Showing papers by "Kim P. Hansen published in 2003"
17 Nov 2003
TL;DR: In this paper, a review of the different types and applications of photonic crystal fibers with particular emphasis on recent advances in the field is presented, with a focus on the photonic bandgap effect.
Abstract: Photonic crystal fibers having a complex microstructure in the transverse plane constitute a new and promising class of optical fibers. Such fibers can either guide light through total internal reflection or the photonic bandgap effect, In this paper, we review the different types and applications of photonic crystal fibers with particular emphasis on recent advances in the field.
403 citations
TL;DR: It is argued that the multimode cutoff occurs at a wavelength lambda* that satisfies VPCF(lambda*) = pi, and by comparing this approach with numerics and recent cutoff calculations, this result is confirmed.
Abstract: We address the long-standing unresolved problem concerning the V parameter in a photonic crystal fiber. In formulating the parameter appropriate for a core defect in a periodic structure, we argue that the multimode cutoff occurs at a wavelength lambda* that satisfies VPCF(lambda*) = pi. By comparing this approach with numerics and recent cutoff calculations we confirm this result.
274 citations
TL;DR: A new fiber design comprising a hybrid core-region with three-fold symmetry that enables unprecedented dispersion control while maintaining low loss and a high nonlinear coefficient is proposed.
Abstract: Photonic crystal fibers are highly attractive as nonlinear media as they combine a large nonlinear coefficient and a highly customizable zero dispersion wavelength - flexibility not found in any other medium. However, the high dispersion slope at the zero-dispersion wavelength demonstrated so far is very limiting to the useful bandwidth. We propose a new fiber design comprising a hybrid core-region with three-fold symmetry that enables unprecedented dispersion control while maintaining low loss and a high nonlinear coefficient. The lowest dispersion slope obtained is 1·10-3ps/(km·nm2) or one order of magnitude lower than for conventional slope reduced nonlinear fibers. The nonlinear coefficient is more than 11 (W·km)-1 and loss below 7.9 dB/km at 1.55 µm has been achieved.
245 citations
Patent•
14 Mar 2003
TL;DR: An optical fiber having a longitudinal direction and a cross-section perpendicular thereto, said fiber in a cross section comprising: (a) a core region (11) having a refractive index profile with the highest as discussed by the authors nc, and (b) a cladding region comprising cladding features having a center-to-center spacing, Λ, and a diameter, d, of around 0.4Λ or larger, wherein nc and d are adapted such that the fiber exhibits zero dispersion wavelength of a fundamental mode in the wavelength range from 1530 nm to 1640
Abstract: An optical fiber having a longitudinal direction and a cross-section perpendicular thereto, said fiber in a cross-section comprising: (a) a core region (11) having a refractive index profile with a highest refractive index nc, and (b) a cladding region comprising cladding features (10) having a center-to-center spacing, Λ, and a diameter, d, of around 0.4Λ or larger, wherein nc, Λ and d are adapted such that the fiber exhibits zero dispersion wavelength of a fundamental mode in the wavelength range from 1530 nm to 1640 nm; a method of producing such a fiber; and use of such an optical fiber in e.g. an optical communication system, in an optical fiber laser, in an optical fiber amplifier, in an optical fiber Raman amplifier, in a dispersion compensator, in a dispersion and/or dispersion slope compensator.
167 citations
TL;DR: The growth and enzyme production by Trichoderma reesei Rut C-30 using different lignocellulosic materials as carbon source were investigated and it was found that endoglucanase and endoxylanse activities were produced throughout the cultivations, whereas α-arabinosidase was induced late during the cultivation.
157 citations
TL;DR: All-fiber chirped pulse amplification using an air-core photonic bandgap fiber is shown, for the first time to the authors' knowledge, and can potentially be used to obtain ultra-high pulse peak powers.
Abstract: We show, for the first time to our knowledge, all-fiber chirped pulse amplification using an air-core photonic bandgap fiber. Pulses from a wavelength- and duration-tunable femtosecond/picosecond source at 10 GHz were dispersed in 100 m of dispersion compensating fiber before being amplified in an erbium-doped fiber amplifier and subsequently recompressed in 10 m of the anomalously dispersive photonic bandgap fiber. Pulses as short as 1.1 ps were obtained. As air-core fibers present negligible nonlinearity, the presented configuration can potentially be used to obtain ultra-high pulse peak powers. A study of the air-core fiber dispersion and dispersion slope is also presented.
126 citations
TL;DR: In this article, the femto and picosecond pulses delivered by the amplifier are coupled into two different photonic crystal fibers and obtained the highest output power of 5 W with a spectrum ranging from below 500 nm up to above 1800 nm.
124 citations
23 Mar 2003
TL;DR: In this article, the authors demonstrate the first nonlinear fiber where both dispersion level and slope can be fully controlled in a broad wavelength range while maintaining low loss and a high nonlinear coefficient.
Abstract: We demonstrate the first nonlinear fiber where both dispersion level and slope can be fully controlled in a broad wavelength range while maintaining low loss and a high nonlinear coefficient. Lowest slope obtained is l.10/sup -3/ps/(km.nm/sup 2/).
56 citations
TL;DR: The cutoff is measured for seven different fiber geometries with different pitches and relative hole sizes, and very good agreement with recent theoretical work is found.
Abstract: Modal cutoff is investigated experimentally in a series of high-quality nonlinear photonic crystal fibers. We demonstrate a suitable measurement technique with which to determine the cutoff wavelength and verify the technique by inspecting the near field of the modes that may be excited below and above the cutoff. We observe a double-peak structure in the cutoff spectra, which is attributed to splitting of the higher-order modes. The cutoff is measured for seven different fiber geometries with different pitches and relative hole sizes, and very good agreement with recent theoretical work is found.
53 citations
TL;DR: In this paper, a 50m-long photonic crystal fiber with zero-dispersion wavelength at 1552 nm is used as the nonlinear medium in a nonlinear optical loop-mirror-based demultiplexer.
Abstract: A 50-m-long photonic crystal fiber with zero-dispersion wavelength at 1552 nm is used as the nonlinear medium in a nonlinear optical loop-mirror-based demultiplexer. The successful demultiplexing of an 80-Gb/s optical time-division multiplexing signal transmitted through an 80-km span of standard single-mode fiber and the error-free demultiplexing from 160 Gb/s are achieved.
46 citations
TL;DR: In this article, the authors demonstrated the transmission at 40 Gbit/s over large mode area photonic crystal fiber (PCF) together with dispersion compensation by optical phase conjugation in a highly nonlinear PCF.
Abstract: Transmission at 40 Gbit/s over large mode area photonic crystal fibre (PCF) together with dispersion compensation by optical phase conjugation in a highly nonlinear PCF are demonstrated for the first time
TL;DR: In this paper, the fundamental physical mechanisms determining the dispersion properties of optical crystal fibers guiding by either total internal reflection or photonic bandgap effects are discussed, and a number of examples from recent modeling and experimental work serve to illustrate their general conclusions.
Abstract: The dispersion, which expresses the variation with wavelength of the guided-mode group velocity, is one of the most important properties of optical fibers. Photonic crystal fibers (PCFs) offer much larger flexibility than conventional fibers with respect to tailoring of the dispersion curve. This is partly due to the large refractive-index contrast available in silica/air microstructures, and partly due to the possibility of making complex refractive-index structures over the fiber cross section. We discuss the fundamental physical mechanisms determining the dispersion properties of PCFs guiding by either total internal reflection or photonic bandgap effects, and use these insights to outline design principles and generic behaviours of various types of PCFs. A number of examples from recent modeling and experimental work serve to illustrate our general conclusions.
TL;DR: In this paper, the authors measured the Raman gain efficiency of a 2.3 /spl mu/m-core-diameter holey fiber using three different techniques and showed that the high efficiency is due to small mode-field diameter of the holey fibre, as expected.
Abstract: The Raman gain efficiency of a 2.3 /spl mu/m-core-diameter holey fibre was measured using three different techniques. A /spl sim/4.65/spl times/10/sup -3/ W/sup -1/ m/sup -1/ efficiency is obtained by all techniques with mismatches lying within the estimated errors. It is shown that the high efficiency is due to small mode-field diameter of the holey fibre, as expected. The use of the fibre as a continuous-wave-pumped Raman amplifier is discussed.
Proceedings Article•
01 Jan 2003
23 Mar 2003
TL;DR: In this article, a range of novel properties of the new generation of highly nonlinear photonic crystal fibers with zero dispersion near 1.55 /spl mu/m were reported.
Abstract: We report on a range of novel properties of the new generation of highly nonlinear photonic crystal fibers with zero dispersion near 1.55 /spl mu/m. Aspects of loss mechanisms, dispersion properties and birefringence tailoring are described.
29 Jun 2003
TL;DR: In this paper, a photonic crystal fiber (PCF) was used for supercontinuum (SC) generation at 1550 nm with pulse widths of 0.3 to 2.5 ps. Subsequent bandpass filtering of the generated SC spectrum enables the realisation of an optical clock frequency translator continuously tunable up to the L-band.
Abstract: Supercontinuum (SC) generation is demonstrated in a photonic crystal fibre (PCF) at 1550 nm with pulse widths of 0.3 to 2.5 ps. Subsequent band-pass filtering of the generated SC spectrum enables the realisation of an optical clock frequency translator continuously tunable up to the L-band.
Patent•
14 Mar 2003
TL;DR: An optical fiber having a longitudinal direction and a cross-section perpendicular to the longitudinal direction is considered in this paper, where the authors propose a method of pro-ducing such a fiber; and use of such an optical fibre in e.g. an optical communication system, in an optical fiber laser, in optical fibre amplifier, in a optical fibre Raman amplifier, and in a dispersion compensator, in dis-persion and/or dispersion slope compensator.
Abstract: An optical fibre having a longitudinal direction and a cross-section perpendicular thereto, said fibre in a cross-section comprising: (a) a core region (11) having a refractive index profile with a highest refractive index nc, and (b) a cladding region comprising cladding features (10) having a centre-to-centre spacing, Λ, and a diameter, d, of around 0.4Λ or larger, wherein nc, Λ and d are adapted such that the fibre exhibits zero dispersion wavelength of a fundamental mode in the wavelength range from 1530 nm to 1640 nm; a method of producing such a fibre; and use of such an optical fibre in e.g. an optical communication system, in an optical fibre laser, in an optical fibre amplifier, in an optical fibre Raman amplifier, in a dispersion compensator, in a dispersion and/or dispersion slope compensator.
Proceedings Article•
01 Jun 2003
Proceedings Article•
06 Jun 2003
TL;DR: In this article, the first 40 Gbps transmission at 40 Gbit/s over large mode area photonic crystal fiber (PCF) with dispersion compensation by optical phase conjugation in a highly nonlinear PCF was demonstrated.
Abstract: Transmission at 40 Gbit/s over large mode area photonic crystal fiber (PCF) together with dispersion compensation by optical phase conjugation in a highly nonlinear PCF are demonstrated for the first time.
Proceedings Article•
06 Jun 200302 Feb 2003
TL;DR: In this paper, the authors report on the 5 W average power, supercontinuum generation in different air-silica microstructered fibers using a compact largemode-area ytterbium-doped femtosecond fiber amplifier at 1060 nm center wavelength as the excitation source.
Abstract: We report on the 5 W average power, supercontinuum generation in different air-silica microstructered fibers using a compact large-mode-area ytterbium-doped femtosecond fiber amplifier at 1060 nm center wavelength as the excitation source. The flat continuum ranges from 1800 nm. The experimental results are confirmed by numerical simulations, revealing the evolution and fission of higher order solitons as the main contribution to the continuum.