Neil Alford | Imperial College London (original) (raw)

Papers by Neil Alford

ABSTRACT Amplification of light from reporter fluorophores is a promising strategy to further inc... more ABSTRACT Amplification of light from reporter fluorophores is a promising strategy to further increase the sensitivity of fluorescence based biosensing. One such enhancement system is metal induced fluorescence enhancement (MIFE). The enhanced fluorescence intensity due to the pres-ence of metal nanostructures makes it possible to detect much lower levers of proteins tagged with fluorescence molecules. This paper reports work undertaken on the emission enhancement possible from triangular elements in the bow-tie configuration. The results show that emission enhancement is possible over a long distance (∼ 50 nm).

Optics Express, 2012

The optical characteristics of silicon nanowires grown on Si layers on glass have been modeled us... more The optical characteristics of silicon nanowires grown on Si layers on glass have been modeled using the FDTD (Finite Difference Time Domain) technique and compared with experimental results. The wires were grown by the VLS (vapour-liquid-solid) method using Sn catalyst layers and exhibit a conical shape. The resulting measured and modeled absorption, reflectance and transmittance spectra have been investigated as a function of the thickness of the underlying Si layer and the initial catalyst layer, the latter having a strong influence on wire density. High levels of absorption (&amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;amp;gt;90% in the visible wavelength range) and good agreement between the modeling and experiment have been observed when the nanowires have a relatively high density of ~4 wires/µm2. The experimental and modeled results diverge for samples with a lower density of wire growth. The results are discussed along with some implications for solar cell fabrication.

Journal of Superconductivity, 1990

IEE Seminar Microwave Filters and Multiplexers, 2000

British Ceramic Transactions, 2000

Solid-state masers, hitherto only functional at cryogenic temperatures within a magnetic field, h... more Solid-state masers, hitherto only functional at cryogenic temperatures within a magnetic field, have recently been shown to operate at room temperature and in the earth's field. One of the key components in the room-temperature solid-state maser that has been developed is a gain medium where the stimulated emission occurs. Unlike the ruby gain medium in conventional masers, the new gain medium is an organic semiconductor co-crystal produced from pentacene doped p-terphenyl. Its excited triplet sublevels are degenerated without applying any magnetic field. Moreover, the population inversion of the uppermost sublevel is very high, leading to higher photon emission at very low doping concentrations. This thesis describes the optimization of the pentacene doping concentration to provide a maximum gain output while maintaining a long relaxation time. Single crystals of pentacene doped p-terphenyl were grown via Bridgman-Stockbarger method at various concentrations. Physical and elect...

2005 Asia-Pacific Conference on Applied Electromagnetics

Tunable filters are desirable components for modern RF and microwave communication systems. It is... more Tunable filters are desirable components for modern RF and microwave communication systems. It is required that the subsystems be easily integrated, reconfigurable, reproducible and small. Microstrip filters are good candidates for meeting these requirements. These can be made tunable by using ferroelectric interdigital capacitors to couple half wavelength resonators and applying an electrostatic field using a DC voltage. Based on

International Symposium on Antennas and Propagation Society, Merging Technologies for the 90's, 1990

ABSTRACT

Scientific reports, Jan 10, 2017

Design principles of a new class of microwave thin film bulk acoustic resonators with multiband r... more Design principles of a new class of microwave thin film bulk acoustic resonators with multiband resonance frequency switching ability are presented. The theory of the excitation of acoustic eigenmodes in multilayer ferroelectric structures is considered, and the principle of selectivity for resonator with an arbitrary number of ferroelectric layers is formulated. A so called "criterion function" is suggested that allows to determine the conditions for effective excitation at one selected resonance mode with suppression of other modes. The proposed theoretical approach is verifiedusing thepreexisting experimental data published elsewhere. Finally, the possible application of the two ferroelectric layers structures for switchable microwave overtone resonators, binary and quadrature phase-shift keying modulators are discussed. These devices could play a pivotal role in the miniaturization of microwave front-end antenna circuits.

Physics World, 1995

The other day I was discussing magnetic fields in superconductors with a friend of mine, a fellow... more The other day I was discussing magnetic fields in superconductors with a friend of mine, a fellow Scot as it happens. He knows a thing or two about critical currents and magnetic fields in these materials and was pointing out the huge differences in what is perceived to be a high magnetic field. To people working on superconducting quantum interference devices (SQUIDs), a few millitesla is a high field. However, those working on magnets consider 20–30 T to be high. It is therefore important for all of us working in superconductivity to understand exactly what each section of the community means when talking about high or low currents or fields. This book attempts to explain the issues in straightforward terms.