Abstract:We demonstrate the first temperature driven mechanically reconfigurable photonic metamaterials (RPMs) providing tunability at optical frequencies.OCIS codes: (160.3918) Metamaterials; (230.4685) Optical microelectromechanical devicesHere we introduce the first mechanically reconfigurable photonic metamaterials with tunable transmission and reflection characteristics provided by nanoscale movements of the components of the metamaterial structure. In the past control of electromagnetic response of metamaterials has only been possible in the terahertz part of the spectrum through micro-electro-mechanically activated motion.Using a sophisticated nanofabrication process on a multilayered metal-dielectric membrane we fabricated a two-dimensional array of C-shaped plasmonic resonators (meta-molecules). In our reconfigurable metamaterial alternating rows of the meta-molecules are supported by different gold-silicon nitride layered substrates of nanoscale thickness, see Fig. 1. Through the virtue of differential thermal expansion the mutual position of alternating rows can be controlled by temperature: we observed a substantial and reversible change of the metamaterial's transmission by tuning temperature within a 200K range, see Fig.2.The metamaterial's transmission spectrum shows several transmission resonances in the near infrared, which are sensitive to coupling between the plasmonic resonators and thus the mutual positions of the meta-molecules in neighboring rows, see Fig. 2. It illustrates the transmission change relative to a reference temperature of 270K. At the resonance frequencies the metamaterial transmission decreases by up to 35% when the sample is cooled to 76K. This large temperature-controlled change in the structure's transmission characteristics is reversible by heating the metamaterial back to its initial temperature We discuss possible improvements and limits of the technology and potential applications of mechanically reconfigurable photonic metamaterials.

We perform a study of the effect of the high in-plane electric field on the spin precession and spin dephasing due to the D'yakonov-Perel' mechanism in n-type GaAs (100) quantum wells by constructing and numerically solving the kinetic Bloch equations. We self-consistently include all of the scattering such as electron-phonon, electron-non-magnetic impurity as well as the electronelectron Coulomb scattering in our theory and systematically investigate how the spin precession and spin dephasing are affected by the high electric field under various conditions. The hot-electron distribution functions and the spin correlations are calculated rigorously in our theory. It is found that the D'yakonov-Perel' term in the electric field provides a non-vanishing effective magnetic field that alters the spin precession period. Moreover, spin dephasing is markedly affected by the electric field. The important contribution of the electron-electron scattering to the spin dephasing is also discussed.

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A sensor system for measurement of pressure and shear at the lower limb residuum/socket interface is described. The system comprises of a flexible sensor unit and a data acquisition unit with wireless data transmission capability. Static and dynamic performance of the sensor system was characterised using a mechanical test machine. The static calibration results suggest that the developed sensor system presents high linearity (linearity error ≤3.8%) and resolution (0.9kpa for pressure and 0.2kpa for shear). Dynamic characterisation of the sensor system shows hysteresis error of approximately 15% for pressure and 8% for shear. Subsequently, a pilot amputee walking test was conducted. Three sensors were placed at the residuum/socket interface of a knee disarticulation amputee and simultaneous measurements were obtained during pilot amputee walking test. The pressure and shear peak values as well as their temporal profiles are presented and discussed. * Corresponding Author: Piotr Laszczak, Engineering Materials Research Group, Faculty of Engineering and the Environment, University of Southampton, SO17 1BJ, Southampton, UK; Email, P.Laszczak@soton.ac.uk; Phone, 07513362435 Preprint submitted to Medical Engineering and PhysicsMarch 1, 2016In particular, peak pressure and shear of approximately 58kPa and 27kPa, respectively, were recorded. Their temporal profiles also provide dynamic coupling information at this critical residuum/socket interface. These preliminary amputee test results suggest strong potential of the developed sensor system for exploitation as an assistive technology to facilitate socket design, socket fit and effective monitoring of lower limb residuum health.Abstract word count: 200

Ligand exchange with octylphosphonate enhances PLQY and LED efficiency.