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T.A. Birks

Bio: T.A. Birks is an academic researcher from University of Bath. The author has contributed to research in topics: Photonic-crystal fiber & Photonic crystal. The author has an hindex of 18, co-authored 37 publications receiving 1938 citations.

Papers
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Journal ArticleDOI
TL;DR: In this paper, the waveguiding properties of a new type of low-loss optical waveguide have been reported, where the photonic crystal fiber can be engineered to support the fundamental guided mode at every wavelength within the transparency window of silica.
Abstract: We report on the waveguiding properties of a new type of low-loss optical waveguide. The photonic crystal fiber can be engineered to support only the fundamental guided mode at every wavelength within the transparency window of silica. Experimentally, a robust single mode has been observed over a wavelength range from 337nm to beyond 1550nm (restricted only by available wavelength sources). By studying the number of guided modes for fibers with different parameters and the use of an effective index model we are able to quantify the requirements for monomode operation. The requirements are independent of the scale of the fiber for sufficiently short wavelengths. Further support for the predictions of the effective index model is given by the variation of the spot size with wavelength,

411 citations

Journal ArticleDOI
TL;DR: The properties of photonic crystal fibers with large air holes can be modeled by a silica rod in air as mentioned in this paper, and it has been shown that the dispersion of such fibers could exceed -2000 ps/mm/km, or they could compensate (to within /spl plusmn/0.2%) the length of standard fiber over a 100nm range.
Abstract: The properties of photonic crystal fibers with large air holes can be modeled by a silica rod in air. Such approximate calculations show that the dispersion of photonic crystal fibers could exceed -2000 ps/mm/km, or they could compensate (to within /spl plusmn/0.2%) the dispersion of 35 times their length of standard fiber over a 100-nm range.

337 citations

Journal ArticleDOI
TL;DR: In this paper, the interaction of all-fiber acousto-optic devices based on the null fused taper coupler has been extensively analyzed under a set of approximations that are valid in most cases.
Abstract: All-fiber acousto-optic devices based on the null fused taper coupler have been successfully demonstrated as frequency shifters, variable splitters, switches and tunable filters. In this paper, the interaction upon which these devices are based has been extensively analyzed under a set of approximations that are valid in most cases. Simple analytical expressions for the important properties are derived, which provide a set of design rules for such devices.

202 citations

Journal ArticleDOI
TL;DR: In this paper, the authors report measurements of group velocity dispersion in photonic crystal fiber using low coherence techniques and confirm theoretical predictions that photonic fiber, unlike conventional step-index fiber, can exhibit anomalous waveguide dispersion while remaining singlemode.
Abstract: The authors report measurements of group velocity dispersion in photonic crystal fibre using low coherence techniques. The results confirm theoretical predictions that photonic crystal fibre, unlike conventional step-index fibre, can exhibit anomalous waveguide dispersion while remaining singlemode. This allows the design of singlemode fibres with zero dispersion points at wavelengths much shorter than is possible in standard fibre.

156 citations

Journal ArticleDOI
TL;DR: In this paper, light is coupled from the guided mode along one tapered optical fiber into the whispering gallery modes around the circumference of another by tracking, at different points along it, the wavelengths at which these modes exist.
Abstract: Light is coupled from the guided mode along one tapered optical fiber into the whispering gallery modes around the circumference of another. Small diameter variations in the second fiber are measured by tracking, at different points along it, the wavelengths at which these modes exist. The measurement does not require any optical alignment, and its resolution can be 1 part in 10 000 or better.

151 citations


Cited by
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Journal ArticleDOI
17 Jan 2003-Science
TL;DR: In this article, a periodic array of microscopic air holes that run along the entire fiber length are used to guide light by corralling it within a periodic arrays of microscopic holes.
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

3,918 citations

Journal ArticleDOI
TL;DR: In this paper, the authors present a survey of the use of Wannier functions in the context of electronic-structure theory, including their applications in analyzing the nature of chemical bonding, or as a local probe of phenomena related to electric polarization and orbital magnetization.
Abstract: The electronic ground state of a periodic system is usually described in terms of extended Bloch orbitals, but an alternative representation in terms of localized "Wannier functions" was introduced by Gregory Wannier in 1937. The connection between the Bloch and Wannier representations is realized by families of transformations in a continuous space of unitary matrices, carrying a large degree of arbitrariness. Since 1997, methods have been developed that allow one to iteratively transform the extended Bloch orbitals of a first-principles calculation into a unique set of maximally localized Wannier functions, accomplishing the solid-state equivalent of constructing localized molecular orbitals, or "Boys orbitals" as previously known from the chemistry literature. These developments are reviewed here, and a survey of the applications of these methods is presented. This latter includes a description of their use in analyzing the nature of chemical bonding, or as a local probe of phenomena related to electric polarization and orbital magnetization. Wannier interpolation schemes are also reviewed, by which quantities computed on a coarse reciprocal-space mesh can be used to interpolate onto much finer meshes at low cost, and applications in which Wannier functions are used as efficient basis functions are discussed. Finally the construction and use of Wannier functions outside the context of electronic-structure theory is presented, for cases that include phonon excitations, photonic crystals, and cold-atom optical lattices.

2,217 citations

Journal ArticleDOI
TL;DR: The history, fabrication, theory, numerical modeling, optical properties, guidance mechanisms, and applications of photonic-crystal fibers are reviewed.
Abstract: The history, fabrication, theory, numerical modeling, optical properties, guidance mechanisms, and applications of photonic-crystal fibers are reviewed

1,488 citations

Journal ArticleDOI
20 Nov 1998-Science
TL;DR: A fundamentally different type of optical waveguide structure is demonstrated, in which light is confined to the vicinity of a low-index region by a two-dimensional photonic band gap crystal.
Abstract: A fundamentally different type of optical waveguide structure is demonstrated, in which light is confined to the vicinity of a low-index region by a two-dimensional photonic band gap crystal. The waveguide consists of an extra air hole in an otherwise regular honeycomb pattern of holes running down the length of a fine silica glass fiber. Optical fibers based on this waveguide mechanism support guided modes with extraordinary properties.

1,290 citations

Journal ArticleDOI
TL;DR: In this article, different properties possible to obtain in photonic crystal fibers are reviewed and fabrication and modeling methods are also discussed, and different properties of photonic bandgap effect are discussed.
Abstract: Photonic crystal fibers are a new class of optical fibers. Their artificial crystal-like microstructure results in a number of unusual properties. They can guide light not only through a well-known total internal reflection mechanism but using also photonic bandgap effect. In this paper different properties possible to obtain in photonic crystal fibers are reviewed. Fabrication and modeling methods are also discussed.

995 citations