Microstructured Optical Fibres

This group is part of the Advanced Fibre Technologies & Applications Group

In recent years, two new types of optical fibre have revolutionised this dynamic field, bringing with them a wide range of novel optical properties. These new fibres, known collectively as microstructured fibres, can be made entirely from one type of glass as they do not rely on dopants for guidance. Instead, the cladding region is peppered with many small air holes, that run the entire fibre length. These fibres are typically separated into two classes, defined by the way in which they guide light:

• Holey fibres, in which the core is solid and light is guided by a modified form of total internal reflection as the air holes lower the effective refractive index of the cladding relative to that of the solid core.
• Photonic band-gap fibres, in which guidance in a hollow core can be achieved via photonic band-gap effects. The many varieties of microstructured fibres are discussed in more detail in the following sections.

Within the group we have the full range of expertise required to design, fabricate and characterise both forms of microstructured fibre, both in silica and in compound glass. We also run a large number of end application projects both in close collaboration with a range of other ORC groups, and with other external academic and industrial partners. Current collaborating organisations include amongst others: ETH Zurich, University of Dijon, Cambridge University, Mullard Space Centre, SPI Lasers Ltd, Furukawa, Hovermere Ltd, BAe Systems and SELEX.

Current projects Active project areas include amongst others: High nonlinearity dispersion-controlled MOFs Nonlinearity control in MOFs Fibres for supercontinuum generation Space applications of MOFs Tapered MOF devices Gas sensing using MOFs Broadband/low loss Photonic Bandgap Fibres MOFs for mid-IR applications Compound glass MOFs MOFs for laser beam delivery MOF laser devices Large mode area MOFs

Supervisors: Prof. D. J. Richardson and Dr Francesco Poletti

Ultra-low loss photonic bandgap fibres

Hollow core Photonic bandgap fibres (PBGFs) are a new and revolutionary type of optical fibre where light is guided in air rather than in glass. For this reason, these fibres present radically new optical characteristics, such as an extremely low nonlinearity and a potentially ultra-low transmission loss. As a consequence they have the potential to replace conventional optical fibres in long distance telecoms transmissions. This ambitious project, part of a major collaborative European effort, will address and try to solve the main outstanding issues which currently prevent PBGF technology having a revolutionizing impact on optical communications.

During the project, the student will employ advanced computational methods to optimise fibre designs using photonic bandgap and antiresonant effects; collaborate with glass scientists and fibre fabricators to identify the limiting source of loss and optimise the fibre material composition accordingly; and will implement and develop new experimental techniques to characterise the physical and optical properties of various fabricated fibres.

Due to the challenging nature of the project we are looking for an outstanding and highly motivated candidate able to work effectively within a large collaborative network and willing to engage in a range of diverse scientific activities.

Investigation of nonlinear optical effects in novel hollow core fibres

Hollow core glass fibres, confining light by total external reflection, optical antiresonance or photonic bandgap effects, have recently opened up new routes for generating efficient nonlinear effects in gaseous or liquid media. The tremendous potential of these novel gas or liquid filled nonlinear waveguides for both pure science and device applications has generated significant interest in the fibre optics community. As a consequence, several new fibre types have been recently demonstrated. However, a number of intriguing questions, such as how best to exploit antiresonance effects in a hollow waveguide or how to combine them effectively with photonic bandgaps, are still very much open for investigation.

This project aims to provide an answer to these questions and a deeper physical understanding of the physical waveguiding mechanisms in these fibres. It will also aim to develop novel fibre types with tailored spectral transmission bandwidths and optical properties, and employ them in the experimental study of nonlinear processes at high field intensities in gases and liquids. The student will engage in the physical modelling of these novel fibres and in numerical simulations of their optical properties. He will also develop tools for simulating the thermal, fluid-dynamics and structural deformation processes occurring during the fabrication of these fibres, and will finally conduct nonlinear experiments with the fabricated waveguides. These experiments, which may comprise ultra-high spectral density supercontinuum generation, ultrashort pulse generation through pulse self compression, phase coherent comb generation and high harmonic generation, will be conducted in collaboration with an extensive and established network of experimental partners at the ORC and more broadly in Europe.

J.C.Flanagan, D.J.Richardson, M.J.Foster, I.Bakalski, Microstructured fibers for broadband wavefront filtering in the mid-IR, Optics Express 2006 Vol.14(24) pp.11773-11786

J.H.V.Price, T.M.Monro, H.Ebendorff-Heidepriem, F.Poletti, V.Finazzi, J.Y.Y.Leong, P.Petropoulos, J.C.Flanagan, G.Brambilla, X.Feng, D.J.Richardson, Mid-IR supercontinuum generation in non-silica glass fibers, Photonics West San Jose, California 21-26 Jan 2006 (Invited)

J.C.Baggett, T.M.Monro, K.Furusawa, D.J.Richardson, Understanding bending losses in holey optical fibers, Optics Communications 2003 Vol.227 pp.317-335

M.L.V.Tse, P.Horak, J.H.V.Price, F.Poletti, F.He, D.J.Richardson, Pulse compression at 1.06 microns in dispersion-decreasing holey fibers, Optics Letters 2006 Vol.31(23) pp.3504-3506

R.Amezcua-Correa, N.G.Broderick, M.N.Petrovich, F.Poletti, D.J.Richardson, Optimizing the usable bandwidth and loss through core design in realistic hollow-core photonic bandgap fibers, Optics Express 2006 Vol.14(17) pp.7974-7985

F.Poletti, N.G.R.Broderick, D.J.Richardson, T.M.Monro, The effect of core asymmetries on the polarization properties of hollow core photonic bandgap fibers, Optics Express 2005 Vol.13(22) pp.9115-9124

J.Y.Y.Leong, S.Asimakis, F.Poletti, P.Petropoulos, X.Feng, R.C.Moore, K.E.Frampton, T.M.Monro, H.Ebendorff-Heidepriem, W.H.Loh, D.J.Richardson, Towards zero dispersion highly nonlinear lead silicate glass holey fibres at 1550nm by structured-element-stacking, ECOC 2005 Glasgow 25-29 Sep 2005 (Postdeadline)

F.Poletti, V.Finazzi, T.M.Monro, N.G.R.Broderick, V.Tse, D.J.Richardson, Inverse design and fabrication tolerances of ultra-flattened dispersion holey fibers, Optics Express 2005 Vol.13 pp.3728-3736

M.N.Petrovich, R.Amezcua-Correa, N.G.Broderick, D.J.Richardson, T.Delmonte, M.A.Watson, E.J.O'Driscoll, Photonic bandgap fibres for broadband transmission of SWIR wavelengths, EMRS-DTC Technical Conference Edinburgh 13-14 Jul 2006