Continuous Ultraviolet to Blue-Green Astrocomb

The characterization of Earth-like exoplanets and precision tests of cosmological models using next-generation telescopes such as the ELT will demand precise calibration of astrophysical spectrographs in the visible region, where stellar absorption lines are most abundant. Astrocombs--lasers providing a broadband sequence of ultra-narrow, drift-free, regularly spaced optical frequencies on a multi-GHz grid--promise an atomically-traceable, versatile calibration scale, but their realization is challenging because of the need for ultra-broadband frequency conversion of mode-locked infrared lasers into the blue-green region. Here, we introduce a new concept achieving a broad, continuous spectrum by combining second-harmonic generation and sum-frequency-mixing in an aperiodically-poled MgO:PPLN waveguide to generate gap-free 390-520 nm light from a 1 GHz Ti:sapphire laser frequency comb. We lock a low-dispersion Fabry-Perot etalon to extract a sub-comb of bandwidth from 392-472 nm with a spacing of 30 GHz, visualizing the thousands of resulting comb modes on a high resolution cross-dispersion spectrograph. Complementary experimental data and simulations demonstrate the effectiveness of the approach for eliminating the spectral gaps present in second-harmonic-only conversion, in which weaker fundamental frequencies are suppressed by the quadratic \{chi}^((2)) nonlinearity. Requiring only ~100 pJ pulse energies, our concept establishes a practical new route to broadband UV-visible generation at GHz repetition rates.Comment: 14 pages; 4 figure

Plan or React? Analysis of Adaptation Costs and Benefits Using Integrated Assessment Models

This report examines adaptation and mitigation within an integrated framework. Global and regional costs of adaptation are assessed dynamically and the resulting benefits are quantified. This is accomplished by developing a framework to incorporate adaptation as a policy variable within three Integrated Assessment Models (IAMs); the global Dynamic Integrated model of Climate and the Economy (DICE), the Regional Integrated model of Climate and the Economy (RICE), and the World Induced Technical Change Hybrid (WITCH) model. The framework developed here takes into account investments in reactive adaptation and in adaptation “stocks”, as well as investments in building adaptive capacity. This report presents the first inter-model comparison of results on adaptation costs using the emerging category of adaptation-IAMs. Results show that least-cost policy response to climate change will need to involve subsantial amounts of mitigation efforts, investments in adaptation stock, reactive adaptation measures and adaptive capacity to limit the remaining damages

Making Brexit Work for the Environment and Livelihoods : Delivering a Stakeholder Informed Vision for Agriculture and Fisheries

1. The UK’s decision to leave the EU has far-reaching, and often shared, implications for agriculture and fisheries. To ensure the future sustainability of UK agricultural and fisheries systems, we argue that it is essential to grasp the opportunity that Brexit is providing to develop integrated policies that improve the management and protection of the natural environments, upon which these industries rely. 2. This article advances a stakeholder informed vision of the future design of UK agriculture and fisheries policies. We assess how currently emerging UK policy will need to be adapted in order to implement this vision. Our starting point is that Brexit provides the opportunity to redesign current unsustainable practices and can, in principle, deliver a sustainable future for agriculture and fisheries. 3. Underpinning policies with an ecosystem approach, explicit inclusion of public goods provision and social welfare equity were found to be key provisions for environmental, agricultural and fishery sustainability. Recognition of the needs of, and innovative practices in, the devolved UK nations is also required as the new policy and regulatory landscape is established. 4. Achieving the proposed vision will necessitate drawing on best practice and creating more coherent and integrated food, environment and rural and coastal economic policies. Our findings demonstrate that “bottom-up” and co-production approaches will be key to the development of more environmentally sustainable agriculture and fisheries policies to underpin prosperous livelihoods. 5. However, delivering this vision will involve overcoming significant challenges. The current uncertainty over the nature and timing of the UK’s Brexit agreement hinders forward planning and investment while diverting attention away from further in-depth consideration of environmental sustainability. In the face of this uncertainty, much of the UK’s new policy on the environment, agriculture and fisheries is therefore ambitious in vision but light on detail. Full commitment to co-production of policy with devolved nations and stakeholders also appears to be lacking, but will be essential for effective policy development and implementation

Towards high-speed liquid crystal electrically tunable planar Bragg gratings for integrated optical networks

Liquid crystal-based integrated optical devices offer the potential for high speed and dynamically tunable optical switches in modern telecommunications networks. Here, electrically tunable devices have major advantages over their thermal counterparts, with superior response times and low operating voltages (~100V). Our approach to achieving such devices is to fabricate planar optical waveguides with integrated Bragg gratings via direct UV writing1 into silica-on-silicon samples with evanescent field coupling into a liquid crystal overlay through an etched window (Fig. 1(a)). Such electrically tunable devices work on the principle of shifting the Bragg wavelength by modifying the effective index of a waveguide in a multilayer substrate. Electrically controlled liquid crystal birefringence modifies the waveguide effective index, producing a Bragg wavelength shift. In our early samples, Merck 18523 nematic liquid crystal is used as it has a compatible refractive index to silica (n=1.49 at lambda=1550nm). Homeotropic alignment of the liquid crystal is provided by application of a surfactant layer

A comparison of model laws as a starting point for the development of an enforceable international consumer protection regime

This article is concerned primarily with an examination and comparison of select aspects of the model international consumer protection laws proposed by the United Nations (UN), the European Union (EU), and the Organisation for Economic Co-operation and Development (OECD), using the Trade Practices Act 1974 (Australia) as a basis for examination and comparison. As a secondary consideration, it also broadly examines the content of, and differences between, the model laws. The motive for this article is that any future enforceable international consumer protection regime (possibly in the form of an international treaty or convention) would need to take into account the UN, EU and OECD guidelines. A cross-comparison of those model laws, and a comparison of them with the consumer protection provisions of a well established national consumer protection law, should provide a useful starting point for the development of such a regime. The 'select aspects' of the model laws in question are the various provisions of those laws which could relate to situations involving the wrong delivery or non-delivery of goods