We review the present state-of-the-art for air-guiding photonic bandgap fibers. Applications, loss mechanisms and future work is considered.

We report on the latest development within active photonic crystal fibers for high power lasers and amplifiers with special focus on how the fibers can be improved with both polarization-maintaining and polarizing properties. We describe rod-type fibers for which a record-high power extraction of 250W/m is achieved. Moreover. we describe how active characterization is used to optimize fibers for laser and amplifier sub-assemblies with respect to beam quality, efficiency and robustness. Finally, we illustrate how the fibers can be integrated with high NA tapers and passive air-clad fibers containing Bragg grating to form an all-fiber. alignment-free, high-power fiber laser subassembly.

A model for calculating the time necessary for filling one or more specific holes in a photonic crystal fibre is made. This model is verified for water, and its enabling potential is illustrated by a polymer application. Selective filling of the core in an air-guide photonic crystal fibre is demonstrated for a polymer and for water. Launching light into such a hybrid-material core proves to be very easily done. Finally, a scheme for enabling access to the core alone, by use of a fusion splicer, is presented.

Selective coupling to the fundamental mode of short hollow-core photonic bandgap fibres without exciting cladding modes is improved by gold-coated fibre end facets. Cladding modes are suppressed by 20-30 dB for single-and multimode fibre launch, respectively, while in-band power loss is 3-8 dB.

The first data transmission over air-guiding photonic bandgap (PBG) fibre is demonstrated. A 10 Gbit/s signal was successfully transmitted at 1550 nm over 150 m of singlemode PBG fibre, thus demonstrating their applicability to optical communications. Furthermore, the impact of the polarisation properties of PBG fibres is highlighted experimentally.

A new class of hollow-core Bragg fibers1 composed of concentric cylindrical silica rings separated by nanoscale support bridges is presented.2, 3 These fibers are believed to be especially useful for high-power delivery of light within a broad wavelength range or at multiple wavelength bands. We experimentally observe theoretically predicted hollow-core confinement over an octave frequency range. The bandwidth of bandgap guiding in this type of Bragg fiber far exceeds that of other hollowcore fibers reported in the literature. With the record-low number of three rings of silica cladding layers, these Bragg fibers achieve a propagation loss of the order of 1 dB/m. The concept of hollowcore Bragg fibers, in which the fiber cladding is composed of cylindrical dielectric layers with alternating refractive indices, was first proposed in 1978.1 Cregan et al. demonstrated another class of hollow-core fibers, namely, photonic crystal fibers, in which the cladding structure is formed by creating a twodimensional array of airholes in a highindex material, typically silica.4 In general, the transmission coefficient through a planar Bragg reflector, which translates to a leakage coefficient of the Bragg fiber, depends exponentially on the number of layers.5, 6 We consider a specific Bragg fiber with a hollow-core radius of 10 μm. The fiber cladding is formed by three layers with a refractive index of 1.45 and average thickness of 370 nm, separated by 4.10m-thick air layers. In practice, support bridges must be introduced to separate the adjacent silica rings. Assuming mass conservation throughout the fiber pulling process, we estimate the support bridge thickness to be in the area of 45 nm, which is in reasonable agreement with the results obtained with scanning electron microscopes. Because the support bridges are much smaller than the wavelength of interest, we can, to a good approximation, neglect the presence of these support bridges and regard the region between the highindex silica layers as composed entirely of air. An interesting feature that will further inspire the development of this type of fiber is that, with only four silica layers, theoretical considerations predict that the fiber leakage loss can be reduced to less than 0.1dB/km. Also, the Bragg fiber supports low-loss modes (less than 1dB/m) in the 0.82–2.86m wavelength range, which is almost two octaves in frequency range, and also in a wavelength interval in which material losses are so high that one could indeed benefit from an air core of the fiber. T. Sorensen (thors@ com.dtu.dk), J. B. Jensen, T. P. Hansen and A. Bjarklev are with Research Center COM, Technical University of Denmark, Lyngby, Denmark. H. J. Deyerl is with the Abteilung fur Ionenphysik, Technische Universitat Chemnitz, Germany. Y. Xu, Y. Huang, M. Terrel, R. K. Lee and A. Yariv are with the California Institute of Technology, Pasadena, Calif. G. Vienne is with the Center for Advanced Research in Photonics, Chinese University of Hong Kong, Shatin, Hong Kong. C. Jakobsen, T. P. Hansen, J. Broeng and H. Simonsen are with Crystal Fibre A/S, Birkerod, Denmark. N. A. Mortensen is with the Department of Micro and Nanotechnology, Technical University of Denmark, Lyngby, Denmark.

Photonic Crystal Fibers (PCF’s) are silica based optical fibers with tiny air running along the length of the fiber. These fibers allows for a close proximity of the light guided in the fiber and molecules positioned in the air holes. The penetration of the optical field into the air holes can be significant [1], making PCF’s potential candidates for sensor applications. In the present work we have used a hollow-core fiber from Crystal Fibre A/S for molecular immobilization and detection of DNA and protein molecules, respectively.

A 22-fold pulse-duration compression around 1µm wavelength is achieved in an air-guiding, anomalously dispersive photonic-crystal-fibre. 3.6ps pulses from a Yb fibre laser are compressed to 163fs in the totally-fibre integrated format. Peak power/energy scalability is feasible.

For development of hollow-core transmission fibers, the realizable fibers lengths, bandwidth, characterization, and compatibility with standard technology are important issues. We report record-length air-guiding fiber, spectral properties, splicing, and optical time domain reflectometer (OTDR) measurements. Furthermore, spectral macrobending loss measurements for two different designs of air-core photonic bandgap fibers are presented. While bending loss is observed, it does not limit operation for all practical bending diameters (>5 mm).

Get PDF Email Share Share with Facebook Tweet This Post on reddit Share with LinkedIn Add to CiteULike Add to Mendeley Add to BibSonomy Get Citation Copy Citation Text Jesper Riishede, Jesper Lægsgaard, Jes Broeng, Anders Bjarklev, Fei Lu, Wayne H. Knox, T. Sørensen, Y. Xu, G. Vienne, C. Jakobsen, H. J. Deyerl, J. B. Jensen, T. P. Hansen, Y. Huang, M. Terrel, R. K. Lee, N. A. Mortensen, J. Broeng, H. Simonsen, A. Bjarklev, and A. Yariv, "Fiber Optics," Optics & Photonics News 15(12), 26-28 (2004) Export Citation BibTex Endnote (RIS) HTML Plain Text Citation alert Save article

We report on experimental studies of gas sensing using air-guiding photonic bandgap fibers. The photonic bandgap fibers have at one end been spliced to standard single mode fibers for ease of use and improved stability

Air-cored, photonic band-gap crystal fibers exhibiting low nonlinearity and anomalous chromatic dispersion in spectral ranges inaccessible to conventional fibers can be used in the realization of all-fiber-format pulse compressors with unprecedented peak powers and wavelength diversity. Linear compression of inherently chirped and prestretched pulses by factors ranging from 20 to 80 around 1.0 and 1.5 microm have allowed generation of pulses as short as 163 fs. The results show that totally integrated femtosecond fiber laser sources can be realized throughout the visible and near-infrared and point to the possibility of megawatt peak and tens of watt average in-fiber power levels.

Laser damage thresholds of 8 mum- and 22 mum-core diameter solid-core photonic crystal fibres (PCF) and hollow-core photonic band gap (PBG) fibres have been measured. The studies were carried out using a 1.06 mum Nd:YAG laser (30 nsec pulses at 10 Hz), which is optimally coupled into these fibres by careful mode matching, providing a coupling efficiency greater than 90%. It has been shown that the damage threshold of the 8 mum core PBG fibre occurs at pulse energies close to 1 mJ, equivalent to a fluence well in excess of 1 kJ/cm(2) propagating down the fibre. This is a factor of 4 larger than the damage threshold of a solid-core PCF of similar core diameter. In comparison, the damage threshold of the large-core PBG is smaller than that of the equivalent PCF. Theoretical modelling based only on the optical modal properties of the single-mode PBG fibre shows that an enhancement by a factor of 25 should be obtainable. Thus there are different damage mechanisms potentially responsible for the fragility of larger-core PBG fibres. In an experimental study of bend losses it has been found that it is possible to bend the 8 mum PBG fibre up to the breaking point bend radius (<1 mm). The critical bend radius for the 22 mum core PBG is close to 2 mm, which is 50 times smaller than the critical bend radius of a 20 mum core PCF.

Recent development achievements in high power fiber laser designs and subassemblies have improved the performance and usability. Such achievements show the path for these fiber lasers out of the R&D labs and into industrial environments.

We study the dispersion of an air-core photonic bandgap fiber and show its application in chirped pulse amplification. ~500 fs pulses, stretched to ~ 100 ps using dispersion-compensating fiber, were re-compressed to ~1ps in 10 m of this fiber

A 22-fold pulse-duration compression around 1 mum is achieved in an air-guiding anomalously dispersive photonic-crystal-fibre. 3.6 ps pulses from an Yb-fibre laser are compressed to 163 fs in the totally-fibre integrated format. Peak/average power scalability is feasible