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Author

David J. Richardson

Bio: David J. Richardson is an academic researcher from University of Southampton. The author has contributed to research in topic(s): Optical fiber & Fiber laser. The author has an hindex of 111, co-authored 1743 publication(s) receiving 53466 citation(s). Previous affiliations of David J. Richardson include University of Sydney & Karlsruhe Institute of Technology.
Papers
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Journal ArticleDOI
01 May 2013-Nature Photonics
Abstract: This Review summarizes the simultaneous transmission of several independent spatial channels of light along optical fibres to expand the data-carrying capacity of optical communications. Recent results achieved in both multicore and multimode optical fibres are documented.

2,125 citations


6


Journal ArticleDOI
TL;DR: This paper reviews the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in Terms of high-power performance.
Abstract: The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

1,510 citations


Journal ArticleDOI
17 May 2004-Optics Express
TL;DR: It is shown that very-long ultra-low-loss tapers can in fact be produced using a conventional fiber taper rig incorporating a simple burner configuration, and the optical losses achieved are one order of magnitude lower than losses previously reported in the literature for tapers of a similar size.
Abstract: Optical fiber tapers with a waist size larger than 1microm are commonplace in telecommunications and sensor applications. However the fabrication of low-loss optical fiber tapers with subwavelength diameters was previously thought to be impractical due to difficulties associated with control of the surface roughness and diameter uniformity. In this paper we show that very-long ultra-low-loss tapers can in fact be produced using a conventional fiber taper rig incorporating a simple burner configuration. For single-mode operation, the optical losses we achieve at 1.55microm are one order of magnitude lower than losses previously reported in the literature for tapers of a similar size. SEM images confirm excellent taper uniformity. We believe that these low-loss structures should pave the way to a whole range of fiber nanodevices.

585 citations



Journal ArticleDOI
01 Mar 2000-Microbiology
TL;DR: It is amongst the Bacteria and Archaea that respiratory flexibility can be found at its most extreme and contributes to the ability of prokaryotes to colonize many of Earth’s most hostile microoxic and anoxic environments.
Abstract: The respiration of oxygen is fundamental to the life of higher animals and plants. The basic respiratory process in the mitochondria of these organisms involves the donation of electrons by low-redox-potential electron donors such as NADH. This is followed by electron transfer through a range of redox cofactors, bound to integral membrane or membrane-associated protein complexes. The process terminates in the reduction of the high-redox-potential electron acceptor, oxygen (Fig. 1). The free energy released during this electrontransfer process is used to drive the translocation of protons across the mitochondrial membrane to generate a trans-membrane proton electrochemical gradient or protonmotive force (∆p) that can drive the synthesis of ATP (Fig. 1). The respiratory flexibility of the mammalian mitochondrion is rather poor. There is some flexibility at the level of electron input (Fig. 1), but none at the level of electron output where cytochrome aa $ oxidase provides the only means of oxygen reduction. In the case of plant mitochondria, a slightly greater degree of respiratory flexibility is encountered with a number of alternative NADH dehydrogenases and two oxidases being apparent. This respiratory flexibility affords plant mitochondria with the capacity to contribute to processes other than the generation of ATP. For example, electron transfer from the alternative NADH dehydrogenase to the alternative oxidase is not coupled to the generation of ∆p and instead serves to release energy as heat, which can volatilize insect attractants to aid pollination. In the American skunk cabbage this same mechanism for heat production serves to permit growth at subzero temperatures (Nicholls & Ferguson, 1992). There is also some respiratory flexibility in the mitochondria of yeast, filamentous fungi and ancient protozoa, but it is amongst the Bacteria and Archaea that respiratory flexibility can be found at its most extreme. In these organisms, a diverse range of electron acceptors can be utilized including elemental sulphur and sulphur oxyanions (Hamilton, 1998), organic sulphoxides and sulphonates (Lie et al., 1999; McAlpine et al., 1998), nitrogen oxy-anions and nitrogen oxides (Berks et al., 1995), organic N-oxides (Czjzek et al., 1998), halogenated organics (Dolfing, 1990; Louie & Mohn, 1999; van de Pas et al., 1999), metalloid oxy-anions such as selenate and arsenate (Krafft & Macy, 1998; Macy et al., 1996, 1993; Schroder et al., 1997), transition metals such as Fe(III) and Mn(IV) (Lovley, 1991), and radionuclides such as U(VI) (Lovley & Phillips, 1992) and Tc(VII) (Lloyd et al., 1999). This respiratory diversity can be found amongst pyschrophiles, mesophiles and hyperthermophiles and contributes to the ability of prokaryotes to colonize many of Earth’s most hostile microoxic and anoxic environments.

514 citations


Cited by
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28 Jul 2005-
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations


Journal Article
Abstract: On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0×10(-21). It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203,000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410(-180)(+160) Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

4,375 citations


Journal Article
Abstract: Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

3,967 citations


Journal ArticleDOI
17 Jan 2003-Science
Abstract: Photonic crystal fibers guide light by corralling it within a periodic array of microscopic air holes that run along the entire fiber length Largely through their ability to overcome the limitations of conventional fiber optics—for example, by permitting low-loss guidance of light in a hollow core—these fibers are proving to have a multitude of important technological and scientific applications spanning many disciplines The result has been a renaissance of interest in optical fibers and their uses

3,758 citations


01 Feb 2015-
Abstract: The reference human genome sequence set the stage for studies of genetic variation and its association with human disease, but epigenomic studies lack a similar reference. To address this need, the NIH Roadmap Epigenomics Consortium generated the largest collection so far of human epigenomes for primary cells and tissues. Here we describe the integrative analysis of 111 reference human epigenomes generated as part of the programme, profiled for histone modification patterns, DNA accessibility, DNA methylation and RNA expression. We establish global maps of regulatory elements, define regulatory modules of coordinated activity, and their likely activators and repressors. We show that disease- and trait-associated genetic variants are enriched in tissue-specific epigenomic marks, revealing biologically relevant cell types for diverse human traits, and providing a resource for interpreting the molecular basis of human disease. Our results demonstrate the central role of epigenomic information for understanding gene regulation, cellular differentiation and human disease.

3,734 citations


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Performance
Metrics

Author's H-index: 111

No. of papers from the Author in previous years
YearPapers
202158
202054
201970
201856
201793
201682

Top Attributes

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Author's top 5 most impactful journals

Optics Express

125 papers, 5.9K citations

Optics Letters

80 papers, 4.8K citations

IEEE Photonics Technology Letters

77 papers, 2K citations

Journal of Lightwave Technology

69 papers, 2.5K citations

Electronics Letters

43 papers, 2.8K citations