Coherence effects in propagation through photonic crystals

We have analytically studied how a partially coherent quasi plane wave is affected by a photonic crystal structure including a grating. The analysis is presented for spatial and temporal cases showing the possibility to determine the coherence characteristics of the pulse.

Absence of Anderson localization in certain random lattices

This is the final version of the article. Available from American Physical Society via the DOI in this record.We report on the transition between an Anderson localized regime and a conductive regime in a one-dimensional microwave scattering system with correlated disorder. We show experimentally that when long-range correlations are introduced, in the form of a power-law spectral density with power larger than 2, the localization length becomes much bigger than the sample size and the transmission peaks typical of an Anderson localized system merge into a pass band. As other forms of long-range correlations are known to have the opposite effect, i.e., to enhance localization, our results show that care is needed when discussing the effects of correlations, as different kinds of long-range correlations can give rise to very different behavior.J.B. acknowledge support from the Leverhulme Trust's Philip Leverhulme Prize. I.R.H. acknowledges financial support from the Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom, via the EPSRC Centre for Doctoral Training in Metamaterials (Grant No. EP/L015331/1)

Stem cells as source for retinal pigment epithelium transplantation

Inherited maculopathies, age related macular degeneration and some forms of retinitis pigmentosa are associated with impaired function or loss of the retinal pigment epithelium (RPE). Among potential treatments, transplantation approaches are particularly promising. The arrangement of RPE cells in a well-defined tissue layer makes the RPE amenable to cell or tissue sheet transplantation. Different cell sources have been suggested for RPE transplantation but the development of a clinical protocol faces several obstacles. The source should provide a sufficient number of cells to at least recover the macula area. Secondly, cells should be plastic enough to be able to integrate in the host tissue. Tissue sheets should be considered as well, but the substrate on which RPE cells are cultured needs to be carefully evaluated. Immunogenicity can also be an obstacle for effective transplantation as well as tumorigenicity of not fully differentiated cells. Finally, ethical concerns may represent drawbacks when embryo-derived cells are proposed for RPE transplantation. Here we discuss different cell sources that became available in recent years and their different properties. We also present data on a new source of human RPE. We provide a protocol for RPE differentiation of retinal stem cells derived from adult ciliary bodies of post-mortem donors. We show molecular characterization of the in vitro differentiated RPE tissue and demonstrate its functionality based on a phagocytosis assay. This new source may provide tissue for allogenic transplantation based on best matches through histocompatibility testing

Phase-change metasurfaces for dyamic beam steering and beam shaping in the infrared

This is the author accepted manuscript. The final version is available from the publisher via the DOI in this recordWe present novel phase-change material based metasurfaces for dynamic, recnofigurable and efficient wavefront shaping in the infrared spectrum. Dynamic control and reconfigurability was obtained by incorporating an ultra-thin layer of the widely-used phase change material Ge2Sb2Te5. Our approach exploits hybrid dielectic/plasmonic resonances to achieve local (subwavelength) phase control of light with low losses. A full 2π optical phase coverage was achieved with this approach, which allows for a wide flexibility in terms of realizable designs. To illustrate this concept, dynamic beam steering devices and reconfigurable planar focusing mirrors (both operating at optical telecommunications wavelengths) and their performance investigated. Absolute efficiencies up to 65% are achieved, significantly higher than the efficiencies of more commonly reported plasmonic-based phase-change metasurfaces.CDW acknowledges funding via the US Naval Research Laboratories ONRG programme (#N62909-16-1-2174) and the EPSRC ChAMP and WAFT grants (EP/M015130/1 and EP/M015173/1). CRdeG acknowledges funding via the EPSRC CDT in Metamaterials (EP/L015331/1). CRdeG Acknowledges Joaquin Faneca-Ruedas and Dr Anna Baldycheva