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ABSTRACT: Non-volatile, bidirectional, all-optical switching in a phase-change metamaterial delivers high-contrast transmission and reflection modulation at near- to mid-infrared wavelengths in device structures down to ≈(1) /27 of a wavelength thick.
Advanced Materials 04/2013; · 13.88 Impact Factor
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ABSTRACT: According to Huygens' superposition principle, light beams traveling in a
linear medium will pass though one another without mutual disturbance. Indeed,
it is widely held that controlling light signals with light requires intense
laser fields to facilitate beam interactions in nonlinear media, where the
superposition principle can be broken. We demonstrate here that two coherent
beams of light of arbitrarily low intensity can interact on a metamaterial
layer of nanoscale thickness in such a way that one beam modulates the
intensity of the other. We show that the interference of beams can eliminate
the plasmonic Joule losses of light energy in the metamaterial or, in contrast,
can lead to almost total absorbtion of light. Applications of this phenomenon
may lie in ultrafast all-optical pulse-recovery devices, coherence filters and
THz-bandwidth light-by-light modulators.
03/2012;
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ABSTRACT: Periodic nanostructuring can enhance the optical nonlinearity of plasmonic metals by several orders of magnitude. By patterning a gold film, the largest sub-100 femtosecond nonlinearity is achieved, which is suitable for terahertz rate all-optical data processing as well as ultrafast optical limiters and saturable absorbers.
Advanced Materials 12/2011; 23(46):5540-4. · 13.88 Impact Factor
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ABSTRACT: In the microwave part of the spectrum, where losses are minimal, metal films regularly patterned (perforated) on the sub-wavelength scale achieve spectral selectivity by balancing the transmission and reflection characteristics of the surface. Here we show for optical frequencies, where joule losses are important, that periodic structuring of a metal film without violation of continuity (i.e. without perforation) is sufficient to achieve substantial modification of reflectivity. By engineering the geometry of the structure imposed on a surface one can dramatically change the perceived color of the metal without employing any form of chemical modification, thin-film coating or diffraction effects. This novel frequency selective effect is underpinned by plasmonic Joule losses in the constituent elements of the patterns (dubbed 'intaglio' and 'bas relief' metamaterials to distinguish indented and raised structures respectively) and is specific to the optical part of the spectrum. It has the advantage of maintaining the integrity of metal surfaces and is well suited to high-throughput fabrication via techniques such as nano-imprint.
Optics Express 11/2011; 19(23):23279-85. · 3.59 Impact Factor
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ABSTRACT: We analyze ultrafast surface plasmon-polariton pulse reshaping effects and nonlinear propagation modes for metal/dielectric plasmon waveguides. It is found that group velocity and loss dispersion effects can substantially modify both pulse duration (broadening/narrowing) and intensity decay (acceleration/retardation) by as much as several tens of percentage points in the short-pulse regime and that metallic nonlinearities alone may support soliton, self-focusing, and self-compressing modes.
Optics Letters 01/2011; 36(2):250-2. · 3.40 Impact Factor
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ABSTRACT: The fabrication of indented ('intaglio') or raised ('bas-relief')
sub-wavelength metamaterial patterns on a metal surface provides a mechanism
for changing and controlling the colour of the metal without employing any form
of chemical surface modification, thin-film coating or diffraction effects. We
show that a broad range of colours can be achieved by varying the structural
parameters of metamaterial designs to tune absorption resonances. This novel
approach to the 'structural colouring' of pure metals offers great versatility
and scalability for both aesthetic (e.g. jewellery design) and functional (e.g.
sensors, optical modulators) applications. We focus here on visible colour but
the concept can equally be applied to the engineering of metallic spectral
response in other electromagnetic domains.
11/2010;
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physica status solidi (RRL) - Rapid Research Letters 08/2010; 4(10):274 - 276. · 2.22 Impact Factor
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Graham R Broder,
Rohan T Ranasinghe,
Joseph K She,
Shahanara Banu,
Sam W Birtwell,
Gabriel Cavalli,
Gerasim S Galitonov,
David Holmes,
Hugo F P Martins, Kevin F Macdonald,
Cameron Neylon,
Nikolay Zheludev,
Peter L Roach,
Hywel Morgan
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ABSTRACT: Microparticles incorporating micrometer-sized diffractive bar codes have been modified with oligonucleotides and immunoglobulin Gs to enable DNA hybridization and immunoassays. The bar codes are manufactured using photolithography of a chemically functional commercial epoxy photoresist (SU-8). When attached by suitable linkers, immobilized probe molecules exhibit high affinity for analytes and fast reaction kinetics, allowing detection of single nucleotide differences in DNA sequences and multiplexed immunoassays in <45 min. Analysis of raw data from assays carried out on the diffractive microparticles indicates that the reproducibility and sensitivity approach those of commercial encoding platforms. Micrometer-sized particles, imprinted with several superimposed diffraction gratings, can encode many million unique codes. The high encoding capacity of this technology along with the applicability of the manufactured bar codes to multiplexed assays will allow accurate measurement of a wide variety of molecular interactions, leading to new opportunities in diverse areas of biotechnology such as genomics, proteomics, high-throughput screening, and medical diagnostics.
Analytical Chemistry 03/2008; 80(6):1902-9. · 5.86 Impact Factor
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ABSTRACT: In a single gallium nanoparticulate, self-assembled (from an atomic beam) in a nanoaperture at the tip of a tapered optical fiber, we have observed reversible light-induced reflectivity changes associated with a sequence of transformations between a number of structural forms with different optical properties, stimulated by optical excitation at nanowatt power levels. The ability to change the optical properties of a nanoparticulate using structural transformations provides a new mechanism for photonic functionality on the nanoscale.
Nano Letters 11/2005; 5(10):2104-7. · 13.20 Impact Factor
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Nat Photon. 3(1):55-58.
