Direct optical observation of walls and disclination effects in active photonic devices

Liquid crystal tunable Bragg Gratings defined in planar substrates via a laser patterning technique exhibit complex wavelength tuning. This tuning displays threshold points and hysteresis. These tuning features are shown to be a manifestation of physical processes occurring in the confined geometry of our tunable devices. Such physical processes include the formation and removal of line disclinations and an associated wall. We discuss the effect of walls in the liquid crystal with regards to voltage tuning characteristics and whether they may allow faster wavelength tuning

A two-way photonic interface for linking Sr+ transition at 422 nm to the telecommunications C-band

We report a single-stage bi-directional interface capable of linking Sr+ trapped ion qubits in a long-distance quantum network. Our interface converts photons between the Sr+ emission wavelength at 422 nm and the telecoms C-band to enable low-loss transmission over optical fiber. We have achieved both up- and down-conversion at the single photon level with efficiencies of 9.4% and 1.1% respectively. Furthermore we demonstrate noise levels that are low enough to allow for genuine quantum operation in the future.Comment: 5 pages, 4 figure

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

The response of agricultural prices to a change of the New Zealand exchange rate

The objective of this thesis is to establish the response of agricultural prices to changes of the New Zealand exchange rate. Following an outline of the theory of exchange rate changes a brief history of the use of exchange rate policy in New Zealand is given. A general a priori case of the response of agricultural prices to a change of the exchange rate is established. The general case is examined by way of an analysis of the price setting mechanisms and price movements of wool, lamb and beef. A comparison of the actual and hypothesized price responses indicates that the full price effect of a New Zealand exchange rate change is not always reflected in a change of the domestic price of agricultural products

Managing adaptation: linking theory and practice

Eight years have passed since UKCIP’s Risk and Uncertainty in Decision-making Framework was published. In the intervening years, the risk framework has proved highly influential within the UK and international impacts and adaptation communities, forming the methodological basis of the first ever National Climate Change Risk Assessment in the UK (CCRA) and being reflected in the work of the Intergovernmental Panel on Climate Change (IPCC), Stern Review, Australian Greenhouse Office and others. In that time the adaptation agenda has also become increasingly prominent and the rate of development in adaptation thinking has increased rapidly. Risk based approaches to climate adaptation are now widely embraced in the UK and abroad, making UKCIP’s Risk Framework more relevant than ever. In order to realise its full potential as a decision support tool there is a need to reflect on, and to incorporate, UKCIP’s experience in applying the framework since 2003. In particular, we recognise a need to provide organisations with better guidance on how to initiate their assessments in a way that will enable them to go beyond raising awareness, to undertaking assessments that will lead to the implementation of practical adaptation actions and decisions. This guidance aims to address that need by discussing key issues that should be considered when making the transition from awareness to action. It is aimed specifically at those undertaking a systematic climate change risk based assessment as part of an adaptation work programme and emphasises, in particular, the importance of the scoping phase of assessment. We have found that some of the most important and difficult decisions and judgements in adaptation planning are made during the scoping phase, and that these can profoundly influence the depth and breadth of an assessment and the mechanisms and players involved in subsequent work. If this process is not actively and explicitly engaged with, tacit assumptions can be inadvertently made which strongly influence the outcomes, or create path dependency which limits the flexibility of adaptive planning. This document can be read as a stand-alone piece, or in conjunction with Stages 1 and 2 of UKCIP’s Risk Framework.</p

100 GHz electrically tunable planar Bragg gratings via liquid crystal overlay

We demonstrate 114GHz electrically tunable liquid crystal Bragg gratings using 170Vpp voltage. The devices were made using direct UV grating writing and use evanescent coupling into an electrically tuned nematic liquid crystal. Reconfigurable integrated optical devices are essential in today's dense and complex telecommunication meshes. A commonly employed component on the silica platform fulfilling the above role is a planar Bragg grating. The ability to tune the reflection peak of these gratings is one of the key enablers in realizing an all optical dynamic network. To date, little has been reported on electrically tunable planar Bragg gratings given their potentially superior response times over temperature tuned devices. 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. One route to achieve this is by overlaying the grating with a liquid crystal as many liquid crystals display refractive index anisotropy that can be electrically manipulated. Modifying the liquid crystal refractive index subsequently alters the effective index of the waveguide, leading to Bragg wavelength shift. Using this approach, Sparrow et al [1] have previously demonstrated 35GHz tunability at 1560nm using 80Vpp (peak-to-peak) square-wave with 250mm-spaced aluminium electrodes. Here, we report a maximum tunability of 114GHz at 1561.8nm using patterned ITO glass electrodes with 170Vpp voltage at 1kHz. Two distinct threshold behaviors which manifest only during the increase of supply voltage were also observed

Liquid crystal based tunable WDM planar Bragg grating devices based on precision sawn groove substrates

Current optical telecommunication systems employ dense Wavelength Division Multiplexing (WDM) techniques to increase the data carrying capacity of fiber networks. Dynamic add/drop and filtering processes are crucial for the precise control of individual channels on these networks. Reconfigurable integrated optical devices, such as planar Bragg gratings, can tune the reflection wavelength over several standard channel spacings, providing the possibility for all-optical dynamic networks. Planar devices have the potential to address and tune several channels simultaneously, and have greater potential for integration than fiber equivalents

First order phase change detection using planar waveguide Bragg grating refractometer

Solid-to-liquid and gas-to-liquid phase changes in water and ordered-to-isotropic phase changes in a nematic liquid crystal are detected with an optical sensor. A planar Bragg grating defined purely by refractive index modulation is covered with a water or liquid crystal overcladding and the temperature is controlled to trigger phase changes. Measurement of the Bragg wavelength allows changes of effective refractive index to be detected and discontinuities in behaviour caused by phase transitions can be clearly identified

Integrated Bragg grating sensor applied to detection of phase transitions in liquid crystal and water

A planar Bragg grating in silica is used to form an integrated optical refractive index sensor. The device, inherently suited to remote sensing using single mode transmission fibre, is shown to clearly detect phase transitions in a nematic liquid crystal and in water. Transitions from ordered to isotropic, gas to liquid and liquid to solid as well as the reverse transitions can all be clearly identified. The sensor also allows supercooled liquid to be easily identified, a task previously found challenging by other sensor technologies