High-Q optical resonators in silicon-on-insulator-based slot waveguides

This letter describes the design, fabrication and characterization of high-Q oval resonators based on slot waveguide geometries in thin silicon-on-insulator material. Optical quality factors of up to 27 000 were measured in such filters, and we estimate losses of –10 dB/cm in the slotted waveguides on the basis of our resonator measurements. Such waveguides enable the concentration of light to very high optical fields within nanoscale dimensions, and show promise for the confinement of light in low-index material with potential applications for optical modulation, nonlinear optics and optical sensing

Integrated plasmon and dielectric waveguides

We have designed, fabricated and characterized surface plasmon waveguides for near infrared light in the telecommunications spectrum. These waveguides exhibit losses of -1.2dB/μm and can guide light around 0.5 μm bends. Light can also be efficiently coupled between more conventional silicon waveguides and these plasmon waveguides with compact couplers, and we demonstrate that surface plasmon optical devices can be constructed by using planar circuit fabrication techniques. The large optical field enhancements of metallic surface plasmon devices are expected to lead to a new class of plasmonic optical devices, which will take advantage of the large field enhancements at the surfaces of the plasmon waveguides for nonlinear or sensing functionality, while utilizing the low losses available in silicon waveguides to move light longer distances on chip

High-Q ring resonators in thin silicon-on-insulator

We have fabricated high-Q microrings from thin silicon-on-insulater SOI layers and measured Q values of 45 000 in these rings, which were then improved to 57 000 by adding a PMMA cladding. The optimal waveguide designs were calculated, and the waveguide losses were analyzed. These high-Q resonators are expected to lead to interesting devices for telecommunication filters and sources as well as optical refractive index sensing

Beyond Migration: Understanding the Effects of Repository Migration on User Experiences and Repository Services

Change is inevitable. As repository systems evolve, institutions may evaluate whether or not their current and future repository needs will be met. If they are not met, an institution may decide to migrate repository platforms. But repository systems are not agnostic. In many cases, repositories will offer completely different user experiences, services, functionality, and capabilities. Inevitably, an institution will need to evaluate what will be gained or loss due to a repository migration. What should an institution do if key functionality, such as discovery, were broken because of a migration? What could be learned from the current migration, or what additional services and functionality would a new repository present, that would aid in future migrations? In 2018, the Carnegie Mellon University Libraries migrated 33,000 items from their former Digital Commons repository to their new figshare for institutions repository. Additionally, a number of materials were migrated to other institutions where those materials were better suited to be housed. This presentation will discuss the evaluation of repository gains and losses created by the migration. Additionally, this presentation will highlight what additional projects were necessary to ensure that user services and discovery could be directed to the new locations of the content

Analysis of the Tuning Sensitivity of Silicon-on-Insulator Optical Ring Resonators

High-quality-factor optical ring resonators have recently been fabricated in thin silicon-on-insulator (SOI). Practical applications of such devices will require careful tuning of the precise location of the resonance peaks. In particular, one often wants to maximize the resonance shift due to the presence of an active component and minimize the resonance shift due to temperature changes. This paper presents a semianalytic formalism that allows the prediction of such resonance shifts from the waveguide geometry. This paper also presents the results of experiments that show the tuning behavior of several ring resonators and find that the proposed semianalytic formalism agrees with the observed behavior

Segmented waveguides in thin silicon-on-insulator

We have developed new silicon-on-insulator waveguide designs for simultaneously achieving both low-loss optical confinement and electrical contacts, and we present a design methodology based on calculating the Bloch modes of such segmented waveguides. With this formalism, waveguides are designed in a single thin layer of silicon-on-insulator to achieve both optical confinement and minimal insertion loss. Waveguides were also fabricated and tested, and the measured data were found to closely agree with theoretical predictions, demonstrating input insertion loss and propagation loss better than 0.1 dB and -16 dB/cm, respectively

Concert recording 2016-04-09c

[Track 01]. Into the air / Ivan Trevino -- [Track 02]. Preludes. II ; [Track 03]. III ; [Track 04]. I / Michael Burritt -- [Track 05]. Arabesque no. 2 / Claude Debussy ; arranged by Caleb Evans -- [Track 06]. Somewhere over the rainbow / Harold Arlen ; arranged by Max Seide Leth -- [Track 07]. Pure imagination / Leslie Bricusse and Anthony Newly ; arranged by Alex Stopa -- [Track 08]. Claire de lune / Claude Debussy ; arranged by Nick Baron -- [Track 09]. Trio per uno. II ; [Track 10]. I / Nebosja Zivkovic

Concert recording 2016-05-01a

[Track 01]. Third rail / John Ling -- [Track 02]. Electric thoughts / Ivan Trevino -- [Track 03]. Vespertine formations / Christopher Deane -- [Track 04]. Fear cage / Kirk J. Gay -- [Track 05]. One summary / John Psathas -- [Track 06]. War drum peace drum / David Reeves

Stable carbon isotope signatures of ancient Maize agriculture at El Kinel, Guatemala

Abstract Stable C isotope studies of the soil organic matter (SOM) have delineated areas with histories of vegetation change from C3 forest to C4 maize (Zea mays L.) agriculture and back to the contemporary C3 forest. The objectives of this study were to: (1) determine if land around El Kinel, Guatemala possessed a vegetative history of shifts from C3 forest to C4 maize agriculture in the past, (2) determine if 10 years of contemporary maize production is sufficient time to deposit an isotopic signature of C4 plants in the root zone (top 40 cm), and (3) to examine the extractable phosphorus concentrations and δ13C in soils of important archaeological features that included a midden, a burial, and two ancient reservoirs (aguadas). The lack of a shift in δ13C greater than 3.5‰ in the top 40 cm of the contemporary maize field suggested that continual maize cultivation of more than ten years is required to create an isotopic signature for maize agriculture. Carbon isotopic evidence was found in soil profiles to confirm that long-term agriculture was practiced by ancient Maya farmers at El Kinel. The man-made aguadas did not show isotopic shifts greater than 2.3‰ in any part of the profile, indicating they were used for other purposes not associated with C4 plant growth. The relatively low P (−1) was found in soil at the same depth but at a distance of 30 cm from an ancient burial. The high P concentration (127 mg kg−1) found within millimeters of the bones implied that the P enrichment came from the remains but P remained fixed in the soil and did not migrate