ZnO random laser diode arrays for stable single-mode operation at high power

2010-2011 > Academic research: refereed > Publication in refereed journalVersion of RecordPublishe

Monolithic semiconductor lasers with dynamically tunable linear-to-circular polarization

The ability to control the polarization state of emission from semiconductor lasers is essential for many applications in spectroscopy, imaging, and communications, inter alia, with monolithic integration approaches being extremely beneficial. Although manipulating the output polarization of radiation from a laser can be achieved through a number of approaches, obtaining continuous dynamic control, e.g., from linear to circular, remains extremely challenging. In this paper, we demonstrate that the polarization of terahertz (THz) frequency radiation can be continuously tuned electronically from linear to circular polarization by monolithically integrating in-plane metasurfaces with two phase-locked semiconductor-based THz quantum cascade lasers. Moreover, the metasurfaces—metal antenna arrays in this case—also act as efficient beam collimators, yielding a collimated beam divergence of ∼10° × 10°. Our results, however, have broad applicability to a wide range of semiconductor lasers operating from the visible to THz regions of the electromagnetic spectrum

Design of dry powder formulations of pH responsive peptide/plasmid DNA complexes for pulmonary delivery

Poster Presentation: no. 13PS50Respiratory diseases are substantial public health problems around the world. Recently, nucleic acid was developed as a potential therapeutic strategy to tackle a series of lung diseases. Delivery still poses one of the major challenges for their clinical application. pH responsive peptides containing either histidine or derivatives of 2,3-diaminopropionic acid (Dap) can mediate effective DNA transfection in lung epithelial cells with the latter remaining effective even in the presence of lung surfactant containing bronchoalveolar fluid (BALF), which make them promising vectors for delivering therapeutic nucleic acid to the airways .....published_or_final_versio

Ultrafast non-inverting wavelength conversion by cross-absorption modulation in silicon wire waveguides.

Abstract We demonstrate all-optical wavelength conversion by means of cross absorption effect induced by Two Photon Absorption (TPA) in submicron sized Si wire waveguides. Optical pulses of 1.6 ps at 1GHz repetition rate were successfully converted from 1550nm to 1532nm. We discuss the performance at higher speed. Our results showed that silicon waveguides have potential applications in high speed photonic signal processing

Profiling biomolecules at cell-biomaterial interface by quantitative proteomics

Session: Controlling Microenvironment and Cell Fate: abstract no. 789INTRODUCTION: Implant surface structure and chemistry determines the contacting cell’s fate. Therefore, the fate of those cells directly affect bone-implant incorporation in clinical practice1-5. However, how these chemical and mechanical signals translating to cellular responses are not yet known. The major drawback is a lack of systematic study of cellbiomaterial interaction in terms of protein expression, specifically, at the attachment interface between the cell and biomaterial (adherence surface, AS). Therefore, we have proposed to unbiasedly identify the biomolecules at the interface by proteomics. This method combines the use of a subcellular fractionation with quantitative mass …postprintThe 2010 North America Conference of the Tissue Engineering and Regenerative Medicine International Society (TERMIS-NA 2010), Orlando, FL., 5-8 December 2010

Designer Multimode Localized Random Lasing in Amorphous Lattices at Terahertz Frequencies

Random lasers are a special class of laser in which light is confined through multiple scattering and interference process in a disordered medium, without a traditional optical cavity. They have been widely studied to investigate fundamental phenomena such as Anderson localization, and for applications such as speckle-free imaging, benefitting from multiple lasing modes. However, achieving controlled localized multi-mode random lasing at long wavelengths, such as in the terahertz (THz) frequency regime, remains a challenge. Here, we study devices consisting of randomly-distributed pillars fabricated from a quantum cascade gain medium, and show that such structures can achieve transversemagnetic polarized (TM) multi-mode random lasing, with strongly localized modes at THz frequencies. The weak short-range order induced by the pillar distribution is sufficient to ensure high quality-factor modes that have a large overlap with the active material. Furthermore, the emission spectrum can be easily tuned by tailoring the scatterer size and filling fraction. These “designer” random lasers, realized using standard photolithography 2 techniques, provide a promising platform for investigating disordered photonics with predesigned randomness in the THz frequency range, and may have potential applications such as speckle-free imaging

Modelling reef hydrodynamics and sediment mobility under sea level rise in atoll reef island systems

This is the author accepted manuscript. The final version is available on open access from Elsevier via the DOI in this record. Low-lying coral reef islands will be significantly impacted by future sea level rise (SLR). It is generally expected that SLR will destabilise reef islands because increasing reef submergence allows larger waves, and therefore greater energy transmission, across reef flats. However, the impact of SLR on altering both reef flat sediment transport and sediment delivery to island shorelines is poorly understood. Here, we use the currents of removal approach (coupling two-dimensional wave modelling with settling velocity data from 186 benthic sediment samples) to model shifts in both reef hydrodynamics and benthic sediment transport under scenarios of mean reef submergence (MRS = +0 m, +0.5 m, +1 m) at two atoll rim reef sites in the Maldives. Under contemporary conditions (MRS = +0 m), we found that benthic sediment transport is likely occurring, consistent with active reef-to-island sediment connectivity. Under conditions of increased MRS, shifts in wave velocities, and in turn sediment potential mobility, were both non-linear and non-uniform. Significant between-site differences were found in the magnitude of projected shifts in sediment mobility under scenarios of increased MRS, which implies that morphological responses to increases in MRS are likely to be diverse, even over local scales. Under increased MRS, the largest increases in sediment mobility were projected on the inner reef flat, whereas lagoonal zones remained as sinks for sediment deposition. We thus hypothesize that while reef islands will persist as sedimentary landforms under projected rates of MRS, lagoonward reef island migration is likely to occur. Findings have implications for predicting the future adaptive capacity of atoll nations. The challenge is to incorporate such potential increases in island mobility and intra-regional diversity in reef system geomorphic responses to sea level rise into national-scale vulnerability assessments.NER

Who died as a result of the tsunami? – Risk factors of mortality among internally displaced persons in Sri Lanka: a retrospective cohort analysis

BACKGROUND: Describing adverse health effects and identifying vulnerable populations during and after a disaster are important aspects of any disaster relief operation. This study aimed to describe the mortality and related risk factors which affected the displaced population over a period of two and a half months after the 2004 Indian Ocean tsunami in an eastern coastal district of Sri Lanka. METHODS: A cross-sectional household survey was conducted in 13 evacuation camps for internally displaced persons (IDP). Information on all pre-tsunami family members was collected from householders, and all deaths which occurred during the recall period (77 to 80 days starting from the day of the tsunami) were recorded. The distribution of mortality and associated risk factors were analysed. Logistic regression modelling using the generalized estimating equations method was applied in multivariate analysis. RESULTS: Overall mortality rate out of 3,533 individuals from 859 households was 12.9% (446 deaths and 11 missing persons). The majority of the deaths occurred during and immediately after the disaster. A higher mortality was observed among females (17.5% vs. 8.2% for males, p < 0.001), children and the elderly (31.8%, 23.7% and 15.3% for children aged less than 5 years, children aged 5 to 9 years and adults over 50 years, respectively, compared with 7.4% for adults aged 20 to 29 years, p < 0.001). Other risk factors, such as being indoors at the time of the tsunami (13.8% vs. 5.9% outdoors, p < 0.001), the house destruction level (4.6%, 5.5% and 14.2% in increasing order of destruction, p < 0.001) and fishing as an occupation (15.4% vs. 11.2% for other occupations, p < 0.001) were also significantly associated with increased mortality. These correlations remained significant after adjusting for the confounding effects by multivariate analysis. CONCLUSION: A significantly high mortality was observed in women and children among the displaced population in the eastern coastal district of Sri Lanka who were examined by us. Reconstruction activities should take into consideration these changes in population structure