Manufacturing high purity chalcogenide glass

Chalcogenide materials are finding increasing interest as an active material in next generation optical and electronic devices. There wide range of properties, ranging from photosensitivity, ability to host rare earth ions, electrical conductivity, phase change, exceptional optical non-linearity's to name only a few are fueling this interest. Moreover, the ability to synthesize these materials in numerous forms as diverse as 2D monolayers, microspheres, optical fibres, nanowires, thin films as well as bulk glass ingots of over a kilogram in size ensures their application space is vast.We began preparation of chalcogenides, largely based on sulphides, in 1992 and since then have built up an extensive capability for their purification, synthesis and fabrication in various forms. A key aspect of this facility is the ability to process in a flowing atmosphere of hydrogen sulphide which provided the capability of synthesis from elemental, oxide or halide precursors, processing through various chemical vapour deposition reactions as well as post purification. In this talk we describe the range of materials we synthesize highlighting high purity sulphide bulk glass and transition metal di-chalcogenides for electronic applications, crystalline semiconductors for solar cell applications, low power phase change memory devices, switchable metamaterial devices as well as traditional chalcogenides glass and optical fibre

Ion-implanted lanthanum fluoride waveguides

The effects of He+ and H+ implantation into LaF3 substrates have been investigated at both room temperature and 77 K. At room temperature the surface of the samples becomes black, possibly due to chemical reduction effects, but at low temperature the crystals remain clear and a refractive index change is observed which produces a surface waveguide. The dark mode spectra of these guides have been recorded using the prism coupling technique, and their refractive index profiles have been deduced from the spacing of these modes. The ion implantation produces a thin optical barrier layer of low refractive index at the end of the ion range. This paper discusses the use of multiple-energy implantation to produce a broad optical barrier in order to reduce the tunnelling losses of the guides, and subsequent thermal annealing to reduce absorption and scattering losses caused by colour centre formation in the electronic stopping surface region of the guides. It is concluded that either single- or multiple-energy He+ implants can be ideally used to form waveguides, for applications in the blue/UV or red/IR wavelength regions, respectively, with losses of a few dB/cm

Effects Of Kaluza-Klein Excited W On Single Top Quark Production At Tevatron

In extra dimension theories if the gauge bosons of the standard model propagate in the bulk of the extra dimensions then they will have Kaluza-Klein excitations that can couple to the standard model fermions. In this paper we study the effects of the first excited Kaluza-Klein mode of the W on single top production at the Tevatron. We find that the cross section for the single top production can be significantly reduced if the mass of the first Kaluza-Klein excited $W \sim 1$ TeV. Hence, a measurement of the single top production cross section smaller than the standard model prediction would not necessarily imply $V_{tb} <1$ or evidence of extra generation(s) of fermions mixed with the third generation.Comment: Text added, Latex, 16 pages, 3 figures, To appear in Phys. Lett.

Ion beam manipulation of the photorefractive properties of SBN planar waveguides

Photo refractive planar waveguides have been fabricated in cerium doped Strontium Barium Niobate (SrxBa(1-x)Nb2O6 : SBN) single crystals by ion beam implantation. The losses measured were as low as 0.1 dB /cm and 7.0 dB /cm for the TM and TE modes respectively. Subsequent two beam coupling experiments performed on the waveguides showed that, unlike BaTiO3 and KNbO3 waveguides formed by ion beam implantation, the two-beam coupling gain direction did not reverse. The response time had also been reduced by two orders of magnitude

Consumption strategies and motivations of Chinese consumers: The case of UK sustainable luxury fashion

Purpose: The purpose of this paper is to explore Chinese consumers’ motivations to purchase luxury fashion products in the UK and how far sustainability plays a role in the decision-making process, by extending the consumer typology of translators, exceptors, selectors. The authors further add an additional dimension to defining “luxury”. Design/methodology/approach: An exploratory design utilising multiple qualitative research tools (semi-structured interviews, focus groups) provides the basis for this research. A grounded analysis was applied. Findings: Findings map motivational drivers to purchasing luxury products and establish a fourth consumer type “indulgers”. Well-being further emerged as a key characteristic that defines “luxury”. Research limitations/implications: The sample size is limited to Chinese consumers purchasing luxury fashion in the UK, and thus may not be generalised. Practical implications: This research helps managers to understand the consumer types and underlying motivations of Chinese consumers purchasing luxury fashion in the UK. As one of the largest target groups, this research informs managers on how to further capitalise on this market. Originality/value: This paper creates a new consumer typology that not only categorises consumers according to their consumption aspects, but further identifies their underlying motivations to do so

Increasing Downlink Cellular Throughput with Limited Network MIMO Coordination

Single-user, multiuser, and network MIMO performance is evaluated for downlink cellular networks with 12 antennas per site, sectorization, universal frequency reuse, scheduled packet-data, and a dense population of stationary users. Compared to a single-user MIMO baseline system with 3 sectors per site, network MIMO coordination is found to increase throughput by a factor of 1.8 with intra-site coordination among antennas belonging to the same cell site. Intra-site coordination performs almost as well as a highly sectorized system with 12 sectors per site. Increasing the coordination cluster size from 1 to 7 sites increases the throughput gain factor to 2.5

Demonstration of a 280-Gbit/s free-space SDM communications link utilizing plane-wave spatial multiplexing

We demonstrate a 280-Gbit/s free-space SDM communications link incorporating a set of independent tilted truncated plane-waves, each generated by a single mode fiber placed at the back-focal plane of a spherical lens. Each of the 7 tilted plane-wave channels are encoded with a 40-Gbit/s 16-QAM signal. Our approach comprises two identical linear fiber-arrays placed approximately 5 m apart. As each fiber array is placed at the back-focal-plane of a spherical lens, each fiber array is effectively placed in a conjugate image plane of the other. A channel crosstalk less than 26 dB is shown, with a bit-error-rate below the FEC threshold of 3.8 × 10−3

On hyperovals of polar spaces

We derive lower and upper bounds for the size of a hyperoval of a finite polar space of rank 3. We give a computer-free proof for the uniqueness, up to isomorphism, of the hyperoval of size 126 of H(5, 4) and prove that the near hexagon E-3 has up to isomorphism a unique full embedding into the dual polar space DH(5, 4)

Intermediate stages of electrochemical oxidation of single-crystalline platinum revealed by in situ Raman spectroscopy

Catalysis and Surface Chemistr

Lepton Polarization and Forward-Backward Asymmetries in b -> s tau+ tau-

We study the spin polarizations of both tau leptons in the decay b -> s tau+ tau-. In addition to the polarization asymmetries involving a single tau, we construct asymmetries for the case where both polarizations are simultaneously measured. We also study forward-backward asymmetries with polarized tau's. We find that a large number of asymmetries are predicted to be large, >~ 10%. This permits the measurement of all Wilson coefficients and the b-quark mass, thus allowing the standard model (SM) to be exhaustively tested. Furthermore, there are many unique signals for the presence of new physics. For example, asymmetries involving triple-product correlations are predicted to be tiny within the SM, O(10^{-2}). Their observation would be a clear signal of new physics.Comment: 21 pages, LaTeX, 4 figures (included). Paper somewhat reorganized, references greatly expanded, conclusions unchange