Browsing by Author "Lin, Tao"

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Modelling of microcavity effect in InGaN/GaN heterostructures for interfacial study
(2018-08-01)
Liu, Honghui
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Lin, Tao
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Wan, Lingyu
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Xu, Gu
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Kuo, Hao-Chung
Photoluminescence (PL) spectrum provides the most conventional measurement for emission properties of GaN-based light-emitting diodes (LEDs), in which Fabry-Perot oscillations are often observed modulating the emission peaks. A fitting model for PL intensity accounting the microcavity between air/GaN and GaN/sapphire heterostructure was proposed to treat the PL spectra of different GaN-based LEDs, extracting key factors that implied the interfacial optical properties. This approach was successfully verified by measurements of spectroscopic ellipsometry, then was applied to quantitatively analyse the interfacial-defect-related distortion of dielectric properties. The extracted oscillation coefficient is sensitive to the change of interface qualities and reveals the optical properties of internal interfaces. The new method may also be applied to the other heterojunction LEDs.
Neutrino physics with JUNO
(2016-03)
An, Fengpeng
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An, Guangpeng
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An, Qi
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Antonelli, Vito
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Baussan, Eric
The Jiangmen Underground Neutrino Observatory (JUNO), a 20 kton multipurpose underground liquid scintillator detector, was proposed with the determination of the neutrino mass hierarchy (MH) as a primary physics goal. The excellent energy resolution and the large fiducial volume anticipated for the JUNO detector offer exciting opportunities for addressing many important topics in neutrino and astro-particle physics. In this document, we present the physics motivations and the anticipated performance of the JUNO detector for various proposed measurements. Following an introduction summarizing the current status and open issues in neutrino physics, we discuss how the detection of antineutrinos generated by a cluster of nuclear power plants allows the determination of the neutrino MH at a 3-4 sigma significance with six years of running of JUNO. The measurement of antineutrino spectrum with excellent energy resolution will also lead to the precise determination of the neutrino oscillation parameters sin(2) theta(12), Delta m(21)(2), and vertical bar Delta m(ee)(2)vertical bar to an accuracy of better than 1%, which will play a crucial role in the future unitarity test of the MNSP matrix. The JUNO detector is capable of observing not only antineutrinos from the power plants, but also neutrinos/antineutrinos from terrestrial and extra-terrestrial sources, including supernova burst neutrinos, diffuse supernova neutrino background, geoneutrinos, atmospheric neutrinos, and solar neutrinos. As a result of JUNO\'s large size, excellent energy resolution, and vertex reconstruction capability, interesting new data on these topics can be collected. For example, a neutrino burst from a typical core-collapse supernova at a distance of 10 kpc would lead to similar to 5000 inverse-beta-decay events and similar to 2000 all-flavor neutrino-proton ES events in JUNO, which are of crucial importance for understanding the mechanism of supernova explosion and for exploring novel phenomena such as collective neutrino oscillations. Detection of neutrinos from all past core-collapse supernova explosions in the visible universe with JUNO would further provide valuable information on the cosmic star-formation rate and the average core-collapse neutrino energy spectrum. Antineutrinos originating from the radioactive decay of uranium and thorium in the Earth can be detected in JUNO with a rate of similar to 400 events per year, significantly improving the statistics of existing geoneutrino event samples. Atmospheric neutrino events collected in JUNO can provide independent inputs for determining the MH and the octant of the theta(23) mixing angle. Detection of the Be-7 and B-8 solar neutrino events at JUNO would shed new light on the solar metallicity problem and examine the transition region between the vacuum and matter dominated neutrino oscillations. Regarding light sterile neutrino topics, sterile neutrinos with 10-(5) eV(2) < Delta m(41)(2) < 10(-2) and a sufficiently large mixing angle theta(14) could be identified through a precise measurement of the reactor antineutrino energy spectrum. Meanwhile, JUNO can also provide us excellent opportunities to test the eV-scale sterile neutrino hypothesis, using either the radioactive neutrino sources or a cyclotron-produced neutrino beam. The JUNO detector is also sensitive to several other beyondthe-standard-model physics. Examples include the search for proton decay via the p -> K++ <(v)over bar> decay channel, search for neutrinos resulting from dark-matter annihilation in the Sun, search for violation of Lorentz invariance via the sidereal modulation of the reactor neutrino event rate, and search for the effects of non-standard interactions. The proposed construction of the JUNO detector will provide a unique facility to address many outstanding crucial questions in particle and astrophysics in a timely and cost-effective fashion. It holds the great potential for further advancing our quest to understanding the fundamental properties of neutrinos, one of the building blocks of our Universe.
Overview of Screen Content Video Coding: Technologies, Standards, and Beyond
(2016-12)
Peng, Wen-Hsiao
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Walls, Frederick G.
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Cohen, Robert A.
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Xu, Jizheng
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Ostermann, Joern
This paper presents recent advances in screen content video coding, with an emphasis on two state-of-the-art standards: HEVC/H. 265 Screen Content Coding Extensions (HEVC-SCC) by ISO/IEC Moving Picture Experts Group and ITU-T Video Coding Experts Group, and Display Stream Compression (DSC) by Video Electronics Standards Association. The HEVC-SCC enhances the capabilities of HEVC in coding screen content, while DSC provides lightweight compression for display links. Although targeting different application domains, they share some design principles and are expected to become the leading formats in the marketplace in the coming years. This paper provides a brief account of their background, key elements, performance, and complexity characteristics, according to their final specifications. As we survey these standards, we also summarize prior arts in the last decade and explore future research opportunities and standards developments in order to give a comprehensive overview of this field.
Overview of Screen Content Video Coding: Technologies, Standards, and Beyond
(2016-12)
Peng, Wen-Hsiao
;
Walls, Frederick G.
;
Cohen, Robert A.
;
Xu, Jizheng
;
Ostermann, Joern
This paper presents recent advances in screen content video coding, with an emphasis on two state-of-the-art standards: HEVC/H. 265 Screen Content Coding Extensions (HEVC-SCC) by ISO/IEC Moving Picture Experts Group and ITU-T Video Coding Experts Group, and Display Stream Compression (DSC) by Video Electronics Standards Association. The HEVC-SCC enhances the capabilities of HEVC in coding screen content, while DSC provides lightweight compression for display links. Although targeting different application domains, they share some design principles and are expected to become the leading formats in the marketplace in the coming years. This paper provides a brief account of their background, key elements, performance, and complexity characteristics, according to their final specifications. As we survey these standards, we also summarize prior arts in the last decade and explore future research opportunities and standards developments in order to give a comprehensive overview of this field.
Recombination Pathways in Green InGaN/GaN Multiple Quantum Wells
(2017-02-21)
Lin, Tao
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Kuo, Hao Chung
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Jiang, Xiao Dong
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Feng, Zhe Chuan
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光電工程學系
This paper reports the transient photoluminescence (PL) properties of an InGaN/GaN multiple quantum well (MQW) light-emitting diode (LED) with green emission. Recombination of localized excitons was proved to be the main microscopic mechanism of green emission in the sample. The PL dynamics were ascribed to two pathways of the exciton recombination, corresponding to the fast decay and the slow decay, respectively. The origins of slow decay and fast decay were assigned to local compositional fluctuations of indium and thickness variations of InGaN layers, respectively. Furthermore, the contributions of two decay pathways to the green PL were found to vary at different emission photon energy. The fraction of fast decay pathway decreased with decreasing photon energy. The slow radiative PL from deep localized exciton recombination suffered less suppression from non-radiative delocalization process, for the higher requested activation energy. All these results supported a clear microscopy mechanism of excitation-emission process of the green MQW LED structure.