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High-speed silicon photonic electro-optic Kerr modulation

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Photonics Research 2024年第1期12卷 51-60页

作者： jONATHAN PELTIER WEIWEI ZHANG LEOPOLD VIROT CHRISTIAN LAFFORGUE LUCAS DENIEL DELPHINE MARRIS-MORINI GUY AUBIN FARAH AMAR DENH TRAN XINGZHAO YAN CALLUM G.LITTLEjOHNS CARLOS ALONSO-RAMOS KE LI david j.thomson GRAHAM REED LAURENT VIVIEN University Paris-Saclay CNRSCentre for Nanoscience and Nanotechnology(C2N)Palaiseau 91120France University Grenoble Alpes CEALETIGrenoble 38000France Optoelectronics Research Centre Zepler Institute for Photonics and NanoelectronicsFaculty of Engineering and Physical SciencesUniversity of SouthamptonSouthampton SO171BJUK

Silicon-based electro-optic modulators contribute to easing the integration of high-speed and low-power consumption circuits for classical optical communications and data *** the plasma dispersion modulation,an alternative solution in silicon is to exploit the DC Kerr effect,which generates an equivalent linear electro-optical effect enabled by applying a large DC electric *** some theoretical and experimental studies have shown its existence in silicon,limited contributions relative to plasma dispersion have been achieved in high-speed modulation so *** paper presents high-speed optical modulation based on the DC Kerr effect in silicon PIN *** contributions of both plasma dispersion and Kerr effects have been analyzed in different waveguide configurations,and we demonstrated that the Kerr induced modulation is dominant when a high external DC electric field is applied in PIN ***-speed optical modulation response is analyzed,and eye diagrams up to 80 Gbit/s in NRZ format are obtained under a *** of 30 *** work paves the way to exploit the Kerr effect to generate high-speed Pockels-like optical modulation.

关键词： waveguide dispersion effect

Post-fabrication phase trimming of Mach–Zehnder interferometers by laser annealing of germanium implanted waveguides

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Photonics Research 2017年第6期5卷 97-101页

作者： XIA CHEN MILAN M.MILOSEVIC david j.thomson ALI Z.KHOKHAR YOHANN FRANZ ANTOINE F.j.RUNGE SAKELLARIS MAILIS ANNA C.PEACOCK GRAHAM T.REED Optoelectronics Research Centre University of Southampton

We demonstrate a novel high-accuracy post-fabrication trimming technique to fine-tune the phase of integrated Mach–Zehnder interferometers, enabling permanent correction of typical fabrication-based phase errors. The effective index change of the optical mode is 0.19 in our measurement, which is approximately an order of magnitude improvement compared to previous work with similar excess optical loss. Our measurement results suggest that a phase accuracy of 0.078 rad was achievable with active feedback control.

关键词： Post-fabrication phase trimming of Mach Zehnder interferometers by laser annealing of germanium implanted waveguides MZI

All-silicon carrier accumulation modulator based on a lateral metal-oxide-semiconductor capacitor

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Photonics Research 2018年第5期6卷 373-379页

作者： KAPIL DEBNATH david j.thomson WEIWEI ZHANG ALI Z.KHOKHAR CALLUM LITTLEjOHNS jAMES BYERS LORENZO MASTRONARDI MUHAMMAD K.HUSAIN KOUTA IBUKURO FREOERIC Y.GARDES GRAHAM T,REED SHINICHI SAITO Optoelectronics Research Centre University of SouthamptonSouthampton S017 1B JUK Faculty of Physical Sciences and Engineering University of SouthamptonSouthampton SO17 1BJUK

In silicon photonics, the carrier depletion scheme has been the most commonly used mechanism for demonstrating high-speed electro-optic modulation. However, in terms of phase modulation efficiency, carrieraccumulation-based devices potentially offer almost an order of magnitude improvement over those based on carrier depletion. Previously reported accumulation modulator designs only considered vertical metal-oxidesemiconductor(MOS) capacitors, which imposes serious restrictions on the design flexibility and integratability with other photonic components. In this work, for the first time to our knowledge, we report experimental demonstration of an all-silicon accumulation phase modulator based on a lateral MOS capacitor. Using a Mach–Zehnder interferometer modulator with a 500-μm-long phase shifter, we demonstrate high-speed modulation up to 25 Gbit∕s with a modulation efficiency(V_πL_π) of 1.53 V·cm.

关键词： All-silicon carrier accumulation modulator based on a lateral metal-oxide-semiconductor capacitor MZI

Apodized silicon photonic grating couplers for mode-order conversion

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Photonics Research 2019年第11期7卷 1036-1041页

作者： IOSIF DEMIRTZIOGLOU COSIMO LACAVA ABDUL SHAKOOR ALI KHOKHAR YONGMIN jUNG david j.thomson PERIKLIS PETROPOULOS Optoelectronics Research Centre University of Southampton

An out-of-plane silicon grating coupler capable of mode-order conversion at the chip–fiber interface is designed and fabricated. Optimization of the structure is performed through finite-difference time-domain simulations,and the final device is characterized through far-field profile and transmission measurements. A coupling loss of 3.1 dB to a commercial two-mode fiber is measured for a single TE0→ LP11 mode conversion grating, which includes a conversion penalty of 1.3 dB. Far-field patterns of the excited LP11 mode profile are also reported.

关键词： Apodized silicon photonic grating couplers for mode-order conversion

Treatment and prevention of epilepsy in onchocerciasis-endemic areas is urgently needed

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Infectious Diseases of Poverty 2024年第1期13卷 85-89页

作者： Robert Colebunders joseph Nelson Siewe Fodjo Olivia Kamoen Luis-jorge Amaral Amber Hadermann Chiara Trevisan Mark j.Taylor julia Gauglitz Achim Hoerauf Yasuaki Sato Katja Polman Maria-Gloria Basanez Dan Bhwana thomson Lakwo Gasim Abd-Elfarag Sebastien D.Pion Global Health Institute University of AntwerpAntwerpBelgium Department of Neurology Heilig Hart ZiekenhuisLierBelgium Department of Public Health Institute of Tropical MedicineAntwerpBelgium Liverpool School of Tropical Medicine LiverpoolUK Department of Computer Science University of AntwerpAntwerpBelgium Institute of Medical Microbiology Immunology and ParasitologyUniversity Hospital BonnBonnGermany German Center for Infection Research(DZIF) Partner Site Bonn-CologneBonnGermany School of Global Humanities and Social Sciences Nagasaki UniversityNagasakiJapan MRC Centre for Global Infectious Disease Analysis and London Centre for Neglected TropicalDisease Research Department of Infectious Disease EpidemiologySchool of Public HealthImperial College LondonLondonUK National Institute for Medical Research TangaTanzania Vector Control Division Ministry of HealthKampalaUganda School of Public Health University of JubaJubaSouth Sudan Access for Humanity JubaSouth Sudan French National Research Institute for Sustainable Development MontpellierFrance

Background There is increasing epidemiological evidence supporting the association between onchocerciasis and seizures, reinforcing the concept of onchocerciasis-associated epilepsy (OAE). The aim of this paper is to provide an update on the new knowledge about OAE and to propose recommendations to the World Health Organization how to address this public health *** text During the 2nd International Workshop on OAE held on 19-21 September, 2023, in Antwerp, Belgium, participants recognised OAE as a substantial yet neglected public health problem, particularly in areas of sub-Saharan Africa where onchocerciasis remains hyperendemic. Evidence from prospective population-based studies suggest that strengthening onchocerciasis elimination efforts leads to a significant reduction of OAE incidence. There is a need to validate an OAE case definition to estimate the burden of disease and identify onchocerciasis-endemic areas requiring intensification of onchocerciasis elimination programmes and integration of epilepsy care. It is expected that raising awareness about OAE will boost the population uptake of ivermectin. The implementation of a community-based epilepsy treatment programme offering free anti-seizure medications (ASMs) has shown high effectiveness in reducing the frequency of seizures and improving the overall quality of life of people with *** To reduce OAE burden, enhanced collaboration between onchocerciasis and mental health programmes at community, national, and international levels is required. Urgent efforts are needed to ensure the uninterrupted provision of free ASMs in onchocerciasis-endemic areas. Furthermore, OAE should be included in the quantification of the onchocerciasis disease burden.

关键词： Onchocerciasis Morbidity Burden of disease Prevention Ivermectin Epilepsy Nodding syndrome Treatment Children Policy

Portable device to assess dynamic accuracy of global positioning system(GPS)receivers used in agricultural aircraft

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International journal of Agricultural and Biological Engineering 2014年第2期7卷 68-74页

作者： Steven j.thomson Yanbo Huang Lowrey A.Smith United States Department of Agriculture(USDA) Agricultural Research Service(ARS)Crop Production Systems Research UnitStonevilleMS 38776USA

A device was designed to test the dynamic accuracy of Global Positioning System(GPS)receivers used in agricultural aircraft and other aerial *** system works by directing a sun-reflected light beam from the ground to the aircraft using mirrors.A photo detector points downward from the aircraft to detect the light beam,and photo detection circuitry triggers an event in the guidance system data file at the aircraft’s location corresponding to the precisely georeferenced position on the *** details are presented on the mirror-based light reflection system and photo-electronic circuitry designed to trigger an event in the guidance system’s log *** example application evaluated the horizontal accuracy of a stand-alone GPS receiver by matching dynamic data with data from the aircraft’s guidance *** indicated a 2.16 s lead in position registered by the stand-alone receiver over that registered by the aircraft’s guidance system GPS receiver,which had been previously evaluated to be within 0.13 s of Real-Time Kinematic(RTK)-referenced time and position.

关键词： GPS receiver accuracy agricultural aircraft aerial application remote sensing georeferencing UAV

Characterization of spray deposition and drift from a low drift nozzle for aerial application at different application altitudes

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International journal of Agricultural and Biological Engineering 2011年第4期4卷 28-33页

作者： Yanbo Huang Steven j.thomson US Department of Agriculture Agricultural Research ServiceCrop Production Systems Research UnitStonevilleMS 38776USA

A complex interaction of controllable and uncontrollable factors is involved in aerial application of crop production and protection *** it is difficult to completely characterize spray deposition and drift,these important factors can be estimated with appropriate sampling protocol and *** height is an important variable influencing off-target spray drift,but this variable has not been easily measured or logged.A custom-configured aircraft-mounted laser with logging capabilities makes this *** study was designed to investigate droplet size and deposition characteristics of a low drift CP flat-fan nozzle at application altitudes 3.7 m,4.9 m,and 6.1 *** the study,CP flat-fan nozzles were set to a downward angle of 30 degrees applying a mixture of water,Syl-Tac®adjuvant,and Rubidium Chloride(RbCl)tracer at a 28.5 L/ha application *** droplets were collected using water sensitive paper(WSP)cards placed in the spray *** sheets were also placed in the swath and downwind for drift *** analysis indicated that median droplet diameter as determined by WSP in the spray swath was not significantly influenced by spray application ***,statistical analysis also indicated that concentration of RbCl tracer from Mylar samplers in the spray swath was not significantly influenced by application *** height had a significant effect on spray deposition from drift samplers,along with wind direction and relative *** results for drift samplers may have been influenced by shifts in wind direction that altered the relationship between orientation of samplers and wind.

关键词： deposition spray nozzle aerial application droplet spectra spray drift

Estimation of cotton yield with varied irrigation and nitrogen treatments using aerial multispectral imagery

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International journal of Agricultural and Biological Engineering 2013年第2期6卷 37-41页

作者： Yanbo Huang Ruixiu Sui Steven j.thomson Daniel K.Fisher Crop Production Systems Research Unit Agricultural Research ServiceUnited States Department of AgricultureStonevilleMS 38776USA

Cotton yield varies spatially within a *** variability can be caused by various production inputs such as soil properties,water management,and fertilizer *** multispectral imaging is capable of providing data and information to study effects of the inputs on yield qualitatively and quantitatively in a timely and cost-effective fashion.A 10-ha cotton field with irrigation and non-irrigation 2×2 blocks was used in this *** nitrogen application treatments were randomized with two replications within each *** plant canopy was closed,airborne multispectral images of the field were acquired using a 3-CCD MS4100 *** images were processed to generate various vegetation *** vegetation indices were evaluated for the best performance to characterize *** effect of irrigation on vegetation indices was *** for yield estimation were developed and verified by comparing the estimated and actual *** indicated that ratio of vegetation index(RVI)had a close relationship with yield(R^(2)=0.47).Better yield estimation could be obtained using a model with RVI and soil electrical conductivity(EC)measurements of the field as explanatory variables(R^(2)=0.53).This research demonstrates the capability of aerial multispectral remote sensing in estimating cotton yield variation and considering soil properties and nitrogen.

关键词： remote sensing multispectral imagery cotton yield nitrogen irrigation soil properties

Development and evaluation of low-altitude remote sensing systems for crop production management

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International journal of Agricultural and Biological Engineering 2016年第4期9卷 1-11页

作者： Yanbo Huang Steven j.thomson Howard j.Brand Krishna N.Reddy United States Department of Agriculture Agricultural Research ServiceCrop Production Systems Research UnitStoneville 38776USA United States Department of Agriculture National Institute of Food and AgricultureDivision of Agricultural SystemsWashington DC 20024USA Virginia Tech Department of Mechanical EngineeringBlacksburg 24061USA

Precision agriculture accounts for within-field variability for targeted treatment rather than uniform treatment of an entire *** is built on agricultural mechanization and state-of-the-art technologies of geographical information systems(GIS),global positioning systems(GPS)and remote sensing,and is used to monitor soil,crop growth,weed infestation,insects,diseases,and water status in farm fields to provide data and information to guide agricultural management *** agriculture began with mapping of crop fields at different scales to support agricultural planning and decision *** the development of variable-rate technology,precision agriculture focuses more on tactical actions in controlling variable-rate seeding,fertilizer and pesticide application,and irrigation in real-time or within the crop season instead of mapping a field in one crop season to make decisions for the next crop *** the development of aerial variable-rate systems,low-altitude airborne systems can provide high-resolution data for prescription variable-rate *** systems for multispectral imaging using a number of imaging sensors(cameras)were *** aerial vehicles(UAVs)provide a unique platform for remote sensing of crop fields at slow speeds and low-altitudes,and they are efficient and more flexible than manned agricultural airplanes,which often cannot provide images at both low altitude and low speed for capture of high-quality *** are also more universal in their applicability than agricultural aircraft since the latter are used only in specific *** study presents the low-altitude remote sensing systems developed for detection of crop stress caused by multiple ***,as a special platform,were discussed for crop sensing based on the researchers'studies.

关键词： low-altitude remote sensing agricultural airplane unmanned aerial vehicle(UAV) crop production management precision agriculture