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News: Fri 21 June, Kiesinger threat on Berlin, Mon 17 June, Mon 24 June, Aug.24-Sept.7 Sat 24 Aug, Events for children, Variety in Ulster, Tues 9 July, ...
1968 - Gale Group | TDA
Jacqueline Hewett, Valerie Nadeau, James Ferguson, Harry Moseley, Sally H. Ibbotson, John W. Allen, Wilson Sibbett, Miles J. Padgett,
... Andrews, UKSearch for more papers by this authorWilson Sibbett, Wilson Sibbett School of Physics and Astronomy, University of ... Andrews, UKSearch for more papers by this authorWilson Sibbett, Wilson Sibbett School of Physics and Astronomy, University of St. ...
Tópico(s): Photoacoustic and Ultrasonic Imaging
2001 - Wiley | Photochemistry and Photobiology
FROM OUR PARLIAMENTARY CORRESPONDENT, FROM OUR CITY EDITOR, FROM OUR AIR CORRESPONDENT, FROM OUR HOME DEPARTMENT REPORTER, FROM OUR EUROPEAN ECONOMIC CORRESPONDENT, FROM OUR LABOUR CORRESPONDENT, FROM OUR RACING CORRESPONDENT, FROM A SKATING CORRESPONDENT, FROM OUR GOLF CORRESPONDENT, FROM A WOMEN'S HOCKEY CORRESPONDENT, FROM OUR SCHOOLS RUGBY CORRESPONDENT, FROM A RACKETS CORRESPONDENT, FROM OUR MEDICAL CORRESPONDENT, FROM A STAFF REPORTER, FROM MONITOR, FROM OUR UNITED NATIONS CORRESPONDENT, FROM OUR OWN CORRESPONDENT, FROM OUR CORRESPONDENT, FROM OUR OWN CORRESPONDENT., FROM OUR POLITICAL CORRESPONDENT, FROM OUR SPECIAL CORRESPONDENT, FROM OUR SALE ROOM CORRESPONDENT, FROM OUR BOXING CORRESPONDENT, FROM OUR CHURCHES CORRESPONDENT, FROM OUR MIDLAND CORRESPONDENT, MERFYN TURNER. 24 Harberton Road, N.19., CYRIL BIBBY. 246 Cottingham Road, Hull, Nov. 23., R. V. ALLEN., GEORGE H. GORMAN, General Secretary, Friends Home Service Committee. Friends House, Euston Road, N.W.1., A. H. WESTWOOD, Assay Master. Newhall Street, Birmingham 3., MAURICE PARSONAGE Chairman, BERNARD SHERIDAN. 14 Red Lion Square, W.C.1. Nov. 23., A. CHADWICK, Imperial Father, The Times Federated House Chapel. R. GOODANEW, Chairman. S. T. JACKSON, Secretary. The Times, Printing House Square, E.C.4. Nov. 24., ROBERT AUTY. Brasenose College, Oxford, Nov. 23., R. K. S. WOOD. Pyrford Woods, Pyrford, Surrey., Tony Barrett, , From Our Drama Critic, From Our Television Critic, FROM OUR MUSIC CRITIC, By Our City Editor, BY OUR CITY STAFF, from a special correspondent, R. G. Hamilton, R. M. Sibbett, William Warren, from our special correspondent,
... your customer, France Ready To Talk With Mr. Wilson, Explosives danger in Italian floods. News in Brief. ...
1966 - Gale Group | TDA
G. S. Sokolovskiĭ, Vasileia Melissinaki, Ksenia A. Fedorova, V. V. Dudelev, S. N. Losev, V.E. Bougrov, Wilson Sibbett, Maria Farsari, Edik U. Rafailov,
Multimode high-power laser diodes suffer from inefficient beam focusing, leading to a focal spot 10-100 times greater than the diffraction limit. This inevitably restricts their wider use in 'direct-diode' applications in materials processing and biomedical photonics. We report here a 'super-focusing' characteristic for laser diodes, where the exploitation of self-interference of modes enables a significant reduction of the focal spot size. This is achieved by employing a conical microlens fabricated ...
Tópico(s): Optical Coherence Tomography Applications
2018 - Nature Portfolio | Scientific Reports
D.P. Shepherd, Amol Choudhary, A.A. Lagatsky, Pradeesh Kannan, Stephen J. Beecher, R.W. Eason, J. I. Mackenzie, Xian Feng, Wilson Sibbett, C. T. A. Brown,
We report on progress in the field of integrated mode-locked waveguide lasers with an emphasis on compact monolithic designs producing picosecond and femtosecond optical pulses at multi-GHz repetition rates.
Tópico(s): Laser-Matter Interactions and Applications
2015 - IEEE Photonics Society | IEEE Journal of Selected Topics in Quantum Electronics
A.A. Lagatsky, Amol Choudhary, Pradeesh Kannan, D.P. Shepherd, Wilson Sibbett, C. T. A. Brown,
We demonstrate passively mode-locked Yb 3+ -doped glass waveguide lasers in a quasi-monolithic configuration with a maximum pulse repetition frequency up to 15.2 GHz.A semiconductor saturable absorber mirror (SESAM) is used to achieve stable mode-locking around 1050 nm with pulse durations as short as 811 fs and an average power up to 27 mW.Different waveguide samples are also employed to deliver pulses with repetition rates of 4.9 GHz, 10.4 GHz and 12 GHz with an average power of 32 mW, 60 mW and ...
Tópico(s): Laser-Matter Interactions and Applications
2013 - Optica Publishing Group | Optics Express
P. Ashok, Mario Giardini, Kishan Dholakia, Wilson Sibbett,
Abstract We report the development of a fiber‐based Raman sensor to be used in tumour margin identification during endoluminal robotic surgery. Although this is a generic platform, the sensor we describe was adapted for the ARAKNES (Array of Robots Augmenting the KiNematics of Endoluminal Surgery) robotic platform. On such a platform, the Raman sensor is intended to identify ambiguous tissue margins during robot‐assisted surgeries. To maintain sterility of the probe during surgical intervention, ...
Tópico(s): Advanced X-ray and CT Imaging
2013 - Wiley | Journal of Biophotonics
A.A. Lagatsky, O.L. Antipov, Wilson Sibbett,
Femtosecond mode locking of a Tm-doped Lu 2 O 3 ceramic laser is reported.Transform-limited pulses as short as 180 fs are generated at 2076 nm with an average output power of 400 mW and a pulse repetition frequency of 121.2 MHz.An output power up to 750 mW can be reached at the somewhat longer pulse duration of 382 fs.Femtosecond pulse generation is realized in the 2030-2100 nm spectral range.Passive mode locking was achieved using an ion-implanted InGaAsSb quantum-wellbased SESAM.
Tópico(s): Laser-Matter Interactions and Applications
2012 - Optica Publishing Group | Optics Express
Nicola Coluccelli, A.A. Lagatsky, A. Di Lieto, Mauro Tonelli, G. Galzerano, Wilson Sibbett, P. Laporta,
We demonstrate the passive mode-locking operation of an in-band-pumped Ho:YLiF(4) laser at 2.06 μm using a semiconductor saturable absorber mirror based on InGaAsSb quantum wells. A transform-limited pulse train with minimum duration of 1.1 ps and average power of 0.58 W has been obtained at a repetition frequency of 122 MHz. A maximum output power of 1.7 W has been generated with a corresponding pulse duration of 1.9 ps.
Tópico(s): Photorefractive and Nonlinear Optics
2011 - Optica Publishing Group | Optics Letters
Chengli Song, Virginia Appleyard, Karen Murray, Tim Frank, Wilson Sibbett, A. Cuschieri, Alastair M. Thompson,
Abstract In human breast tumors, a 1–2°C increase in skin surface temperature is usually observed at the periphery; it has been proposed that this change is due to the hypervascularity and increased blood flow resulting from tumor‐associated angiogenesis. Here we tested the hypothesis that thermal imaging might represent a useful adjunctive technique in monitoring the growth dynamics of human tumor xenografts. Xenografts were established in immunocomprised nude mice using MDA‐MB‐231 or MCF7 breast ...
Tópico(s): Thermoregulation and physiological responses
2007 - Wiley | International Journal of Cancer
Lynn Paterson, Eirini Papagiakoumou, Graham Milne, V. Garcés‐Chávez, Tina Briscoe, Wilson Sibbett, Kishan Dholakia, Andrew Riches,
A passive, optical cell sorter is created using the light pattern of a 'nondiffracting' beam—the Bessel beam. As a precursor to cell sorting studies, microspheres are used to test the resolution of the sorter on the basis of particle size and refractive index. Variations in size and, more noticeably, refractive index, lead to a marked difference in the migration time of spheres in the Bessel beam. Intrinsic differences (size, refractive index) between native (unlabeled) cell populations are utilized ...
Tópico(s): Laser-Matter Interactions and Applications
2007 - SPIE | Journal of Biomedical Optics
Solomon M. Saltiel, Kaloian Koynov, B. Agate, Wilson Sibbett,
We present a theoretical model that describes the focusing conditions for second-harmonic generation (SHG) of focused femtosecond pulses as a function of group-velocity mismatch (GVM), with direct application to efficient SHG using a "thick" nonlinear crystal. We observe a direct dependence of the optimal focusing ratio, L/b, on the strength of group-velocity mismatch. Our model also describes the temporal duration of the second-harmonic pulses under these conditions as well as the change in optimal ...
Tópico(s): Advanced Fiber Laser Technologies
2004 - Optica Publishing Group | Journal of the Optical Society of America B
Yuri Saveliev, Wilson Sibbett, David M. Parkes,
Distributions of emission centers (ECs) on planar explosive emission dielectric (velvet) cathodes at moderate electric fields of 30–70 kV/cm and pulse durations of ∼2 μs with the use of a fast framing camera have been investigated. The experimental results suggest a link between the EC distribution and current conduction paths through which the electron current is supplied to the cathode plasma. On bare velvet, the surrounding metal electrode was shown not to be of primary importance for the current ...
Tópico(s): Gyrotron and Vacuum Electronics Research
2003 - American Institute of Physics | Journal of Applied Physics
Svetlana A. Tatarkova, Wilson Sibbett, Kishan Dholakia,
Experimental observations of the fluctuation-driven net transport of silica microspheres are presented in a two-dimensional optical potential of circular symmetry created by a Bessel light beam. The optical field is tailored to break symmetry and create a static tilted periodic (washboard) potential. As the tilt of potential exceeds a threshold, a transition between locked and running modes is observed. The running mode manifests itself by the rapid accumulation of particles at the beam center.
Tópico(s): Spectroscopy and Quantum Chemical Studies
2003 - American Physical Society | Physical Review Letters
Yuri Saveliev, Wilson Sibbett, David M. Parkes,
Planar explosive emission diodes operating at moderate pulse energy densities of a few joules per square centimeter conform normally with the Child–Langmuir law in its basic unipolar form. Several recent publications [D. A. Shiffler et al., IEEE Trans. Plasma Sci., 30, 1232, (2002)] suggest, however, that the bipolar flow develops in the diode at comparatively low electron current densities of ∼10 A/cm2 and pulse durations of ∼50 ns. Understanding the nature of a charged particle flow (unipolar or bipolar) ...
Tópico(s): Electrostatic Discharge in Electronics
2003 - American Institute of Physics | Journal of Applied Physics
Yuri Saveliev, Wilson Sibbett, David M. Parkes,
Perveance of a planar diode with explosive emission velvet cathodes of 20–100 mm diameters in a range of diode gaps of 0.5–5 cm is investigated experimentally. An empirical universal curve linking the diode perveance and the cathode radius-to-diode gap ratio is determined thus allowing application of a Child–Langmuir model to diodes of finite dimensions. Comparison of experimental results with two-dimensional (2D) computational models is made and a simple method to translate 2D simulation results ...
Tópico(s): Electromagnetic Simulation and Numerical Methods
2002 - American Institute of Physics | Applied Physics Letters
Jacqueline Hewett, Valerie Nadeau, James Ferguson, Harry Moseley, Sally H. Ibbotson, John W. Allen, Wilson Sibbett, Miles J. Padgett,
A novel, compact and low-cost multispectral fluorescence imaging system with an integrated excitation light source is described. Data are presented demonstrating the application of this method to in vivo monitoring of fluorescence before, during and after topical 5-aminolevulinic acid photodynamic therapy of superficial skin cancers. The excitation source comprised a fluorescent tube with the phosphor selected to emit broadband violet light centered at 394 nm. The camera system simultaneously captured ...
Tópico(s): Ocular Infections and Treatments
2001 - Wiley | Photochemistry and Photobiology
Pablo Loza‐Álvarez, M. Ebrahim-Zadeh, Wilson Sibbett, Derryck T. Reid, David Artigas, M. Missey,
We present detailed experimental results of simultaneous frequency doubling and pulse compression of chirped pulses from a femtosecond optical parametric oscillator using a second-harmonic crystal of aperiodically poled lithium niobate comprising eight different linearly chirped gratings. Our results are compared with a numerical model that incorporates the complex amplitude of the input pulse determined with frequency-resolved optical gating. We use the results of this model to analyze and discuss ...
Tópico(s): Solid State Laser Technologies
2001 - Optica Publishing Group | Journal of the Optical Society of America B
J. Paul Lesso, A. J. Duncan, Wilson Sibbett, Miles J. Padgett,
We incorporate an algorithm for ray tracing in birefringent media into a full ray-tracing package based on the Mathematica software application. To validate the package, we compare the calculated and observed wave-front aberration introduced by an optical system that comprises lenses fabricated from birefringent material. Using the package, we calculate the influence of the lens shape factor on the aberrations associated with the e-ray polarization and show that it differs significantly from that ...
Tópico(s): Optical Polarization and Ellipsometry
2000 - Optica Publishing Group | Applied Optics
John‐Mark Hopkins, Wilson Sibbett,
Tópico(s): Laser-Matter Interactions and Applications
2000 - Springer Nature | Scientific American
Jacqueline Hewett, Tracy McKechnie, Wilson Sibbett, James Ferguson, Colin Clark, Miles J. Padgett,
Abstract Abstract We present a simple fluorescent diagnosis system for the demarcation of skin cancers. 5-aminolaevulinic acid (ALA) cream is applied to the suspicious area resulting in the accumulation of the photosensitizer Protoporphyrin IX (PpIX) in the cancerous tissue. When excited at 400 nm using a filtered mercury arc lamp, the PpIX fluoresces at 635 nm. Our imaging system acquires four spectrally specific images at 635, 540, 470 and 400 nm for the PpIX fluorescence, natural skin autofluorescence ...
Tópico(s): Nonmelanoma Skin Cancer Studies
2000 - Taylor & Francis | Journal of Modern Optics
John‐Mark Hopkins, Wilson Sibbett,
Tópico(s): Advanced Fiber Laser Technologies
2000 - Springer Nature | Scientific American
A. C. Walker, Tsung-Yi Yang, J. Gourlay, J.A.B. Dines, M.G. Forbes, Simon M. Prince, Douglas A. Baillie, David T. Neilson, Rhys Williams, L. C. Wilkinson, George R. Smith, Marc P. Y. Desmulliez, Gerald S. Buller, Mohammad R. Taghizadeh, Andrew J. Waddie, Ian Underwood, C.R. Stanley, F. Pottier, Brigitte Vögele, Wilson Sibbett,
Free-space optical interconnects have been identified as a potentially important technology for future massively parallel-computing systems. The development of optoelectronic smart pixels based on InGaAs/AlGaAs multiple-quantum-well modulators and detectors flip-chip solder-bump bonded onto complementary-metal-oxide-semiconductor (CMOS) circuits and the design and construction of an experimental processor in which the devices are linked by free-space optical interconnects are described. For demonstrating ...
Tópico(s): Semiconductor Quantum Structures and Devices
1998 - Optica Publishing Group | Applied Optics
Dominic E. Withers, Gordon Robertson, Angus Henderson, Yan Tang, Yong Cui, Wilson Sibbett, Bruce Sinclair, Malcolm H. Dunn,
We compare the relative merits of the new nonlinear materials β-barium borate and lithium triborate for use as gain media in singly resonant pulsed optical parametric oscillators pumped by either excimer lasers or frequency-upconverted diode-laser-pumped solid-state lasers. Lithium triborate is the material of choice when one requires low-pump-energy threshold devices (<3 mJ), as in the case of miniature all-solid-state systems based on diode-laser-pumped solid-state lasers, whereas β-barium borate ...
Tópico(s): Advanced Fiber Laser Technologies
1993 - Optica Publishing Group | Journal of the Optical Society of America B
Yong Cui, Dominic E. Withers, Cameron F. Rae, Callum J. Norrie, Yan Tang, Bruce Sinclair, Wilson Sibbett, Malcolm H. Dunn,
An all-solid-state optical parametric oscillator (OPO) has been developed in which the signal and idler waves can be tuned over the ranges 455-665 and 760-1620 nm, respectively, with the potential for covering the entire range 420-2300 nm. The OPO uses a critical type I phase-matching geometry in lithium triborate and is pumped at 355 nm by frequency-tripled radiation from a diode-laser-pumped Nd:YAG laser. Oscillation thresholds (minimum 0.3 mJ), pump depletions (>35%), and linewidths of the OPO are ...
Tópico(s): Advanced Fiber Laser Technologies
1993 - Optica Publishing Group | Optics Letters
Mikio Yamashita, Wilson Sibbett, D. Welford, D. J. Bradley,
An internally frequency-doubled and synchronously mode-locked dye laser has been operated. The average power ∼0.13 mW of the second-harmonic wave with a pulse duration of ∼3 ps has been generated from a thin ADP crystal under pumping by the average power ∼800 mW of a mode-locked Ar ion laser. The effect of intracavity second-harmonic generation on the pulse duration of the fundamental wave is discussed.
Tópico(s): Photorefractive and Nonlinear Optics
1980 - American Institute of Physics | Journal of Applied Physics
A. E. Carruthers, T.K. Lake, Anjali Shah, John W. Allen, Wilson Sibbett, Kishan Dholakia,
Tópico(s): Advanced Fiber Laser Technologies
2005 - Elsevier BV | Optics Communications
Darren Steers, Wilson Sibbett, Miles J. Padgett,
A fiber-coupled, compact laser wavemeter based on a modified Wollaston prism has been constructed and evaluated. The path difference between orthogonal polarization states of the input light varies smoothly across the aperture of the prism forming an interferogram in the spatial domain that is recorded with a CCD detector array. A Fourier transform of this interferogram gives the spectral distribution of the incident light. Alternatively, for a narrow-linewidth source a fringe period measurement ...
Tópico(s): Advanced Fiber Optic Sensors
1998 - Optica Publishing Group | Applied Optics
Junhua Hong, Bruce Sinclair, Wilson Sibbett, Malcolm H. Dunn,
A Q-switched 946-nm Neodymium:yttrium aluminum garnet (Nd:YAG) laser pumped by a diode-laser array has been developed. At room temperature, pulses with 4.9-microj energy and 68.5-ns pulse duration were observed. When the temperature of the Nd:YAG crystal was lowered to 5 degrees C, the duration of the pulses was reduced to 62 ns, giving rise to peak powers of 76 W. By focusing the Q-switched pulses into a 5-mm-long potassium niobate crystal, second-harmonic generation produced blue light pulses at ...
Tópico(s): Advanced Fiber Laser Technologies
1992 - Optica Publishing Group | Applied Optics
Valerie Nadeau, Khaled Hamdan, Jacqueline Hewett, Wilson Sibbett, Iain S. Tait, A. Cuschieri, Miles J. Padgett,
We describe a combined endoscopic fluorescence imaging and spectroscopy system for the detection of gastro-intestinal cancers, utilizing the fluorescence from aminolaevulinic acid-induced protoporphyrin IX. Both the imaging and spectroscopy systems are controlled by a single desktop PC, which also carries out image processing and stores spectral data, enabling real-time display of images and spectra on one monitor. These systems have been tested in vivo and the results illustrate the potential of ...
Tópico(s): Cancer Research and Treatments
2002 - Taylor & Francis | Journal of Modern Optics