Small signal modulation of photonic crystal surface emitting lasers.

We report the small-signal characterization of a PCSEL device, extracting damping factors and modulation efficiencies, and demonstrating -3 dB modulation bandwidths of up to 4.26 GHz. Based on modelling we show that, by reducing the device width and improving the active region design for high-speed modulation, direct modulation frequencies in excess of 50 GHz are achievable.

Increase in terahertz-wave intensity in a magnetic field due to difference-frequency mixing by exciton excitation in a GaAs/AlAs multiple quantum well.

Magnetic fields can increase the intensity of terahertz (THz) waves due to changing the dipole moment direction using the Lorentz force. This study reports the increase in the THz-wave intensity generated by differential frequency mixing using commercial permanent magnets under exciton-excitation. While a weak magnetic field applied to a multiple quantum well increases the THz-wave intensity due to excitons, a strong field causes its decrease.

CuO-Based Electrochemical Biosensor for Non-Invasive and Portable Glucose Detection.

Electrochemical voltammetric sensors are some of the most promising types of sensors for monitoring various physiological analytes due to their implementation as non-invasive and portable devices. Advantages in reduced analysis time, cost-effectiveness, selective sensing, and simple techniques with low-powered circuits distinguish voltammetric sensors from other methods. In this work, we developed a CuO-based non-enzymatic portable glucose sensor on a graphene paste printed on cellulose cloth.

Increase in terahertz-wave generation by difference frequency mixing by the overlap of exciton states in different GaAs/AlAs quantum wells and spectroscopic measurements.

Intense terahertz-wave emission in the higher frequency region can result in various applications such as terahertz spectroscopy and ultrafast data communication. In this study, an increase in terahertz waves by the overlap of exciton states in different quantum wells and spectroscopic demonstration are reported. The excitation energy dependence of signal intensity shows the effect of the overlap.

Near-infrared and mid-infrared semiconductor broadband light emitters.

Semiconductor broadband light emitters have emerged as ideal and vital light sources for a range of biomedical sensing/imaging applications, especially for optical coherence tomography systems. Although near-infrared broadband light emitters have found increasingly wide utilization in these imaging applications, the requirement to simultaneously achieve both a high spectral bandwidth and output power is still challenging for such devices. Owing to the relatively weak amplified spontaneous emission, as a consequence of the very short non-radiative carrier lifetime of the inter-subband transitions in quantum cascade structures, it is even more challenging to obtain desirable mid-infrared broadband light emitters.

Optimisation of photonic crystal coupling through waveguide design.

This paper considers multiple structural designs for photonic crystal surface emitting lasers operating at key wavelengths. Initially a structure from Williams et al. is modelled, the structure is modified to include an additional GaAs waveguide layer (termed ballast layer) and to include an additional PC layer (termed double decker).

Insights Into Collaborative Networks Of Nonprofit, Private, And Public Organizations That Address Complex Health Issues.

Community networks that include nonprofit, public, and private organizations have formed around many health issues, such as chronic disease management and healthy living and eating. Despite the increases in the numbers of and funding for cross-sector networks, and the growing literature about them, there are limited data and methods that can be used to assess their effectiveness and analyze their designs. We addressed this gap in knowledge by analyzing the characteristics of 260 cross-sector community health networks that collectively consisted of 7,816 organizations during the period 2008-15.

10 GHz pulse repetition rate Er:Yb:glass laser modelocked with quantum dot semiconductor saturable absorber mirror.

Semiconductor saturable absorber mirror (SESAM) modelocked high pulse repetition rate (≥10  GHz) diode-pumped solid-state lasers are proven as an enabling technology for high data rate coherent communication systems owing to their low noise and high pulse-to-pulse optical phase-coherence. Compared to quantum well, quantum dot (QD)-based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the first 10 GHz pulse repetition rate QD-SESAM modelocked laser at 1.

Electronic control of coherence in a two-dimensional array of photonic crystal surface emitting lasers.

We demonstrate a semiconductor PCSEL array that uniquely combines an in-plane waveguide structure with nano-scale patterned PCSEL elements. This novel geometry allows two-dimensional electronically controllable coherent coupling of remote vertically emitting lasers. Mutual coherence of the PCSEL elements is verified through the demonstration of a two-dimensional Young's Slits experiment.

Hospital Contributions to the Delivery of Public Health Activities in US Metropolitan Areas: National and Longitudinal Trends.

Objectives: We investigated changes in hospital participation in local public health systems and the delivery of public health activities over time and assessed the relationship between hospital participation and the scope of activities available in local public health systems.

Methods: We used longitudinal observations from the National Longitudinal Survey of Public Health Systems to examine how hospital contributions to the delivery of core public health activities varied in 1998, 2006, and 2012. We then used multivariate regression to assess the relationship between the level of hospital contributions and the overall availability of public health activities in the system.

Optical characterization of In-flushed InAs/GaAs quantum dots emitting a broadband spectrum with multiple peaks at ~1 μm.

We investigated optical properties of In-flushed InAs quantum dots (QDs) grown on a GaAs substrate by molecular beam epitaxy. By using the In-flush technique for setting the height of self-assembled InAs QDs, we have tuned the emission wavelength of InAs QDs to the ~1 μm regime, which can be utilized as a non-invasive and deeply penetrative probe for biological and medical imaging systems. The controlled emission exhibited a broadband spectrum comprising multiple peaks with an interval of approximately 30 meV.

Economic shocks and public health protections in US metropolitan areas.

Objectives: We examined public health system responses to economic shocks using longitudinal observations of public health activities implemented in US metropolitan areas from 1998 to 2012.

Methods: The National Longitudinal Survey of Public Health Systems collected data on the implementation of 20 core public health activities in a nationally representative cohort of 280 metropolitan areas in 1998, 2006, and 2012. We used generalized estimating equations to estimate how local economic shocks relate to the scope of activities implemented in communities, the mix of organizations performing them, and perceptions of the effectiveness of activities.

Public health research implementation and translation: evidence from practice-based research networks.

Background: Research on how best to deliver efficacious public health strategies in heterogeneous community and organizational contexts remains limited. Such studies require the active engagement of public health practice settings in the design, implementation, and translation of research. Practice-based research networks (PBRNs) provide mechanisms for research engagement, but until now they have not been tested in public health settings.

Quantum dot selective area intermixing for broadband light sources.

We report a comparison of different capping materials on the intermixing of modulation p-doped InAs/In(Ga)As quantum dots (QD). QD materials with different caps are shown to exhibit significant difference in their optical properties during the annealing process. The selective area intermixing technique is demonstrated to laterally integrate two and three different QD light emitting devices with a single electrical contact.

Expanding delivery system research in public health settings: lessons from practice-based research networks.

Background: Delivery system research to identify how best to organize, finance, and implement health improvement strategies has focused heavily on clinical practice settings, with relatively little attention paid to public health settings-where research is made more difficult by wide heterogeneity in settings and limited sources of existing data and measures. This study examines the approaches used by public health practice-based research networks (PBRNs) to expand delivery system research and evidence-based practice in public health settings.

Methods: Practice-based research networks employ quasi-experimental research designs, natural experiments, and mixed-method analytic techniques to evaluate how community partnerships, economic shocks, and policy changes impact delivery processes in public health settings.

1.55 µm InAs/GaAs quantum dots and high repetition rate quantum dot SESAM mode-locked laser.

High pulse repetition rate (≥ 10 GHz) diode-pumped solid-state lasers, modelocked using semiconductor saturable absorber mirrors (SESAMs) are emerging as an enabling technology for high data rate coherent communication systems owing to their low noise and pulse-to-pulse optical phase-coherence. Quantum dot (QD) based SESAMs offer potential advantages to such laser systems in terms of reduced saturation fluence, broader bandwidth, and wavelength flexibility. Here, we describe the development of an epitaxial process for the realization of high optical quality 1.

Emergence of suspected type D botulism in ruminants in England and Wales (2001 to 2009), associated with exposure to broiler litter.

Scanning surveillance by the Veterinary Laboratories Agency revealed the emergence of suspected botulism in ruminants in 2003, presented as flaccid paralysis. From 2003 to 2009, 168 cattle and 19 sheep incidents were recorded, with mortality between 5 and 80 per cent. All sheep incidents and 95 per cent of cattle incidents had proximity to broiler litter.

Effects of intermixing on modulation p-doped quantum dot superluminescent light emitting diodes.

Different capping of quantum dot (QD) materials is known to produce different degrees of intermixing during a post-growth thermal annealing process. We report a study of the effect of different degrees of intermixing on modulation beryllium doped quantum dot superluminescent light emitting diodes (QD-SLEDs). The intermixed QD-SLEDs show high device performance whilst achieving a large central emission wavelength shift of approximately 100nm compared to the as-grown device.

A p-type-doped quantum dot superluminescent LED with broadband and flat-topped emission spectra obtained by post-growth intermixing under a GaAs proximity cap.

Broadband superluminescent light emitting diodes are realized by a post-growth annealing process, on modulation p-doped multiple InAs/InGaAs/GaAs quantum dot layer structures, under a GaAs proximity cap. The device exhibits a large and flat emission with spectral width up to 132 nm at 2 mW. This is mainly attributed to the reduction of the energy separation between the ground state and the excited state, in addition to the optical quality of the intermixed modulation p-doped quantum dot materials being comparable to that of the as-grown sample.

Realization of extremely broadband quantum-dot superluminescent light-emitting diodes by rapid thermal-annealing process.

The first demonstration, to our knowledge, of the creation of ultrabroadband superluminescent light-emitting diodes using multiple quantum-dot layer structure by rapid thermal-annealing process is reported. The device exhibits a 3 dB emission bandwidth of 146 nm centered at 984 nm with cw output power as high as 15 mW at room temperature corresponding to an extremely small coherence length of 6.6 microm.