Low loss Ge-on-Si waveguides operating in the 8–14 µm atmospheric transmission window

Germanium-on-silicon waveguides were modeled, fabricated and characterized at wavelengths ranging from 7.5 to 11 µm. Measured waveguide losses are below 5 dB/cm for both TE and TM polarization and reach values of ∼ 1 dB/cm for ≥ 10 µm wavelengths for the TE polarization. This work demonstrates experimentally for the first time that Ge-on-Si is a viable waveguide platform for sensing in the molecular fingerprint spectral region. Detailed modeling and analysis is presented to identify the various loss contributions, showing that with practical techniques losses below 1 dB/cm could be achieved across the full measurement range

Sens-Us: Designing Innovative Civic Technology for the Public Good

How can civic technology be designed to encourage more public engagement? What new methods of data collection and sharing can be used to engender a different relationship between citizens and the state? One approach has been to design physical systems that draw people in and which they can trust, leading them to give their views, opinions or other data. So far, they have been largely used to elicit feedback or votes for one or two questions about a given topic. Here, we describe a physical system, called Sens-Us, which was designed to ask a range of questions about personal and sensitive information, within the context of rethinking the UK Census. An in-the-wild study of its deployment in a city cultural center showed how a diversity of people approached, answered and compared the data that had been collected about themselves with others. We discuss the findings in relation to the pros and cons of using this kind of innovative technology when wanting to promote civic engagement or other forms of public engagement

Performance of the rebuilt SUERC single-stage accelerator mass spectrometer

The SUERC bipolar single-stage accelerator mass spectrometer (SSAMS) has been dismantled and rebuilt to accommodate an additional rotatable pre-accelerator electrostatic spherical analyser (ESA) and a second ion source injector. This is for the attachment of an experimental positive-ion electron cyclotron resonance (ECR) ion source in addition to a Cs-sputter source. The ESA significantly suppresses oxygen interference to radiocarbon detection, and remaining measurement interference is now thought to be from 13C injected as 13CH molecule scattering off the plates of a second original pre-detector ESA

SmallTalk: Using tangible interactions to gather feedback from children

Gathering opinions from young children is challenging and different methods have been explored. In this paper we investigated how tangible devices can be used to gather feedback from children in the context of a theater performance. We introduce SmallTalk, a tangible survey system designed for use within a theater space to capture what children, aged 4 to 9, thought of a live performance they had just seen. We describe how the system was designed to build on previous feedback methods that had been tried; while at the same time meeting the constraints of the challenging theater context. We present results from seven deployments of SmallTalk and based on these we briefly discuss its value as a method for evaluating the theater performance. We then look at how the results validated the system design and present several design implications that more generally relate to tangible feedback systems for children

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http://archive.org/details/determinationofc00gallN

Optical properties of highly n-doped germanium obtained by in situ doping and laser annealing

High n-type doping in germanium is essential for many electronic and optoelectronic applications especially for high performance Ohmic contacts, lasing and mid-infrared plasmonics. We report on the combination of in situ doping and excimer laser annealing to improve the activation of phosphorous in germanium. An activated n-doping concentration of 8.8  ×  1019 cm−3 has been achieved starting from an incorporated phosphorous concentration of 1.1  ×  1020 cm−3. Infrared reflectivity data fitted with a multi-layer Drude model indicate good uniformity over a 350 nm thick layer. Photoluminescence demonstrates clear bandgap narrowing and an increased ratio of direct to indirect bandgap emission confirming the high doping densities achieved

Mid-Infrared Plasmonic Platform Based on n-Doped Ge-on-Si: Molecular Sensing with Germanium Nano-Antennas on Si

CMOS-compatible, heavily-doped semiconductor films are very promising for applications in mid-infrared plasmonic devices because the real part of their dielectric function is negative and broadly tunable in this wavelength range. In this work we investigate n-type doped germanium epilayers grown on Si substrates. We design and realize Ge nanoantennas on Si substrates demonstrating the presence of localized plasmon resonances, and exploit them for molecular sensing in the mid-infrared

Towards a Mid-Infrared Lab-on-Chip Sensor using Ge-on-Si Waveguides

For the last decade, germanium has been proposed as an excellent material for passive mid-infrared (MIR) integrated photonics. This technology allows for label-free sensing in the molecular fingerprint regime (6.7–20 μm), where molecules can be uniquely identified by their absorption spectra. Such a platform has the potential to enable low cost, miniaturized mid-infrared sensors for use in crucial applications such as explosives detection, pollution monitoring and detection of breath biomarkers for point of care diagnostics. There have now been a number of demonstrations of waveguides up to 8.5 μm wavelength using Ge [1] and SiGe [2] waveguides. Previously, we have demonstrated the first low loss Ge-on-Si waveguides from 7.5 to 11 μm, with losses as low as ∼1 dB/cm [3]. Here, we demonstrate their potential for sensing applications by evanescently sensing unique vibrations in poly(methyl methacrylate) (PMMA) polymers, in the spectral region of 7.5–10 μm wavelength