동소자 지연 라인을 채택했다. 전송 라인은 차동 동일평면도파관 주위에 이중 플로팅 금속 차폐를 사용하여 15의 높은 전달속도 감쇠를 달성한다. 송신기에는 4:1 멀티플렉서(MUX)와 4-위상 클럭 생성기가 포함되어 있다. 4:1 MUX는 2-UI 펄스 발생기를 사용하며, 정성 분석에 의해 입력 구성이 결정된다. 이 칩은 65 nm CMOS 기술로 제작되었으며 0.151 mm2의 면적을 차지한다. 제안된 송신기 시스템은 PAM-4 신호와 함께 48 Gb/s의 데이터 속도에서 3.03 pJ/b의 에너지 효율을 보여준다. 두 번째 칩에서는 3-탭 FFE 및 역회전 T-코일을 사용하는 전력 효율적인 PAM-4 VCSEL 송신기를 제시한다. 위상 보간기(PI)는 부분 간격 FFE 탭을 생성하고 4-위상 클럭 오류를 수정하는 데 사용된다. 직렬화 전력 소비를 줄이기 위해 출력 드라이버에서 MSB와 LSB를 두 개의 4:1 MUX를 통해 결합하는 대신 8:1 MUX를 통해 PAM-4로 결합하는 회로가 제안된다. 내부 및 출력 노드에서 T-코일은 대역폭을 증가시키고 기호 간 간섭(ISI)을 제거한다. 출력 네트워크에서 역회전 T-코일은 T-코일이 없는 경우보다 대역폭을 1.61배 증가시킨다. VCSEL 드라이버는 양극 구동 및 전력 감소를 위해 높은 VSS 도메인에 배치된다. 이 칩은 40 nm CMOS 기술로 제작되었다. 제안된 VCSEL 송신기는 각각 3.03pJ/b와 2.09pJ/b의 전력 효율로 최대 48Gb/s NRZ와 64Gb/s PAM-4까지 작동한다.ABSTRACT I CONTENTS III LIST OF FIGURES V LIST OF TABLES IX CHAPTER 1 INTRODUCTION 1 1.1 MOTIVATION 1 1.2 THESIS ORGANIZATION 5 CHAPTER 2 BACKGROUND OF HIGH-SPEED INTERFACE 6 2.1 OVERVIEW 6 2.2 BASIS OF DATA CENTER ARCHITECTURE 9 2.3 SHORT-REACH INTERFACE STANDARDS 12 2.4 ANALYSES OF BANDWIDTH EXTENSION TECHNIQUES 16 2.4.1 FRACTIONALLY-SPACED FFE 16 2.4.2 TRANSMISSION LINE 21 2.4.3 INDUCTOR 24 2.4.4 T-COIL 33 CHAPTER 3 DESIGN OF 48 GB/S PAM-4 ELECTRICAL TRANSMITTER IN 65 NM CMOS 43 3.1 OVERVIEW 43 3.2 FFE BASED ON DOUBLE-SHIELDED COPLANAR WAVEGUIDE 46 3.2.1 BASIC CONCEPT 46 3.2.2 PROPOSED DOUBLE-SHIELDED COPLANAR WAVEGUIDE 47 3.3 DESIGN CONSIDERATION ON 4:1 MUX 50 3.4 PROPOSED PAM-4 ELECTRICAL TRANSMITTER 53 3.5 MEASUREMENT 57 CHAPTER 4 DESIGN OF 64 GB/S PAM-4 OPTICAL TRANSMITTER IN 40 NM CMOS 64 4.1 OVERVIEW 64 4.2 DESIGN CONSIDERATION OF OPTICAL TRANSMITTER 66 4.3 PROPOSED PAM-4 VCSEL TRANSMITTER 69 4.4 MEASUREMENT 82 CHAPTER 5 CONCLUSIONS 88 BIBLIOGRAPHY 90 초 록 101박

    On-Chip Integrated Functional Near Infra-Red Spectroscopy (fNIRS) Photoreceiver for Portable Brain Imaging

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    RÉSUMÉ L'imagerie cérébrale fonctionnelle utilisant la Spectroscopie Fonctionnelle Proche-Infrarouge (SFPI) propose un outil portatif et non invasif de surveillance de l'oxygénation du sang. SFPI est une technique de haute résolution temporelle non invasive, sûr, peu intrusive en temps réel et pour l'imagerie cérébrale à long terme. Il permet de détecter des signaux hémodynamiques à la fois rapides et neuronaux ou lents. Outre les avantages importants des systèmes SFPI, ils souffrent encore de quelques inconvénients, notamment d’une faible résolution spatiale, d’un bruit de niveau modérément élevé et d’une grande sensibilité au mouvement. Afin de surmonter les limites des systèmes actuellement disponibles de SFPI non-portables, dans cette thèse, nous en avons introduit une nouvelle de faible puissance, miniaturisée sur une puce photodétecteur frontal destinée à des systèmes de SFPI portables. Elle contient du silicium photodiode à avalanche (SiAPD), un amplificateur de transimpédance (TIA), et « Quench-Reset », circuits mis en oeuvre en utilisant les technologies CMOS standards pour fonctionner dans les deux modes : linéaire et Geiger. Ainsi, elle peut être appliquée pour les deux fNIRS : en onde continue (CW- SFPI) et pour des applications de comptage de photon unique. Plusieurs SiAPDs ont été mises en oeuvre dans de nouvelles structures et formes (rectangulaires, octogonales, double APDs, imbriquées, netted, quadratiques et hexadecagonal) en utilisant différentes techniques de prévention de la dégradation de bord prématurée. Les principales caractéristiques des SiAPDs sont validées et l'impact de chaque paramètre ainsi que les simulateurs de l'appareil (TCAD, COMSOL, etc) ont été étudiés sur la base de la simulation et de mesure des résultats. Proposées SiAPDs techniques d'exposition avec un gain de grande avalanche, tension faible ventilation et une grande efficacité de détection des photons dans plus de faibles taux de comptage sombres. Trois nouveaux produits à haut gain, bande passante (GBW) et à faible bruit TIA sont introduits basés sur le concept de gain distribué, d’amplificateur logarithmique et sur le rejet automatique du bruit pour être appliqué en mode de fonctionnement linéaire. Le TIA proposé offre une faible consommation, un gain de haute transimpédance, une bande passante ajustable et un très faible bruit d'entrée et de sortie. Le nouveau circuit mixte trempe-reset (MQC) et un MQC contrôlable (CMQC) frontaux offrent une faible puissance, une haute vitesse de comptage de photons avec un commandable de temps de hold-off et temps de réinitialiser. La première intégration sur puce de SiAPDs avec TIA et Photon circuit de comptage a été démontrée et montre une amélioration de l'efficacité de la photodétection, spécialement en ce qui concerne la sensibilité, la consommation d'énergie et le rapport signal sur bruit.----------ABSTRACT Optical brain imaging using functional near infra-red spectroscopy (fNIRS) offers a direct and noninvasive tool for monitoring of blood oxygenation. fNIRS is a noninvasive, safe, minimally intrusive, and high temporal-resolution technique for real-time and long-term brain imaging. It allows detecting both fast-neuronal and slow-hemodynamic signals. Besides the significant advantages of fNIRS systems, they still suffer from few drawbacks including low spatial- resolution, moderately high-level noise and high-sensitivity to movement. In order to overcome the limitations of currently available non-portable fNIRS systems, we have introduced a new low-power, miniaturized on-chip photodetector front-end intended for portable fNIRS systems. It includes silicon avalanche photodiode (SiAPD), Transimpedance amplifier (TIA), and Quench- Reset circuitry implemented using standard CMOS technologies to operate in both linear and Geiger modes. So it can be applied for both continuous-wave fNIRS (CW-fNIRS) and also single-photon counting applications. Several SiAPDs have been implemented in novel structures and shapes (Rectangular, Octagonal, Dual, Nested, Netted, Quadratic and Hexadecagonal) using different premature edge breakdown prevention techniques. The main characteristics of the SiAPDs are validated and the impact of each parameter and the device simulators (TCAD, COMSOL, etc.) have been studied based on the simulation and measurement results. Proposed techniques exhibit SiAPDs with high avalanche-gain (up to 119), low breakdown-voltage (around 12V) and high photon-detection efficiency (up to 72% in NIR region) in additional to a low dark- count rate (down to 30Hz at 1V excess bias voltage). Three new high gain-bandwidth product (GBW) and low-noise TIAs are introduced and implemented based on distributed-gain concept, logarithmic-amplification and automatic noise-rejection and have been applied in linear-mode of operation. The implemented TIAs offer a power-consumption around 0.4 mW, transimpedance gain of 169 dBΩ, and input-output current/voltage noises in fA/pV range accompanied with ability to tune the gain, bandwidth and power-consumption in a wide range. The implemented mixed quench-reset circuit (MQC) and controllable MQC (CMQC) front-ends offer a quenchtime of 10ns, a maximum power-consumption of 0.4 mW, with a controllable hold-off and resettimes. The on-chip integration of SiAPDs with TIA and photon-counting circuitries has been demonstrated showing improvement of the photodetection-efficiency, specially regarding to the sensitivity, power-consumption and signal-to-noise ratio (SNR) characteristics

    Design of High-Speed CMOS Interface Circuits for Optical Communications

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    학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 정덕균.The bandwidth requirement of wireline communications has increased ex-ponentially because of the ever-increasing demand for data centers and high-performance computing systems. However, it becomes difficult to satisfy the requirement with legacy electrical links which suffer from frequency-dependent losses due to skin effect, dielectric loss, channel reflections, and crosstalk, resulting in a severe bandwidth limitation. In order to overcome this challenge, it is necessary to introduce optical communication technology, which has been mainly used for long-reach communications, such as long-haul net-works and metropolitan area networks, to the medium- and short-reach com-munication systems. However, there still remain important issues to be resolved to facilitate the adoption of the optical technologies. The most critical challeng-es are the energy efficiency and the cost competitiveness as compared to the legacy copper-based electrical communications. One possible solution is silicon photonics that has long been investigated by a number of research groups. De-spite inherent incompatibility of silicon with the photonic world, silicon pho-tonics is promising and is the only solution that can leverage the mature CMOS technologies. In this thesis, we summarize the current status of silicon photonics and pro-vide the prospect of the optical interconnection. We also present key circuit techniques essential to the implementation of high-speed and low-power optical receivers. And then, we propose optical receiver architectures satisfying the aforementioned requirements with novel circuit techniques.CHAPTER 1 INTRODUCTION 1 1.1 MOTIVATION 1 1.2 THESIS ORGANIZATION 6 CHAPTER 2 BACKGROUND OF OPTICAL COMMUNICATION 7 2.1 OVERVIEW OF OPTICAL LINK 7 2.2 SILICON PHOTONICS 11 2.3 HYBRID INTEGRATION 22 2.4 SILICON-BASED PHOTODIODES 28 2.4.1 BASIC TERMINOLOGY 28 2.4.2 SILICON PD 29 2.4.3 GERMANIUM PD 32 2.4.4 INTEGRATION WITH WAVEGUIDE 33 CHAPTER 3 CIRCUIT TECHNIQUES FOR OPTICAL RECEIVER 35 3.1 BASIS OF TRANSIMPEDANCE AMPLIFIER 35 3.2 TOPOLOGY OF TIA 39 3.2.1 RESISTOR-BASED TIA 39 3.2.2 COMMON-GATE-BASED TIA 41 3.2.3 FEEDBACK-BASED TIA 44 3.2.4 INVERTER-BASED TIA 47 3.2.5 INTEGRATING RECEIVER 48 3.3 BANDWIDTH EXTENSION TECHNIQUES 49 3.3.1 INDUCTOR-BASED TECHNIQUE 49 3.3.2 EQUALIZATION 61 3.4 CLOCK AND DATA RECOVERY CIRCUITS 66 3.4.1 CDR BASIC 66 3.4.2 CDR EXAMPLES 68 CHAPTER 4 LOW-POWER OPTICAL RECEIVER FRONT-END 73 4.1 OVERVIEW 73 4.2 INVERTER-BASED TIA WITH RESISTIVE FEEDBACK 74 4.3 INVERTER-BASED TIA WITH RESISTIVE AND INDUCTIVE FEEDBACK 81 4.4 CIRCUIT IMPLEMENTATION 89 4.5 MEASUREMENT RESULTS 93 CHAPTER 5 BANDWIDTH- AND POWER-SCALABLE OPTICAL RECEIVER FRONT-END 96 5.1 OVERVIEW 96 5.2 BANDWIDTH AND POWER SCALABILITY 97 5.3 GM STABILIZATION 98 5.4 OVERALL BLOCK DIAGRAM OF RECEIVER 104 5.5 MEASUREMENT RESULTS 111 CHAPTER 6 CONCLUSION 118 BIBLIOGRAPHY 120 초 록 131Docto

    Etude et caractérisation d'un capteur en silicium amorphe hydrogéné déposé sur circuit intégré pour la détection de particules et de rayonnements

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    Next generation experiments at the European laboratory of particle physics (CERN) require particle detector alternatives to actual silicon detectors. This thesis presents a novel detector technology, which is based on the deposition of a hydrogenated amorphous silicon sensor on top of an integrated circuit. Performance and limitations of this technology have been assessed for the first time in this thesis in the context of particle detectors. Specific integrated circuits have been designed and the detector segmentation, the interface sensor â chip and the sensor leakage current have been studied in details. The signal induced by the track of an ionizing particle in the sensor has been characterized and results on the signal speed, amplitude and on the sensor resistance to radiation are presented. The results are promising regarding the use of this novel technology for radiation detection, though limitations have been shown for particle physics application

    A Flexible, Highly Integrated, Low Power pH Readout

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    Medical devices are widely employed in everyday life as wearable and implantable technologies make more and more technological breakthroughs. Implantable biosensors can be implanted into the human body for monitoring of relevant physiological parameters, such as pH value, glucose, lactate, CO2 [carbon dioxide], etc. For these applications the implantable unit needs a whole functional set of blocks such as micro- or nano-sensors, sensor signal processing and data generation units, wireless data transmitters etc., which require a well-designed implantable unit.Microelectronics technology with biosensors has caused more and more interest from both academic and industrial areas. With the advancement of microelectronics and microfabrication, it makes possible to fabricate a complete solution on an integrated chip with miniaturized size and low power consumption.This work presents a monolithic pH measurement system with power conditioning system for supply power derived from harvested energy. The proposed system includes a low-power, high linearity pH readout circuits with wide pH values (0-14) and a power conditioning unit based on low drop-out (LDO) voltage regulator. The readout circuit provides square-wave output with frequency being highly linear corresponding to the input pH values. To overcome the process variations, a simple calibration method is employed in the design which makes the output frequency stay constant over process, supply voltage and temperature variations. The prototype circuit is designed and fabricated in a standard 0.13-μm [micro-meter] CMOS process and shows good linearity to cover the entire pH value range from 0-14 while the voltage regulator provides a stable supply voltage for the system

    Miniaturized Optical Probes for Near Infrared Spectroscopy

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    RÉSUMÉ L’étude de la propagation de la lumière dans des milieux hautement diffus tels que les tissus biologiques (imagerie optique diffuse) est très attrayante, car elle offre la possibilité d’explorer de manière non invasive le milieu se trouvant profondément sous la surface, et de retrouver des informations sur l’absorption (liée à la composition chimique) et sur la diffusion (liée à la microstructure). Dans la gamme spectrale 600-1000 nm, également appelée gamme proche infrarouge (NIR en anglais), l'atténuation de la lumière par le tissu biologique (eau, lipides et hémoglobine) est relativement faible, ce qui permet une pénétration de plusieurs centimètres dans le tissu. En spectroscopie proche infrarouge (NIRS en anglais), de photons sont injectés dans les tissus et le signal émis portant des informations sur les constituants tissulaires est mesuré. La mesure de très faibles signaux dans la plage de longueurs d'ondes visibles et proche infrarouge avec une résolution temporelle de l'ordre de la picoseconde s'est révélée une technique efficace pour étudier des tissus biologiques en imagerie cérébrale fonctionnelle, en mammographie optique et en imagerie moléculaire, sans parler de l'imagerie de la durée de vie de fluorescence, la spectroscopie de corrélation de fluorescence, informations quantiques et bien d’autres. NIRS dans le domaine temporel (TD en anglais) utilise une source de lumière pulsée, généralement un laser fournissant des impulsions lumineuses d'une durée de quelques dizaines de picosecondes, ainsi qu'un appareil de détection avec une résolution temporelle inférieure à la nanoseconde. Le point essentiel de ces mesures est la nécessité d’augmenter la sensibilité pour de plus grandes profondeurs d’investigation, en particulier pour l’imagerie cérébrale fonctionnelle, où la peau, le crâne et le liquide céphalo-rachidien (LCR) masquent fortement le signal cérébral. À ce jour, l'adoption plus large de ces techniques optique non invasives de surveillance est surtout entravée par les composants traditionnels volumineux, coûteux, complexes et fragiles qui ont un impact significatif sur le coût et la dimension de l’ensemble du système. Notre objectif est de développer une sonde NIRS compacte et miniaturisée, qui peut être directement mise en contact avec l'échantillon testé pour obtenir une haute efficacité de détection des photons diffusés, sans avoir recours à des fibres et des lentilles encombrantes pour l'injection et la collection de la lumière. Le système proposé est composé de deux parties: i) une unité d’émission de lumière pulsée et ii) un module de détection à photon unique qui peut être activé et désactivé rapidement. L'unité d'émission de lumière utilisera une source laser pulsée à plus de 80 MHz avec une largeur d'impulsion de picoseconde.----------ABSTRACT The study of light propagation into highly diffusive media like biological tissues (Diffuse Optical Imaging) is highly appealing due to the possibility to explore the medium non-invasively, deep beneath the surface and to recover information both on absorption (related to chemical composition) and on scattering (related to microstructure). In the 600–1000 nm spectral range also known as near-infrared (NIR) range, light attenuation by the biological tissue constituents (i.e. water, lipid, and hemoglobin) is relatively low and allows for penetration through several centimeters of tissue. In near-infrared spectroscopy (NIRS), a light signal is injected into the tissues and the emitted signal carrying information on tissue constituents is measured. The measurement of very faint light signals in the visible and near-infrared wavelength range with picosecond timing resolution has proven to be an effective technique to study biological tissues in functional brain imaging, optical mammography and molecular imaging, not to mention fluorescence lifetime imaging, fluorescence correlation spectroscopy, quantum information and many others. Time Domain (TD) NIRS employs a pulsed light source, typically a laser providing light pulses with duration of a few tens of picoseconds, and a detection circuit with temporal resolution in the sub-nanosecond scale. The key point of these measurements is the need to increase the sensitivity to higher penetration depths of investigation, in particular for functional brain imaging, where skin, skull, and cerebrospinal fluid (CSF) heavily mask the brain signal. To date, the widespread adoption of the non-invasive optical monitoring techniques is mainly hampered by the traditional bulky, expensive, complex and fragile components which significantly impact the overall cost and dimension of the system. Our goal is the development of a miniaturized compact NIRS probe, that can be directly put in contact with the sample under test to obtain high diffused photon harvesting efficiency without the need for cumbersome optical fibers and lenses for light injection and collection. The proposed system is composed of two parts namely; i) pulsed light emission unit and ii) gated single-photon detection module. The light emission unit will employ a laser source pulsed at over 80MHz with picosecond pulse width generator embedded into the probe along with the light detection unit which comprises single-photon detectors integrated with other peripheral control circuitry. Short distance source and detector pairing, most preferably on a single chip has the potential to greatly expedites the traditional method of portable brain imaging

    Topical Workshop on Electronics for Particle Physics

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    The purpose of the workshop was to present results and original concepts for electronics research and development relevant to particle physics experiments as well as accelerator and beam instrumentation at future facilities; to review the status of electronics for the LHC experiments; to identify and encourage common efforts for the development of electronics; and to promote information exchange and collaboration in the relevant engineering and physics communities

    Capacitive micromachined ultrasound transducer (CMUT) design and fabrication for intracardiac echocardiography

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    The objective of this research is to develop capacitive micromachined ultrasonic transducer (CMUT) arrays with novel geometry for intracardiac echocardiography (ICE) imaging along with a novel reliable CMUT fabrication process to improve the system performance. We used custom CMOS electronics and monolithically integrated our CMUT arrays to CMOS chips. The arrays are designed for 9-Fr (<3mm) ICE catheters over a total area of about 2.6x11 mm2 at around 7MHz center frequency with ~80% fractional bandwidth in both 1-D and 2-D configurations. The 1-D array transducer includes 64 channels with beam-steering capabilities for cross sectional ICE imaging application at distance range of about 5-cm. The ICE image with 40dB dynamic range from 7 metal wires has been obtained. Several 2-D (sparse) arrays are designed based on signal-to-noise ratio (SNR) optimization capable of generating volumetric images. The CMUT-on-CMOS technique is used for arrays integration with our ASICs using vias for top and bottom electrode connections to the related electronics pads. A 60V pulse is optimized during transmit operation and 2MPa surface pressure has been achieved that is in agreement with our simulation results. We also developed an improved CMOS compatible low temperature sacrificial layer fabrication process for CMUTs. The process adds the fabrication step of silicon oxide evaporation which is followed by a lift-off step to define the membrane support area without a need for an extra mask. The parasitic capacitance is reduced about 15% and device long-term test demonstrates 72-hours stable output pressure showing no significant degradation on performance. We have also developed a new energy-based calculation method for CMUT performance evaluation that is valid during both small and large signal operation since well-known frequency and capacitance based coupling coefficients definitions are not valid for large signal and nonlinear operation regimes. The quantitative modeling results show that CMUTs do not need DC bias to achieve high efficiency large signal transduction: AC only signals at half the operation frequency with amplitudes beyond the collapse voltage can provide energy conversion ratio (ECR) above 0.9 with harmonic content below -25dB. The overall modeling approach is also qualitatively validated by experiments.Ph.D
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