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Zhu W.M.,Nanyang Technological University | Liu A.Q.,Nanyang Technological University | Liu A.Q.,Institute of Microelectronics, Singapore | Bourouina T.,University Paris Est Creteil | And 8 more authors.
Nature Communications | Year: 2012

Dichroic polarizers and waveplates exploiting anisotropic materials have vast applications in displays and numerous optical components, such as filters, beamsplitters and isolators. Artificial anisotropic media were recently suggested for the realization of negative refraction, cloaking, hyperlenses, and controlling luminescence. However, extending these applications into the terahertz domain is hampered by a lack of natural anisotropic media, while artificial metamaterials offer a strong engineered anisotropic response. Here we demonstrate a terahertz metamaterial with anisotropy tunable from positive to negative values. It is based on the Maltese-cross pattern, where anisotropy is induced by breaking the four-fold symmetry of the cross by displacing one of its beams. The symmetry breaking permits the excitation of a Fano mode active for one of the polarization eigenstates controlled by actuators using microelectromechanical systems. The metamaterial offers new opportunities for the development of terahertz variable waveplates, tunable filters and polarimetry. © 2012 Macmillan Publishers Limited.


Brocklesby W.S.,Optoelectronics Research Center | Nilsson J.,Optoelectronics Research Center | Schreiber T.,Fraunhofer Institute for Applied Optics and Precision Engineering | Limpert J.,Fraunhofer Institute for Applied Optics and Precision Engineering | And 8 more authors.
European Physical Journal: Special Topics | Year: 2014

The application of petawatt lasers to scientific and technological problems is advancing rapidly. The usefulness of these applications will depend on being able to produce petawatt pulses at much higher repetition rates than is presently possible. The International Coherent Amplification Network (ICAN) consortium seeks to design high repetition rate petawatt lasers using large scale coherent beam combination of femtosecond pulse amplifiers built from optical fibres. This combination of technologies has the potential to overcome many of the hurdles to high energy, high average power pulsed lasers, opening up applications and meeting societal challenges. © 2014 EDP Sciences and Springer.


Mills B.,Optoelectronics Research Center | Kundys D.,University of Manchester | Farsari M.,IESL FORTH | Mailis S.,Optoelectronics Research Center | Eason R.W.,Optoelectronics Research Center
Applied Physics A: Materials Science and Processing | Year: 2012

Single ultra-short pulses from Gaussian and vortex beams have been used for the fabrication of complex micro-structures via multi-photon polymerization. The complexity of the resultant micro-structures stems from the modification of both transverse intensity and phase profiles of these single pulses to create modulated scaffolds and hollow cylinders. Experimental results are compared to theoretical models, and good agreement is shown. © 2012 Springer-Verlag.


Ou J.Y.,Optoelectronics Research Center | Plum E.,Optoelectronics Research Center | Jiang L.,University of Southampton | Zheludev N.I.,Optoelectronics Research Center
Nano Letters | Year: 2011

We introduce mechanically reconfigurable photonic metamaterials (RPMs) as a flexible platform for realizing metamaterial devices with reversible and large-range tunable characteristics in the optical part of the spectrum. Here we illustrate this concept for a temperature-driven RPM exhibiting reversible relative transmission changes of up to 50%. © 2011 American Chemical Society.


Feng J.,University College of Applied Sciences | Ding M.,Optoelectronics Research Center | Kou J.-L.,University College of Applied Sciences | Xu F.,University College of Applied Sciences | Lu Y.-Q.,University College of Applied Sciences
IEEE Photonics Journal | Year: 2011

An ∼12-μm-long Bragg grating was engraved in an ∼ 5-μ-diameter optical fiber tip by focused ion beam (FIB) milling. An ∼10-dB extinction was achieved at 1570 nm with only 11 indentations. The grating was used for temperature sensing, and it exhibited a temperature sensitivity of ∼22pm/°C. © 2009 IEEE.


Dumitrescu M.,Optoelectronics Research Center | Laakso A.,Optoelectronics Research Center | Viheriala J.,Optoelectronics Research Center | Kamp M.,University of Würzburg | And 2 more authors.
Optical Fiber Communication Conference, OFC 2013 | Year: 2013

Multi-section distributed-feedback lasers with surface gratings have been fabricated, without re-growth, by employing nanoimprint lithography. High-frequency photon-photon resonance was exploited to extend their direct modulation bandwidth beyond the limitations set by the carrier-photon resonance. OFC/NFOEC Technical Digest © 2013 OSA.


Wales D.J.,Optoelectronics Research Center | Wales D.J.,University of Southampton | Parker R.M.,Optoelectronics Research Center | Parker R.M.,University of Southampton | And 6 more authors.
Sensors and Actuators, B: Chemical | Year: 2016

We report an integrated optical Bragg grating detector, fabricated using a direct UV-writing approach, that when coated with a thin-film of a hydrophobic siloxane co-polymer can perform as an all-optically accessed detector for hydrocarbon vapour. Upon exposure to a series of organic solvent vapours, both negative and positive Bragg wavelength shifts of differing magnitudes were measured. This was attributed to a combination of swelling and/or hydrocarbon solvent filling the free volume within the polymer film. A quantitative structural property relationship (QSPR) approach was utilised to create a multiple variable linear regression model, built from parameters that chemically described the hydrocarbons and the intermolecular interactions present between the co-polymer and hydrocarbon molecules. The resulting linear regression model indicated that the degree of swelling of the polysiloxane thin film when exposed to vapours of different hydrocarbons was due to the physico-chemical properties of the hydrocarbons and that this was the main causative factor of the measured Bragg wavelength shifts. Furthermore, this linear regression model allows for the prediction of the Bragg wavelength shift that would be measured upon exposure to vapours of another defined hydrocarbon. This detector is intrinsically safe in flammable environments. It includes on-chip thermal compensation, operates at telecoms wavelengths and has a predictable response to a variety of hydrocarbons making it ideal for detection of flammable hydrocarbon vapours in industrial and domestic processes. © 2016 The Authors. Published by Elsevier B.V.


Olantera L.,CERN | Sigaud C.,CERN | Troska J.,CERN | Vasey F.,CERN | And 5 more authors.
Journal of Instrumentation | Year: 2013

Hollow-Core Photonic-Bandgap Fibres (HC-PBGFs) offer several distinct advantages over conventional fibres, such as low latency and radiation hardness; properties that make HC-PBGFs interesting for the high energy physics community. This contribution presents the results from a gamma irradiation test carried out using a new type of HC-PBGF that combines sufficiently low attenuation over distances that are compatible with high energy physics applications together with a transmission bandwidth that covers the 1550 nm region. The radiation induced attenuation of the HC-PBGF was two orders of magnitude lower than that of a conventional fibre during a 67.5 h exposure to gamma-rays, resulting in a radiation-induced attenuation of only 2.1 dB/km at an accumulated dose of 940 kGy.© CERN 2013.


Jain S.,Optoelectronics Research Center | Rancano V.J.F.,Optoelectronics Research Center | May-Smith T.C.,Optoelectronics Research Center | Petropoulos P.,Optoelectronics Research Center | And 2 more authors.
International Conference on Transparent Optical Networks | Year: 2014

This paper reviews a novel approach of implementing space-division multiplexing (SDM) based on Multi-element Fiber (MEF) technology. The MEF geometry provides for ultra-low crosstalk between the spatial channels while full compatibility with standard WDM components is maintained. Passive Ge-doped 3-MEFs have been fabricated and characterized and error free WDM data transfer at an aggregate rate of 1014 Gbit/s shown. Also, an Er/Yb-doped cladding-pumped 5-MEF has been demonstrated which enables pump sharing between the signal fiber-elements thereby reducing the number of components in the system. Both these passive and active MEFs have been used to demonstrate an error free SDM system with in-line amplification. © 2014 IEEE.


Mills B.,Optoelectronics Research Center | Feinaeugle M.,Optoelectronics Research Center | Sones C.L.,Optoelectronics Research Center | Rizvi N.,Laser Micromachining Ltd | Eason R.W.,Optoelectronics Research Center
Journal of Micromechanics and Microengineering | Year: 2013

Commercial digital multimirror devices offer a cheap and effective alternative to more expensive spatial light modulators for ablation via beam shaping. Here we present femtosecond laser ablation using the digital multimirror device from an Acer C20 Pico Digital Light Projector and show ablation of complex features with feature sizes ranging from sub-wavelength (400 nm) up to ∼30 ̈m. Simulations are presented that have been used to optimize and understand the experimentally observed resolution. © 2013 IOP Publishing Ltd.

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