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Conference on current developments in Lens design and optical engineering XVI

作者： Belay, Gebirie Y. Ottevaere, Heidi Vervaeke, Michael Van Erps, Jurgen Thienpont, Hugo Vrije Univ Brussel Fac Engn Dept Appl Phys & Photon TONA Brussels Photon TeamB PHOT B-1050 Brussels Belgium

ISBN: (纸本)9781628417449

Conventional multichannel imaging systems comprise of many optical channels having similar imaging properties, namely field-of-view (FOV) and angular resolution/magnification. We demonstrated that the different optical channels can be designed such that each optical channel captures a different FOV and angular resolution compared to its neighboring channels. We designed and experimentally demonstrated a three-channel multiresolution imaging system where the first optical channel has the narrowest FOV (7 degrees) and highest angular resolution (0.0096 degrees) and the third optical channel has the widest FOV (80 degrees) and lowest angular resolution (0.0780 degrees)(1). The second optical channel has intermediate properties. The performance of the demonstrated three-channel imaging system however was affected by chromatic aberrations as it was designed for a single wavelength of 587.6 nm. The first optical channel was largely influenced by longitudinal chromatic aberration while the third channel by lateral chromatic aberration. Therefore, we have replaced the aspherical refractive lenses by hybrid lenses, which contain diffractive structures on top of their refractive surfaces, in the three-channel multiresolution imaging system to reduce its chromatic aberrations. The performance of the three channels with hybrid lenses is compared with those of the corresponding channels without hybrid lenses. The longitudinal color aberration of the first optical channel has been reduced from 1.7 mm to 0.2 mm;whereas the lateral color aberration of the third optical channel has been reduced from 250 mu m to 14 mu m. In conclusion, the hybrid lenses have reduced the chromatic aberrations of the three channels and extended the operating spectral range of the imaging system in the visible wavelength range.

关键词： Multi-resolution imaging systems angular resolution multi-channel chromatic aberrations

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current density of carriers and emission rate in zinc selenide LED

Current density of carriers and emission rate in zinc seleni...

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International Conference on Electronic design (ICED)

作者： U.K. Sahbudin M.H.A. Wahid P. Poopalan N.A.M. Ahmad Hambali M.M. Shahimin S.N. Ariffin N.N.A. Saidi M.A.M. Azidin Semiconductor Photonics & Integrated Lightwave Systems (SPILS) School of Microelectronic Engineering Universiti Malaysia Perlis Perlis Malaysia Semiconductor Photonics & Integrated Lightwave Systems (SPILS) School of Microelectronic Engineering Universiti Malaysia Perlis Arau Perlis MY Faculty of Engineering National Defence University of Malaysia (UPNM) Kuala Lumpur

ISBN: (纸本)9781509021611

This work is based on the development of LED using a circular chip of ZnSe. Proper analyses of the proposed LED are performed by adding optical transition and nonradiative recombination processes. The voltage applied to the ZnSe LED ranges from 0 V to 3.5 V. The current-voltage characteristic and the flow of current density are obtained. At 2.5 V, the carriers move towards n-contact hence reduces the internal quantum efficiency. The carriers are observed to drift in opposite direction of the electric field until recorded voltage of 3.5 V where both carriers in line with the electric field. The emission at low voltage in p-layer is localized and caused the efficiency to reduce considerably.

关键词： Light emitting diodes Charge carrier processes ii-VI semiconductor materials Zinc compounds current density Radiative recombination

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Reconfigurable optical wireless applications in data centers

Reconfigurable optical wireless applications in data centers

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LEOS Summer Topical Meetings

作者： Mohsen Kavehrad Department of Electrical Engineering Center for Information & Communications Technology Research (CICTR) PA

ISBN: (纸本)9781509019014

Data centers (DCs) are a critical piece of today's networked applications in both private and public sectors. The key factors that have driven this trend are economies of scale, reduced management costs, better utilization of hardware via statistical multiplexing, and the ability to elastically scale applications in response to changing workload patterns. A robust datacenter network fabric is fundamental to the success of DCs and to ensure that the network does not become a bottleneck for high-performance applications. In this context, DC network design must satisfy several goals: high performance (e.g., high throughput and low latency), low equipment and management cost, robustness to dynamic traffic patterns, incremental expandability to add new servers or racks, and other practical concerns such as cabling complexity, and power and cooling costs. current DC network architectures do not seem to provide a satisfactory solution, with respect to the above requirements. In particular, traditional static (wired) networks are either: (i) overprovisioned to account for worst-case traffic patterns, and thus incur high cost (e.g., fat-trees or Clos), or (ii)oversubscribed (e.g., simple trees or leaf-spine architectures) which incur low cost but offer poor performance due to congested links. Recent works have tried to overcome the above limitations by augmenting a static (wired) “core” with some flexible links (RF-wireless or optical). These augmented architectures show promise, but offer only incremental improvement in performance. Specifically, RF-wireless based augmented solutions also offer only limited performance improvement, due to inherent interference and range constraints of RF links. optical solutions offer high-bandwidth links and low latency, but have limited scalability, offer only limited flexibility (e.g., bipartitematchings between the racks), and have a single point of failure. Furthermore, all the above architectures incur high cabling cost and complexity

关键词： Traffic control Complexity theory Robustness Cooling optical fiber networks Network topology

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Performance estimation of N-channel ZnO based thin film transistor using simulation

Performance estimation of N-channel ZnO based thin film tran...

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IEEE International Conference on Research in Computational Intelligence and Communication Networks (ICRCICN)

作者： Shashi Kant Dargar J K Srivastava Santosh Bharti Abha Nyati Department of Electronics and Communication Engineering Sir Padampat Singhania University Udaipur India

ISBN: (纸本)9781509010486

High optical transparency and low cost with excellent switching performance drew the attention of researchers in using ZnO as a potential material for TFT device design. The electrical parameter extraction of ZnO channel thin film transistor using simulation is carried out in Sentaurus TCAD tool. The scope of the research is to analyze the performance of the device on the basis of parameters extracted from its transfer characteristic. The device has shown high field effect mobility of order ~1 × 10 -4 , and significant on current -6.22 × 10 -6 A, off current ~ 1.26 × 10 -10 A with improved on-off ratio ~10 5 , which makes the device reliable for the next generation of flexible electronics and display devices.

关键词： Thin film transistors Zinc oxide ii-VI semiconductor materials Logic gates Integrated circuit modeling Threshold voltage Semiconductor device measurement

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Proceedings of SPIE - The International Society for optical engineering

Proceedings of SPIE - The International Society for Optical ...

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Conference on current developments in Lens design and optical engineering XVI

ISBN: (纸本)9781628417449

The proceedings contain 24 papers. The topics discussed include: integration design of endoscope with different viewing angles;ultra-compact hourglass lens for integrated cameras;testing and alignment of freeform based multi-mirror telescopes;tolerancing an optical freeform surface: an optical fabricator's perspective;manufacture and analysis of a refractive surface with variable asphericity to model the human cornea;modeling and design of a multichannel chromatic aberration compensated imaging system;temperature-dependent refractive index measurements of L-BBH2 glass for the Subaru CHARIS integral field spectrograph;cryogenic refractive indices of S-LAH55, S-LAH55V, S-LAH59, S-LAM3, S-NBM51, S-NPH2, S-PHM52, and S-TIH14 glasses;temperature-dependent refractive index measurements of CaF2, Suprasil 3001, and S-FTM16 for the Euclid near-infrared spectrometer and photometer;design considerations for an unconventional infrared prism with a 90 degree ray deviation;and high-performance LED luminaire for sports hall.

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Proceedings of SPIE - The International Society for optical engineering

Proceedings of SPIE - The International Society for Optical ...

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Sensors, Systems, and Next-Generation Satellites XIX

ISBN: (纸本)9781628418491

The proceedings contain 61 papers. The topics discussed include: overview of Japanese earth observation programs;on-orbit performance of the compact infrared camera (CIRC) onboard ALOS-2;current status of the dual-frequency precipitation radar on the global precipitation measurement core spacecraft;EarthCARE/CPR design results and PFM development status;development and pre-launch test status of second generation global imager (SGLI);concept study of a vegetation LIDAR on International Space Station;sensitivity study of SMILES-2 for chemical species;measurement of stratospheric and mesospheric winds with a submillimeter wave limb sounder: results from JEM/SMILES and simulation study for SMILES-2;visible and infrared detector developments supported by the European Space Agency;and low dark current MCT-based focal plane detector arrays for the LWIR and VLWIR developed at AIM.

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Proceedings of SPIE - The International Society for optical engineering

Proceedings of SPIE - The International Society for Optical ...

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Material Technologies and Applications to Optics, Structures, Components, and Sub-Systems ii

ISBN: (纸本)9781628417401

The proceedings contain 21 papers. The topics discussed include: design and manufacturing considerations for 0.25-1.5 meter beryllium telescopes for current and future space missions;new decade of shaped beryllium blanks;design and manufacturing considerations for high-performance gimbals used for land, sea, air, and space;application and testing of additive manufacturing for mirrors and precision structures;structured surfaces on metal optics;advanced thermal control for spacecraft applications;low-stress silicon cladding made by pulsed-ion-assisted evaporation;trade study of all-SiC lightweight primary mirror and metering structures for spaceborne telescope;recent development of fabrication of extreme light-weighted ceramic mirrors;and extreme stable and complex structures for opto-mechanical applications.

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Direct band gap In_xGa_1-xAs/Ge type ii strained quantum wells for short-wave infrared p-i-n photodetector

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optical MATERIALS 2015年 46卷 472-480页

作者： Harbi, N. Sfina, N. Jbeli, A. Lazzari, J-L Said, M. Fac Sci Monastir Dept Phys LMCN Monastir 5019 Tunisia Aix Marseille Univ UMR CNRS 7325 Ctr Interdisciplinaire Nanosci Marseille CINaM F-13288 Marseille 9 France King Khalid Univ Fac Sci & Art Mahail Assir Saudi Arabia Majmaah Univ Coll Sci & Humanities Ghat Ghat 11914 Saudi Arabia

We theoretically investigate GaAs/Ge/InGaAs as a quantum wells for the design of short-wave infrared p-i-n photodetectors in which the quantum well Ge/InGaAs is the active region. At room temperature, strained Ge/InxGa1-xAs becomes a direct band gap when In composition x is lower than 2.5% and 5% respectively. We have calculated the electronic band parameiers for the heterointerface Ge/InxGa1-xAs. Then, a type-ii strain GaAs/Ge/In0.35Ga0.65As/GaAs quantum wells heterostructure optimized in terms of compositions and thicknesses is studied by solving Schrodinger equation as well as the absorption coefficient (>1.5 x 10(4) cm(-1)). These computations have been used for the study of p-i-n infrared photodetectors operating at room temperature in the range 13-1.55 mu m. The electron transport in the GaAs/Ge/In0.35Ga0.65As/GaAs multi-quantum wells-based p-i-n structure was analyzed and numerically simulated taking into account tunneling process and thermally activated transfer through the barriers mainly. The temperature dependence of dark current mechanisms and zero-bias resistance area product (R(0)A) have been analyzed. Extracted from current-voltage characteristics, R(0)A products above 3.6.10(6) Omega cm(2) at 77 K were calculated, and the quantitative analysis of the J-V curves showed that the dark current density of Ge/In0.35Ga0.65As photodetector is dominated by generation-recombination processes. The suitability of the modeled photodetector is approved by its feasibility of achieving good device performance near room temperature operating at 1.55 mu m. Quantum efficiency of similar to 90% and responsivity similar to 0.6 A/W, have been achieved. (C) 2015 Elsevier B.V. All rights reserved.

关键词： Band engineering Absorption Strained Ge/InxGa1-xAs Infrared photodetector Dark current

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Results and developments from the 12m Davies-Cotton Medium-Sized Telescope prototype for the Cherenkov Telescope Array 7

Results and developments from the 12m Davies-Cotton Medium-S...

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Conference on Optics for EUV, X-Ray, and Gamma-Ray Astronomy Vii as part of the SPIE Optics + Photonics International Symposium on optical engineering + Applications

作者： Oakes, Louise Garczarczyk, Markus Schlenstedt, Stefan Sternberger, Ronny Schwanke, Ullrich Humboldt Univ Berlin Germany DESY Zeuthen Germany

ISBN: (纸本)9781628417692

The Cherenkov Telescope Array (CTA) will be the next generation ground-based observatory for gamma-ray astronomy, covering an energy range from a few tens of GeV to a few hundred TeV. The CTA project is currently in the design and prototyping phase, the start of construction is planned for 2016. The planned sensitivity of CTA improves on current ground based Cherenkov telescope experiments by about an order of magnitude. In the core energy range this sensitivity will be dominated by up to 40 Medium-Sized Telescopes (MSTs). These telescopes, of a modified Davies-Cotton mount type with a reflector diameter of 12 m, are currently being prototyped. A full-size mechanical prototype has been operating in Berlin since 2012. Several types of prototype mirrors have been developed and tested, and are mounted on the telescope. CCD cameras with various lenses are mounted on the prototype for studying deformation of the structure, testing alignment techniques, and telescope pointing using astrometry methods. The report will focus on results of optical and structural measurements, commissioning and testing of the MST prototype in Berlin, as well as the final design.

关键词： CTA Cherenkov Telescope MST Davies-Cotton

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Operational perspective of remote sensing-based forest fire danger forecasting systems

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ISPRS JOURNAL OF PHOTOGRAMMETRY AND REMOTE SENSING 2015年第Jun.期104卷 224-236页

作者： Chowdhury, Ehsan H. Hassan, Quazi K. Univ Calgary Schulich Sch Engn Dept Geomat Engn Calgary AB T2N 1N4 Canada

Forest fire is a natural phenomenon in many ecosystems across the world. One of the most important components of forest fire management is the forecasting of fire danger conditions. Here, our aim was to critically analyse the following issues, (i) current operational forest fire danger forecasting systems and their limitations;(ii) remote sensing-based fire danger monitoring systems and usefulness in operational perspective;(iii) remote sensing-based fire danger forecasting systems and their functional implications;and (iv) synergy between operational forecasting systems and remote sensing-based methods. In general, the operational systems use point-based measurements of meteorological variables (e.g., temperature, wind speed and direction, relative humidity, precipitations, cloudiness, solar radiation, etc.) and generate danger maps upon employing interpolation techniques. Theoretically, it is possible to overcome the uncertainty associated with the interpolation techniques by using remote sensing data. During the last several decades, efforts were given to develop fire danger condition systems, which could be broadly classified into two major groups: fire danger monitoring and forecasting systems. Most of the monitoring systems focused on determining the danger during and/or after the period of image acquisition. A limited number of studies were conducted to forecast fire danger conditions, which could be adaptable. Synergy between the operational systems and remote sensing-based methods were investigated in the past but too much complex in nature. Thus, the elaborated understanding about these developments would be worthwhile to advance research in the area of fire danger in the context of making them operational. (c) 2014 International Society for Photogrammetiy and Remote Sensing, Inc. (ISPRS) Published by Elsevier B.V. All rights reserved.

关键词： Fire occurrence Meteorological/environmental variables System development Spatial dynamics optical/thermal/radar imaging

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