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Tailoring Second Harmonic Diffraction in GaAs Metasurfaces via Crystal Orientation

2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings

Vabishchevich, P.P.; Vaskin, A.; Addamane, S.; Liu, S.; Sharma, A.P.; Balakrishnan, G.; Reno, John L.; Keeler, G.A.; Sinclair, Michael B.; Staude, I.; Brener, Igal

We use GaAs metasurfaces with (111) crystal orientation to channel the second harmonic generation (SHG) into the zero-diffraction order that is suppressed for SHG obtained from GaAs metasurfaces with (100) orientation.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Phase optimization of a silicon photonic two-dimensional electro-optic phased array

2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings

Gehl, Michael; Hoffman, Galen; Davids, Paul; Starbuck, Andrew L.; Dallo, Christina; Long, Christopher M.; Barber, Zeb; Kadlec, Emil; Mohan, R.K.; Crouch, Stephen

Phase errors in large optical phased arrays degrade beam quality and must be actively corrected. Using a novel, low-power electro-optic design with matched pathlengths, we demonstrate simplified optimization and reduced sensitivity to wavelength and temperature.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

A Uniform Practice for Conceptualizing and Communicating Food-Energy-Water Nexus Studies

Earth's Future

Gunda, Thushara

There is growing interest in nexus research: energy-water, energy-water-land, and more recently food-energy-water. Motivating this movement is the recognition that the dynamics and feedbacks that constitute these nexuses have been overlooked in the past but are critical to the planning and management of these interacting elements. Formal reviews have identified gaps in current studies. In this commentary, we highlight additional oversights that are hindering integration of findings in nexus studies, notably usage of imprecise terminology to describe analyses, a failure to close the loop by linking production with corresponding waste streams, and exclusion of dynamics linking diverse constituent elements. Equally lacking from current nexus studies is a consistent protocol for communicating the conceptual basis of our studies. To fill this gap, we draw on diverse perspectives and fields to propose a comprehensive and systematic framework that can guide the model conceptualization phase of nexus studies. We also present a standardized documentation practice (similar to one utilized by the agent-based modeling community) to facilitate communication of nexus studies. These initiatives can improve our ability to account for and communicate the nuanced, food-energy-water nexus interactions in a consistent manner, which is necessary to better inform risk analysis and avoid decisions with unintended consequences and hidden costs to society.

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TYPE Journal Article YEAR 2019
DOIOSTIScopus

Position-Dependent Transport of n-p-n Junctions in Axially Doped SiGe Nanowire Transistors

IEEE Electron Device Letters

Delker, Collin J.; Yoo, Jinkyoung; Swartzentruber, Brian; Harris, Charles T.

Nanowire transistors are typically undoped devices whose characteristics depend strongly on the injection of carriers from the electrical contacts. In this letter, we fabricate and characterize SiGe nanowire transistors with an n-p-n doping profile and with a top gate covering only the p-doped section of the nanowire. For each device, we locate the p-segment with scanning capacitance microscopy, where the p-segment position varies along the channel due to the stochastic nature of our dropcast fabrication technique. The current-voltage characteristics for a series of transistors with different gate positions reveal that the on/off ratios for electrons is the highest when the gated p-type section is closest to the source contact, whereas the on/off ratios for holes is the highest when the gated p-type section is closest to the drain contact.

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TYPE Presentation YEAR 2019
DOIOSTIScopus

Silicon Photonic Single-Sideband Generation with Dual-Parallel Mach-Zehnder Modulators

2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings

Kodigala, Ashok; Gehl, Michael; Derose, C.T.; Hood, D.; Pomerene, A.T.; Dallo, Christina; Trotter, Douglas C.; Moore, P.; Starbuck, Andrew L.; Lee, Jongmin; Biedermann, Grant; Lentine, Anthony L.

We demonstrate the first silicon photonic single-sideband (SSB)modulator with dual-parallel Mach-Zehnder modulators (MZMs)operating near 1550 nm with a measured carrier suppression of 27 dB and at least 12 dB sideband suppression at 1 GHz.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

All-Optical Tuning of Fano Resonances in Broken Symmetry GaAs Metasurfaces

2019 Conference on Lasers and Electro-Optics, CLEO 2019 - Proceedings

Karl, Nicholas J.; Vabishchevich, P.P.; Liu, Sheng; Sinclair, Michael B.; Keeler, Gordon A.; Peake, Gregory M.; Brener, Igal

We demonstrate ultrafast tuning of Fano resonances in a broken symmetry III-V metasurface using optical pumping. The resonance is spectrally shifted by 10 nm under low pump fluences of < 100 uJ.cm-2.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus

Fuzzy matching: Hardware accelerated MPI communication middleware

Proceedings - 19th IEEE/ACM International Symposium on Cluster, Cloud and Grid Computing, CCGrid 2019

Dosanjh, Matthew G.F.; Schonbein, Whit; Grant, Ryan; Bridges, Patrick G.; Gazimirsaeed, S.M.; Afsahi, Ahmad

Contemporary parallel scientific codes often rely on message passing for inter-process communication. However, inefficient coding practices or multithreading (e.g., via MPI-THREAD-MULTIPLE) can severely stress the underlying message processing infrastructure, resulting in potentially un-acceptable impacts on application performance. In this article, we propose and evaluate a novel method for addressing this issue: 'Fuzzy Matching'. This approach has two components. First, it exploits the fact most server-class CPUs include vector operations to parallelize message matching. Second, based on a survey of point-to-point communication patterns in representative scientific applications, the method further increases parallelization by allowing matches based on 'partial truth', i.e., by identifying probable rather than exact matches. We evaluate the impact of this approach on memory usage and performance on Knight's Landing and Skylake processors. At scale (262,144 Intel Xeon Phi cores), the method shows up to 1.13 GiB of memory savings per node in the MPI library, and improvement in matching time of 95.9%; smaller-scale runs show run-time improvements of up to 31.0% for full applications, and up to 6.1% for optimized proxy applications.

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TYPE Conference Poster YEAR 2019
DOIOSTIScopus
Results 25201–25400 of 101,000
Results 25201–25400 of 101,000
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