Mapping the optical properties of slab-type two-dimensional photonic crystal waveguides

We report on systematic experimental mapping of the transmission properties of two-dimensional silicon-on-insulator photonic crystal waveguides for a broad range of hole radii, slab thicknesses and waveguide lengths for both TE and TM polarizations. Detailed analysis of numerous spectral features allows a direct comparison of experimental data with 3D plane wave and finite-difference time-domain calculations. We find, counter-intuitively, that the bandwidth for low-loss propagation completely vanishes for structural parameters where the photonic band gap is maximized. Our results demonstrate that, in order to maximize the bandwidth of low-loss waveguiding, the hole radius must be significantly reduced. While the photonic band gap considerably narrows, the bandwidth of low-loss propagation in PhC waveguides is increased up to 125nm with losses as low as 8$\pm$2dB/cm.Comment: 10 pages, 8 figure

Mode mixing in asymmetric double trench photonic crystal waveguides

e investigate both experimentally and theoretically the waveguiding properties of a novel double trench waveguide where a conventional single-mode strip waveguide is embedded in a two dimensional photonic crystal (PhC) slab formed in silicon on insulator (SOI) wafers. We demonstrate that the bandwidth for relatively low-loss (50dB/cm) waveguiding is significantly expanded to 250nm covering almost all the photonic band gap owing to nearly linear dispersion of the TE-like waveguiding mode. The flat transmission spectrum however is interrupted by numerous narrow stop bands. We found that these stop bands can be attributed to anti-crossing between TE-like (positive parity) and TM-like (negative parity) modes. This effect is a direct result of the strong asymmetry of the waveguides that have an upper cladding of air and lower cladding of oxide. To our knowledge this is the first demonstration of the effects of cladding asymmetry on the transmission characteristics of the PhC slab waveguides.Comment: 7 pages, 6 figure

Latin America and the Debate Over Environmental Protection and National Security

DRMI Working Paper SeriesThe series is intended to convey the preliminary results of [DRMI] ongoing research. The research described in these papers is preliminary and has not completed the usual review process for Institute publications. We welcome feedback from readers and encourage you to convey your comments and criticisms directly to the authors

Designing Emergency Response Dispatch Systems for Better Dispatcher Performance

Emergency response systems are a relatively new and important area of research in the information systems community. While there is a growing body of literature in this research stream, human-computer interaction (HCI) issues concerning the design of emergency response system interfaces have received limited attention. Emergency responders often work in time pressured situations and depend on fast access to key information. One of the problems studied in HCI research is the design of interfaces to improve user information selection and processing performance. Based on cue-summation theory and research findings on parallel processing, associative processing, and hemispheric differences in information processing, this study proposes that information selection of target information in an emergency response dispatch application can be improved by using supplementary cues. Color-coding and sorting are proposed as relevant cues that can improve processing performance by providing prioritization heuristics. An experimental emergency response dispatch application is developed, and user performance is tested under conditions of varying complexity and time pressure. The results suggest that supplementary cues significantly improve performance, with better results often obtained when both cues are used. Additionally, the use of these cues becomes more beneficial as time pressure and task complexity increase

Designing Emergency Response Applications for Better Performance

Emergency responders often work in time pressured situations and depend on fast access to key information. One of the problems studied in human-computer interaction (HCI) research is the design of interfaces to improve user information selection and processing performance. Based on prior research findings this study proposes that information selection of target information in emergency response applications can be improved by using supplementary cues. The research is motivated by cue-summation theory and research findings on parallel and associative processing. Color-coding and location-ordering are proposed as relevant cues that can improve ERS processing performance by providing prioritization heuristics. An experimental ERS is developed users’ performance is tested under conditions of varying complexity and time pressure. The results suggest that supplementary cues significantly improve performance, with the best results obtained when both cues are used. Additionally, the use of these cues becomes more beneficial as time pressure and complexity increase

Modelling the Hosting Capacity of Orion's Low Voltage Network for EV Charging

Forecasting future electricity demand on low voltage (LV) distribution networks is particularly challenging in the face of new technologies such as Electric Vehicles (EVs) where the uptake and charging behaviours are highly uncertain. To support their planning processes, Orion has undertaken a staged assessment of LV network performance in the face of increasing levels of EV charging. The first stage of EV modelling involved a high-level deterministic simulation of all Orion’s LV networks to identify areas that may be more vulnerable to constraints. From the results of the first stage, a smaller subset of vulnerable LV networks was selected for further modelling. This paper focuses on the second stage of the assessment process where 236 selected distribution transformers and their downstream LV networks were modelled using a probabilistic methodology developed by the EPECentre. This model captures a wide range of scenarios and encompasses data from New Zealand-centric inputs, including national travel surveys, household smart meter demand profiles and the current NZ EV fleet composition. In order to meet the large simulation burden required of a probabilistic methodology, a fast power flow solver was developed. This paper reports the forecast congestion levels and probabilities that these selected circuits may face as EV charging increases on Orion’s network. The learnings and challenges of working with imperfect distribution asset data sets to develop these models are also shared, such as approximating LV phase imbalance and electricity demand profiles with only the LV distribution transformer’s Maximum Demand Indicator (MDIs) measurements

Probing the interface state densities near band edges from inductively coupled measurements of sheet resistance

In this work, we report a new approach to characterise interface state density (Dit) near the band edges. Interface defect states are known to trap charge carriers via SRH statistics. At dielectric-silicon interfaces charge in the dielectric layer is neutralised by a layer of mirroring carriers in bulk Si, resulting in an accumulation or inversion layer. Since the interface state density increases exponentially towards the band edge, these states can store large concentrations of charge and alter the carrier concentration at the semiconductor surface. This dramatically influences the operation of devices based on surface carrier manipulation, including field effect passivation, inversion layer pn junctions, and field effect transistors. Unlike capacitive techniques, our method allows a very sensitive detection of the concentration of donor- or acceptor-like states in the unavoidable band-tails. Device simulations show that the conductivity of the charge-induced layer is highly sensitive to Dit near the band-tail but is insensitive to Dit−midgap. Therefore, the wafer resistance detected by inductively coupled measurements is used as a metric to detect band-tail Dit. The wafer resistance is recorded while monitored amounts of surface charges are introduced. The band-tail Dit is extracted by fitting the observed resistance dependence to an accurate model of the system. This method allows probing band-tail Dit near both the conduction and valence band edge on either n-type or p-type silicon substrates. Since a lifetime tester is used to record wafer resistance, this technique provides an easy and accurate detection of band-tail Dit. This technique is highly relevant for analysis of photovoltaic devices since it provides a route to better understand the properties of semiconductor-dielectric interfaces crucial to cell operation

Comparative physiology of Australian quolls (Dasyurus; Marsupialia)

Quolls (Dasyurus) are medium-sized carnivorous dasyurid marsupials. Tiger (3,840 g) and eastern quolls (780 g) are mesic zone species, northern quolls (516 g) are tropical zone, and chuditch (1,385 g) were once widespread through the Australian arid zone. We found that standard physiological variables of these quolls are consistent with allometric expectations for marsupials. Nevertheless, inter-specific patterns amongst the quolls are consistent with their different environments. The lower T ^sub b^ of northern quolls (34°C) may provide scope for adaptive hyperthermia in the tropics, and they use torpor for energy/water conservation, whereas the larger mesic species (eastern and tiger quolls) do not appear to. Thermolability varied from little in eastern (0.035°C °C^sup -1^) and tiger quolls (0.051°C ºC^sup -1^) to substantial in northern quolls (0.100°C ºC^sup -1^) and chuditch (0.146°C ºC^sup -1^), reflecting body mass and environment. Basal metabolic rate was higher for eastern quolls (0.662 ± 0.033 ml O^sub 2^ g^sup -1^ h^sup -1^), presumably reflecting their naturally cool environment. Respiratory ventilation closely matched metabolic demand, except at high ambient temperatures where quolls hyperventilated to facilitate evaporative heat loss; tiger and eastern quolls also salivated. A higher evaporative water loss for eastern quolls (1.43 ± 0.212 mg H^sub 2^O g^sup -1^ h^sup -1^) presumably reflects their more mesic distribution. The point of relative water economy was low for tiger (-1.3°C), eastern (-12.5°C) and northern (+3.3) quolls, and highest for the chuditch (+22.6°C). We suggest that these differences in water economy reflect lower expired air temperatures and hence lower respiratory evaporative water loss for the arid-zone chuditch relative to tropical and mesic quolls