1,721,177 research outputs found
Nonlinearity in holey optical fibers: measurement and future opportunities - errata
No full textErrata to Nonlinearity in holey optical fibers: measurement and future opportunities. (1999) Optics Letters, 24 (20), 1395-1397. (doi:10.1364/OL.24.001395).Broderick, N.G.R., Monro, T.M., Bennett, P.J. and Richardson, D.J. <br/
Nonlinear and acoustic properties of holey optical fibres
No full textThe 'holey fibre' (HF) is a new class of optical fibre which has a cladding formed by a number of air holes which run along the length of the fibre. Typical HFs are shown in Figures 1 and 2. These fibres can be made from a single material, and guidance is provided by the difference in effective indices between the core and the 'holey' cladding. The microstructured transverse profile opens up a diverse range of novel optical properties, many of which are not possible in more conventional fibre structures. For example, HFs can have anomalous waveguide dispersion at visible wavelengths and be single-mode, which is impossible in conventional fibers
Communications Revolution. New Technology for Communications
No full textOver the past century, the development of communications technology has had a dramatic impact on our way of life. It is now possible to phone people almost anywhere in the world, the one mobile phone can work in every continent, and researchers in Antarctica have ready access to EMAIL services! Historians of the future looking back on the late 20th/early 21st century will probably use the word "globalization" to describe this time.In this chapter, I will present an overview of the concepts and technology used in modern communications systems. These systems rely on fundamental principles such as light scattering, optical excitation of electrons and superposition of waves, and it is necessary to draw on physical principles ranging from ray optics through to quantum optics. The story begins with a brief chronological description of the breakthroughs that have enabled the development of modern communications systems
Microstructured fibres: moulding the properties of light
No full textThe combination of wavelength-scale features and geometric flexibility offered by microstructured or holey optical fibres (HFs) leads to a significantly broader range of optical properties than is possible in conventional optical fibres (see the examples in Figure 1). These properties include single-mode guidance at all wavelengths, novel dispersion properties including broadband dispersion flattening and anomalous dispersion at visible wavelengths, mode size tailoring over three orders of magnitude, and many more. The optical properties of holey fibres are determined by the size, shape and locations of the air holes that define the cladding region. HFs can be made either from a single material (eg pure silica) or can be doped, which allows active fibre devices to be made. Progress in this rapidly emerging technology will be reviewed, ranging from modelling and fabrication through to applications and practical devices
Microstructured optical fibers
No full textThe development of core-clad silica glass optical fibers has revolutionized communications systems over the past 30 years. These 'conventional' optical fibers have also made a significant impact in areas as diverse as sensing, medical imaging, laser welding and machining, and the realization of new classes of lasers and amplifiers. All of these advances have been enabled by one key factor: the reduction of the fiber loss. Reducing loss was a topic of intensive research and development for two decades, and dramatic improvements in the transmission of silica-based fibers in the 1.5 micron telecommunications window were achieved as a result. The widely used Coming SMF-28 fiber has a loss of less than 0.2 dB/km at 1550nm. In the early 1970s, when the fabrication processes for the manufacture of core-clad preforms had not yet reached maturity, Kaiser et al. proposed an alternative route to achieving low fibre losses. Kaiser’s concept was to confine light within a pure (undoped) silica core by surrounding it with air [1], [2]. The core was supported by a sub-wavelength strand of silica glass and then jacketed in a silica cladding for strength. Although this new class of fibers showed promise, the fabrication methods used to produce these early single-material fibers were limited, and this new technology was quickly overtaken by improvements in the MCVD (modified chemical vapour deposition process), which allowed the definition of high quality preforms for the production of low loss core-clad silica fibres. In the late 1980s, work by Yablonovitch [3] on the development of three dimensional photonic crystals identified micron-scale structuring to be a powerful means of modifying the optical characteristics of a material. The earliest photonic crystal samples were formed by drilling cm-scale holes to produce photonic bandgaps within which light propagation was forbidden. These samples were confirmed to have photonic bandgaps located at microwave wavelengths. In the 1990s, a number of groups worked to extend this concept to infrared and visible wavelengths by scaling down the dimensions of the photonic crystal structure to micron-scale feature sizes. The technique that has been used most extensively for defining two dimensional photonic crystals is electron beam lithography [4]. However, this technique is not well suited for defining structures that are truly extended in the third dimension to avoid non-uniformities in this direction modifying the properties of the photonic bandgaps. Fabricating two dimensional photonic crystals is an engineering challenge, and although a number of approaches exist, there is a continued drive to develop cheap and flexible techniques for the large scale production of hgh quality photonic crystals. In 1995, Birks et al. proposed a novel technique for producing two dimensionally structured silica/air photonic crystal structures by taking advantage of optical fiber manufacturing techniques [5] . The fabrication concept was to stack macroscopic silica capillary tubes together into a hexagonal lattice to form a preform with mm-scale features, and then to pull this preform to a fiber with micron-scale features on a drawing tower. Thus the scale reduction and longitudinal uniformity inherent to the fiber drawing process could be utilized to produce tlie first photonic crystals that could truly be considered infinite in the third dimension. etc
Erratum. Exploration of self-writing and photosensitivity in ion-exchanged waveguides: J. Opt. Soc. Am. B (2003) 20 (6) (1317-1325) DOI: 10.1364/JOSAB.20.001317
No full textModelling confinement loss in practical small-core holey optical fibres
No full textMicrostructured optical fibres (MOFs) are all-silica fibres that guide light by means of an arrangement of air-holes that run down the entire fibre length. In the kind of MOFs here considered, also named holey fibres (HFs), guidance arises from average-index effects: the holes form the cladding region around the solid core. The modes of such fibres are leaky because the core refractive index is the same as the index beyond the (finite) cladding region. HFs with a core diameter of the scale of an optical wavelength and large holes have been fabricated, resulting in the smallest effective area ever measured in a fibre at 1550 nm [1]. Such small effective areas make these fibres attractive for nonlinear applications. The cladding of a HF is usually comprised of hexagonally-packed rings of holes, and when the hole-to-hole spacing (Lambda) is of the order of the wavelength, several rings of holes are required to reduce the confinement loss to a practical value. Fibre fabrication feasibility on the other hand constrains the number of rings that can be used. Therefore in order to optimise the design of this class of fibres, it is necessary to study the loss characteristics for small-core HFs
Self-writing a depressed index waveguide in bulk glass
No full textWe use numerical simulations to predict the first complex self-written structure in a bulk material. A depressed-index "pipe" structure, which guides light like a channel, is created using a Laguerre-Gaussian "donut" beam
Leaky modes in microstructured optical fibres with annular sectors
No full textMicrostructured or holey optical fibres are a novel class of fibres that have attracted much interest recently because they can be tailored to have properties (dispersion, nonlinearity, mode size) very different from conventional fibres. These structures can consist exclusively of air holes arranged around a solid core region in a uniform background. Since such fibres do not have any raised index regions, they cannot support true bound modes. They can, however, possess leaky modes where the light is trapped within a region surrounded by air holes. Such modes suffer confinement losses due to energy leakage between and through the holes. The confinement loss is given by the imaginary part of the complex effective mode index neff. Existing basis function expansion (Galerkin) techniques (using plane waves [1] or Hermite-Gaussians [2]) give most modal properties except for the confinement loss. Methods such as BPM can be used to find confinement loss [3] but are numerically intensive; and, recently, a multipole method has been used which is restricted to circular holes [4]. The technique presented here has the simplicity of a Galerkin technique but can also find confinement loss and complements existing methods by applying to a holes in the shape of annular sectors. Typical structures are shown below.& more ..
Self-written channels in ion-exchanged waveguides; experiment and modelling of photosensitivity
No full textWe demonstrate that a channel waveguide can be self-written in ion-exchanged Nd-doped glass. The initial stages of the waveguide evolution are used to develop a phenomenological model of the photosensitivity process occurring within this material
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