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Studies on the electronic structures of three-dimensional topological insulators by angle resolved photoemission spectroscopy

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Frontiers of physics 2012年第2期7卷 175-192页

作者： Yulin Chen (1) (2) (3) 1. Department of Physics University of Oxford Clarendon Laboratory Parks Road Oxford OX1 3PU UK2. Stanford Institute for Materials and Energy Sciences SLAC National Accelerator Laboratory 2575 Sand Hill Road Menlo Park CA 94025 USA3. Geballe Laboratory for Advanced Materials Departments of Physics and Applied Physics Stanford University Stanford CA 94305 USA

Three-dimensional （3D） topological insulators represent a new state of quantum matter with a bulk gap and odd number of relativistic Dirac fermions on the surface. The unusual surface states of topological insulators rise from the nontrivial topology of their electronic structures as a result of strong spin-orbital coupling. In this review, we will briefly introduce the concept of topological insu- lators and the experimental method that can directly probe their unique electronic structure： angle resolved photoemission spectroscopy （ARPES）. A few examples are then presented to demonstrate the unique band structures of different families of topological insulators and the unusual properties of the topological surface states. Finally, we will briefly discuss the future development of topological quantum materials.

关键词： topological insulator (TI) photoemission ARPES

Slow and fast light in quantum-well and quantum-dot semiconductor optical amplifiers Invited Paper

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Chinese Optics Letters 2008年第10期6卷 736-742页

作者： Piotr Konrad Kondratko Akira Matsudaira Department of Electrical and Computer Engineering University of Illinois at Urbana-ChampaignUrbana IL61801USA

Slow and fast light in quantum-well （QW） and quantum-dot （QD） semiconductor optical amplifiers （SOAs） using nonlinear quantum optical effects are presented. We demonstrate electrical and optical controls of fast light using the coherent population oscillation （CPO） and four wave mixing （FWM） in the gain regime of QW SOAs. We then consider the dependence on the wavelength and modal gain of the pump in QW SOAs. To enhance the tunable photonic delay of a single QW SOA, we explore a serial cascade of multiple amplifiers. A model for the number of QW SOAs in series with variable optical attenuation is developed and matched to the experimental data. We demonstrate the scaling law and the bandwidth control by using the serial cascade of multiple QW SOAs. Experimentally, we achieve a phase change of 160^o and a scaling factor of four at 1 GHz using the cascade of four QW SOAs. Finally, we investigate CPO and FWM slow and fast light of QD SOAs. The experiment shows that the bandwidth of the time delay as a function of the modulation frequency changes in the absorption and gain regimes due to the carrier-lifetime variation. The tunable phase shift in QD SOA is compared between the ground- and first excited-state transitions with different modal gains.

关键词： SOA CPO Slow and fast light in quantum-well and quantum-dot semiconductor optical amplifiers Invited Paper FWM well

A critique of reliability prediction techniques for avionics applications

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Chinese Journal of Aeronautics 2018年第1期31卷 10-20页

作者： Guru Prasad PANDIAN Diganta DAS Chuan LI Enrico ZIO Michael PECHT Center for Advanced Life Cycle Engineering University of MarylandCollege Park National Research Base of Intelligent Manufacturing Service Chongqing Technology and Business University Chaire System Science and the Energy Challenge-Fondation Electricite’de France Centrale Supelec Department of Energy Politecnico di Milano

Avionics （aeronautics and aerospace） industries must rely on components and systems of demonstrated high reliability. For this, handbook-based methods have been traditionally used to design for reliability, develop test plans, and define maintenance requirements and sustainment logistics, However, these methods have been criticized as flawed and leading to inaccurate and mis- leading results. In its recent report on enhancing defense system reliability, the U.S. National Academy of Sciences has recently discredited these methods, judging the Military Handbook （MIL- HDBK-217） and its progeny as invalid and inaccurate. This paper discusses the issues that arise with the use of handbook-based methods in commercial and military avionics applications. Alter- native approaches to reliability design （and its demonstration） are also discussed, including similarity analysis, testing, physics-of-failure, and data analytics for prognostics and systems health management.

关键词： Avionics reliability Handbook-based methods MIL-HDBK-217 Physics of failure Prognostics and health management

System-level Pareto frontiers for on-chip thermoelectric coolers

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Frontiers in Energy 2018年第1期12卷 109-120页

作者： Sevket U. YURUKER Michael C. FISH Zhi YANG Nicholas BALDASARO Philip BARLETTA Avram BAR-COHEN Bao YANG Department of Mechanical Engineering University of MarylandCollege Park MD 20742 USA Research Triangle Institute Research Triangle Park NC 27709 USA Micross Components Research Triangle Park NC 27709 USA

The continuous rise in heat dissipation of integrated circuits necessitates advanced thermal solutions to ensure system reliability and efficiency. Thermoelectric coolers are among the most promising techniques for dealing with localized on-chip hot spots. This study focuses on establishing a holistic optimization methodol- ogy for such thermoelectric coolers, in which a thermo- electric element＇s thickness and the electrical current are optimized to minimize source temperature with respect to ambient, when the thermal and electrical parasitic effects are considered. It is found that when element thickness and electrical current are optimized for a given system architecture, a ＂heat flux vs. temperature difference＂ Pareto frontier curve is obtained, indicating that there is an optimum thickness and a corresponding optimum current that maximize the achievable temperature reduc- tion while removing a particular heat flux. This methodol- ogy also provides the possible system level AT＇s that can be achieved for a range of heat fluxes, defining the upper limits of thermoelectric cooling for that architecture. In this study, use was made of an extensive analytical model, which was verified using commercially available finite element analysis software. Through the optimization process, 3 pairs of master curves were generated, which were then used to compose the Pareto frontier for any given system architecture. Finally, a case study wasperformed to provide an in-depth demonstration of the optimization procedure for an example application.

关键词： thermoelectric cooling thermal management,optimization high flux electronics

Hybrid silicon modulators

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Chinese Optics Letters 2009年第4期7卷 280-285页

作者： J.E.Bowers Department of Electrical and Computer Engineering University of California Santa Barbara

A number of active elements have been demonstrated using the hybrid silicon evanescent platform, including lasers, amplifiers, and detectors. In this letter, two types of hybrid silicon modulators, flflfilling the building blocks in optical communication on this platform, are presented. A hybrid silicon electroabsorp- tion modulator, suitable for high speed interconnects, with 10-dB extinction ratio at -5 V and 16-GHz modulation bandwidth is demonstrated. In addition, a hybrid silicon Mach-Zehnder modulator utilizing carrier depletion in multiple quantum wells is proved with 2 *** voltage-length product, 150-nm optical bandwidth, and a large signal modulation up to 10 Gb/s.

关键词： Bandwidth Electroabsorption modulators Modulation Modulators Optical communication Quantum well lasers Semiconducting indium compounds Semiconductor quantum wells Silicon Silicon detectors

One-Dimensional ZnO Nanostructures： Solution Growth and Functional Properties

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Nano Research 2011年第11期4卷 1013-1098页

作者： Sheng Xu Zhong Lin Wang School of Materials Science and Engineering Georgia Institute of Technology Atlanta Georgia 30332-0245 USA

One-dimensional （1D） ZnO nanostructures have been studied intensively and extensively over the last decade not only for their remarkable chemical and physical properties, but also for their diverse current and future technological applications. This article gives a comprehensive overview of the progress that has been made within the context of 1D ZnO nanostructures synthesized via wet chemical methods. We will cover the synthetic methodologies and the corresponding growth mechanisms, various nanostructures grown, their doping and alloying, and position-controlled growth on substrates. Finally, we will review their functional properties in catalysis, hydrophobic surface modification, sensing, and electronic, optical, optoelectronic, and energy harvesting devices.

关键词： ZnO one dimensional nanostructures solution growth electronic optical optoelectronic energy harvesting devices

A tunable ferroelectric based unreleased RF resonator

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Microsystems & Nanoengineering 2020年第1期6卷 1334-1340页

作者： Yanbo He Bichoy Bahr Mengwei Si Peide Ye Dana Weinstein Purdue University West LafayetteINUSA Kilby Labs Texas InstrumentsDallasTXUSA

This paper introduces the first tunable ferroelectric capacitor(FeCAP)-based unreleased RF MEMS resonator,integrated seamlessly in Texas Instruments’130 nm Ferroelectric RAM(FeRAM)*** designs presented here are monolithically integrated in solid-state CMOS technology,with no post-processing or release step typical of other MEMS *** array of FeCAPs in this complementary metal-oxide-semiconductor(CMOS)technology’s back-end-of-line(BEOL)process were used to define the acoustic resonance cavity as well as the electromechanical *** achieve high quality factor(Q)of the resonator,acoustic waveguiding for vertical confinement within the CMOS stack is studied and *** design considerations are discussed to obtain lateral confinement and suppression of spurious *** FeCAP resonator is demonstrated with fundamental resonance at 703 MHz and Q of *** gives a frequency-quality factor product f·Q=7:11×10^(11) which is 1.6×higher than the most state-of-the-art Pb(Zr,Ti)O_(3)(PZT)*** to the ferroelectric characteristics of the FeCAPs,transduction of the resonator can be switched on and off by adjusting the electric *** this case,the resonance can be turned off completely at±0.3 V corresponding to the coercive voltage of the constituent FeCAP *** novel switchable resonators may have promising applications in on-chip timing,ad-hoc radio front ends,and chip-scale sensors.

关键词： resonator tunable switched

Ultrasonically actuated neural probes for reduced trauma and inflammation in mouse brain

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Microsystems & Nanoengineering 2022年第6期8卷 137-151页

作者： Po-Cheng Chen Catharine G.Young Chris B.Schaffer Amit Lal SonicMEMS Laboratory School of Electrical and Computer EngineeringCornell UniversityIthacaNYUSA Meinig School of Biomedical Engineering Cornell UniversityIthacaNYUSA

Electrical neural recordings measured using direct electrical interfaces with neural tissue suffer from a short lifespan because the signal strength decreases over *** inflammatory response to the inserted microprobe can create insulating tissue over the electrical interfaces,reducing the recorded signal below noise *** of the factors contributing to this inflammatory response is the tissue damage caused during probe ***,we explore the use of ultrasonic actuation of the neural probe during insertion to minimize tissue damage in *** neural microprobes were designed and fabricated with integrated electrical recording sites and piezoelectric *** microprobes were actuated at ultrasonic frequencies using integrated piezoelectric *** microprobes were inserted into mouse brains under a glass window over the brain surface to image the tissue surrounding the probe using two-photon *** mechanical force required to penetrate the tissue was reduced by a factor of 2–3 when the microprobe was driven at ultrasonic *** histology at the probe insertion site showed a reduced area of damage and decreased microglia counts with increasing ultrasonic actuation of the *** imaging of the microprobe over weeks demonstrated stabilization of the inflammatory *** of electrical signals from neurons over time suggests that microprobes inserted using ultrasound have a higher signal-tonoise ratio over an extended time period.

关键词： microprobe insertion electrical

WISH:wavefront imaging sensor with high resolution

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Light(Science & Applications) 2019年第1期8卷 818-827页

作者： Yicheng Wu Manoj Kumar Sharma Ashok Veeraraghavan Department of Electrical and Computer Engineering Rice UniversityHoustonTXUSA Applied Physics Program Rice UniversityHoustonTXUSA

Wavefront sensing is the simultaneous measurement of the amplitude and phase of an incoming optical *** wavefront sensors such as Shack-Hartmann wavefront sensor(SHWFS)suffer from a fundamental tradeoff between spatial resolution and phase estimation and consequently can only achieve a resolution of a few thousand *** break this tradeoff,we present a novel computational-imaging-based technique,namely,the Wavefront Imaging Sensor with High resolution(WISH).We replace the microlens array in SHWFS with a spatial light modulator(SLM)and use a computational phase-retrieval algorithm to recover the incident *** wavefront sensor can measure highly varying optical fields at more than 10-megapixel resolution with the fine phase *** the best of our knowledge,this resolution is an order of magnitude higher than the current noninterferometric wavefront *** demonstrate the capability of WISH,we present three applications,which cover a wide range of spatial ***,we produce the diffraction-limited reconstruction for long-distance imaging by combining WISH with a large-aperture,low-quality Fresnel ***,we show the recovery of high-resolution images of objects that are obscured by ***,we show that WISH can be used as a microscope without an objective *** study suggests that the designing principle of WISH,which combines optical modulators and computational algorithms to sense high-resolution optical fields,enables improved capabilities in many existing applications while revealing entirely new,hitherto unexplored application areas.

关键词： estimation. field. resolution