Plenary Speakers

Jonathan Knight Roy Taylor Yoel Fink

Centre for Photonics and
Photonic Materials,
Department of Physics,
University of Bath,
United Kingdom

Femtosecond Optics Group
Imperial College London,
United Kingdom

Photonic Bandgap Fibers
& Devices Group,
Massachusetts Institute of

Optics in microstructured and photonic crystal fibers High power fibre integrated supercontinuum sources Towards multimaterial multifunctional fibers that see, hear, sense and communicate
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Jonathan Knight - University of Bath / United Kingdom
The development of optical fibres with two-dimensional patterns of air holes running down their length has reinvigorated research in the field of fibre optics. It has greatly ľ and fundamentally ľ broadened the range of speciality optical fibres, by demonstrating that optical fibres can be more ôspecialö than previously thought. Fibres with air cores have made it possible to deliver energetic femtosecond-scale optical pulses, transform limited, as solitons using single-mode fibre. These pulses spectacularly self-destruct in any conventional single-mode fibre, if they do not destroy the fibre itself. Other fibres with anomalous dispersion at visible wavelengths have spawned a new generation of single-mode optical supercontinuum sources, spanning visible and near-infrared wavelengths and based on compact pump sources. Such sources have rapidly spread through optical laboratories and are now commercially available, generating a range of applications in areas such as sensing and biomedical optics. A third example is in the field of fibre lasers, where the use of photonic crystal fibre concepts has led to a new hybrid laser technology, in which the very high numerical aperture available when air holes are incorporated into the fibre have made it possible to form high-power fibre lasers which are so short that they are more naturally held straight than bent. This talk will describe the basic physics and technology behind these developments, illustrated with some of the impressive demonstrations of the past 18 months.

J. Roy Taylor - Imperial College / United Kingdom
Since the advent of photonic crystal fibres (PCF) there has been significant and renewed interest in the development, characterization and basic studies of supercontinuum generation driven by the increased applications possibilities of these unique and efficient systems. The design and manufacture of micro structured optical fibre (MOF/PCF) has allowed unprecedented control of the parameters that affect efficient in-fibre nonlinear processes, such as manipulation of the mode field diameter to enhance or inhibit nonlinearity or by shifting of the zero dispersion wavelength to allow soliton generation in previously unattainable spectral regions. While much of the underlying physics and contributing non linear optical processes have been known since the 1980s most recent theoretical work has revisited and reexamined the variety of nonlinear interactions in these structures under a variety of pump conditions and remarkable agreement between theoretical prediction and experimental realization has been achieved. It may appear that work in this field is close to complete but there are still challenges remaining to be addressed. Some of which will be considered here. One of the simplest supercontinuum sources is the cw pumped scheme, which we highlight. For example power scaling improvements in the spectral bandwidth, together with spectral extension need to be addressed, as well as techniques to shape or spectrally flatten outputs. Here we will describe our development programmes on high power, fibre laser pumped and fully fibre integrated supercontinuum sources, with the emphasis on simpler cw pumped schemes, which to date have provided the highest spectral power densities available, both in conventional fibre and PCF formats. Continua based upon 1 Ám Yb fibre laser pumps have traditionally been limited by the high water losses in PCF at 1.38 Ám, although extension beyond 1.38 Ám using low water loss PCFs has been demonstrated. Here the water loss problem is minimized by using a short length of relatively conventional PCF and by scaling the pump power which also aids the increase in the spectral power density. Ultimately we generate a supercontinuum spanning from 1.06 to 1.67 Ám with 29 W of output power using a 50 W Yb fiber pump laser and increased power scaling will also be described. This corresponds to a spectral bandwidth of 600 nm at 8 dB and a power density of more than 50 mW/nm up to 1.4 Ám. Experimental output spectra agree very well with our theoretical predictions.

Yoel Fink - Massachusetts Institute of Technology / USA
Virtually all electronic and optoelectronic devices necessitate a challenging assembly of conducting, semiconducting and insulating materials into specific geometries with low-scattering interfaces and microscopic feature dimensions. A variety of wafer-based processing approaches have been developed to address these requirements, which although successful are at the same time inherently restricted by the wafer size, its planar geometry and the complexity associated with sequential high-precision processing steps. In contrast, optical-fiber drawing from a macroscopic preformed rod is simpler and yields extended lengths of uniform fibers. Recently, a new family of fibers composed of conductors, semiconductors and insulators has emerged. These fibers share the basic device attributes of their traditional electronic and optoelectronic counterparts, yet are fabricated using conventional preform-based fiber-processing methods, yielding kilometres of functional fiber devices. Two complementary approaches towards realizing sophisticated functions are explored: on the single-fiber level, the integration of a multiplicity of functional components into one fiber, and on the multiple-fiber level, the assembly of large-scale two- and three-dimensional geometric constructs made of many fibers. When applied together these two approaches pave the way to multifunctional fabric systems.