Showing papers on "Photonic-crystal fiber published in 2011"
TL;DR: It is shown that HC MOFs with the cladding consisting only of one row of silica capillaries allows to guide light from the near to mid infrared despite of high material losses ofsilica in this spectral region.
Abstract: We present a numerical and experimental demonstration of a waveguide regime in a broad band spectral range for the hollow core microstructured optical fibers (HC MOFs) made of silica with a negative curvature of the core boundary. It is shown that HC MOFs with the cladding consisting only of one row of silica capillaries allows to guide light from the near to mid infrared despite of high material losses of silica in this spectral region. Such result can be obtained by a special arrangement of cladding capillaries which leads to a change in the sign of the core boundary curvature. The change in the sign of the core boundary curvature leads to a loss of simplicity of boundary conditions for core modes and to "localization" and limitation of their interaction with the cladding material in space. Such HC MOFs made of different materials can be potential candidates for solving problem of ultra high power transmission including transmission of CO and CO2 laser radiation.
396 citations
TL;DR: The fabrication of a seven-cell-core and three-ring-cladding large-pitch Kagome-lattice hollow-core photonic crystal fiber with a hypocycloid-shaped core structure with potential for a number of applications in which the combination of a large optical bandwidth and a low loss is a prerequisite.
Abstract: We report on the fabrication of a seven-cell-core and three-ring-cladding large-pitch Kagome-lattice hollow-core photonic crystal fiber (HC-PCF) with a hypocycloid-shaped core structure. We demonstrate experimentally and theoretically that the design of this core shape enhances the coupling inhibition between the core and cladding modes and offers optical attenuation with a baseline of ∼180 dB/km over a transmission bandwidth larger than 200 THz. This loss figure rivals the state-of-the-art photonic bandgap HC-PCF while offering an approximately three times larger bandwidth and larger mode areas. Also, it beats the conventional circular-core-shaped Kagome HC-PCF in terms of the loss. The development of this novel (to our knowledge) HC-PCF has potential for a number of applications in which the combination of a large optical bandwidth and a low loss is a prerequisite.
390 citations
TL;DR: In this article, the use of hollow-core photonic crystal fibers (PCFs) in the field of ultrafast gas-based nonlinear optics, including recent experiments, numerical modeling, and a discussion of future prospects, is discussed.
Abstract: We review the use of hollow-core photonic crystal fibers (PCFs) in the field of ultrafast gas-based nonlinear optics, including recent experiments, numerical modeling, and a discussion of future prospects. Concentrating on broadband guiding kagome-style hollow-core PCF, we describe its potential for moving conventional nonlinear fiber optics both into extreme regimes—such as few-cycle pulse compression and efficient deep ultraviolet wavelength generation—and into regimes hitherto inaccessible, such as single-mode guidance in a photoionized plasma and high-harmonic generation in fiber.
338 citations
TL;DR: It is shown that using this approach one can generate an arbitrary output optical field within the accessible field of view and range of spatial frequencies given by fibre core diameter and numerical aperture, respectively, that contains over 80% of the total available power.
Abstract: We present a powerful approach towards full understanding of laser light propagation through multimode optical fibres and control of the light at the fibre output. Transmission of light within a multimode fibre introduces randomization of laser beam amplitude, phase and polarization. We discuss the importance of each of these factors and introduce an experimental geometry allowing full analysis of the light transmission through the multimode fibre and subsequent beam-shaping using a single spatial light modulator. We show that using this approach one can generate an arbitrary output optical field within the accessible field of view and range of spatial frequencies given by fibre core diameter and numerical aperture, respectively, that contains over 80% of the total available power. We also show that this technology has applications in biophotonics. As an example, we demonstrate the manipulation of colloidal microparticles.
333 citations
TL;DR: Through simulations, it is shown that the proposed coupled multi-core fiber allows lower modal dependent loss, mode coupling and differential modal group delay than few-mode fibers, and could be a good candidate for both spatial division multiplexing and single-mode operation.
Abstract: In this paper, the concept of supermode is introduced for long-distance optical transmission systems. The supermodes exploit coupling between the cores of a multi-core fiber, in which the core-to-core distance is much shorter than that in conventional multi-core fiber. The use of supermodes leads to a larger mode effective area and higher mode density than the conventional multi-core fiber. Through simulations, we show that the proposed coupled multi-core fiber allows lower modal dependent loss, mode coupling and differential modal group delay than few-mode fibers. These properties suggest that the coupled multi-core fiber could be a good candidate for both spatial division multiplexing and single-mode operation.
316 citations
Patent•
03 Aug 2011
TL;DR: Disclosed is an optical transmission fiber having reduced bending and micro-bending losses that is commercially usable in FTTH or FTTC transmission systems as mentioned in this paper, but it is not suitable for FTTH systems.
Abstract: Disclosed is an optical transmission fiber having reduced bending and microbending losses that is commercially usable in FTTH or FTTC transmission systems.
275 citations
TL;DR: The first detailed demonstrations of octave-spanning SC generation in all-normal dispersion photonic crystal fibers (ANDi PCF) in the visible and near-infrared spectral regions are presented, presenting the broadest spectra generated in the normal dispersion regime of an optical fiber.
Abstract: We present the first detailed demonstrations of octave-spanning SC generation in all-normal dispersion photonic crystal fibers (ANDi PCF) in the visible and near-infrared spectral regions. The resulting spectral profiles are extremely flat without significant fine structure and with excellent stability and coherence properties. The key benefit of SC generation in ANDi PCF is the conservation of a single ultrashort pulse in the time domain with smooth and recompressible phase distribution. For the first time we confirm the exceptional temporal properties of the generated SC pulses experimentally and demonstrate their applicability in ultrafast transient absorption spectroscopy. The experimental results are in excellent agreement with numerical simulations, which are used to illustrate the SC generation dynamics by self-phase modulation and optical wave breaking. To our knowledge, we present the broadest spectra generated in the normal dispersion regime of an optical fiber.
266 citations
TL;DR: An enhanced evanescent field fiber refractometer based on a tapered multimode fiber sandwiched between two single-mode fibers offers ultrahigh sensitivity and is the highest value reported to date (to the authors' knowledge) in the literature.
Abstract: We propose and experimentally demonstrate an enhanced evanescent field fiber refractometer based on a tapered multimode fiber sandwiched between two single-mode fibers Experiments show that this fiber sensor offers ultrahigh sensitivity [better than 1900nm/RIU at a refractive index (RI) of 144] for RI measurements within the range of 133 to 144, in agreement with the theoretical predictions This is the highest value reported to date (to our knowledge) in the literature
260 citations
TL;DR: A compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled high-birefringence photonic crystal fiber (PCF) is proposed and experimentally demonstrated.
Abstract: A compact temperature sensor based on a fiber loop mirror (FLM) combined with an alcohol-filled high-birefringence photonic crystal fiber (PCF) is proposed and experimentally demonstrated. The output of the FLM is an interference spectrum with many resonant dips, of which the wavelengths are quite sensitive to the change of the refractive index of the filled alcohol for the interference of the FLM. Simulation analysis predicts a high temperature sensitivity, and experimental results show it reaches up to 6.6 nm/°C for the 6.1-cm-long PCF used in the FLM.
247 citations
TL;DR: Low-loss guidance combined with the core isolated from environmental perturbations make these all-dielectric fibers suitable for practical terahertz imaging and sensing applications.
Abstract: In this work we report two designs of subwavelength fibers packaged for practical terahertz wave guiding. We describe fabrication, modeling and characterization of microstructured polymer fibers featuring a subwavelength-size core suspended in the middle of a large porous outer cladding. This design allows convenient handling of the subwavelength fibers without distorting their modal profile. Additionally, the air-tight porous cladding serves as a natural enclosure for the fiber core, thus avoiding the need for a bulky external enclosure for humidity-purged atmosphere. Fibers of 5 mm and 3 mm in outer diameters with a 150 µm suspended solid core and a 900 µm suspended porous core respectively, were obtained by utilizing a combination of drilling and stacking techniques. Characterization of the fiber optical properties and the subwavelength imaging of the guided modes were performed using a terahertz near-field microscopy setup. Near-field imaging of the modal profiles at the fiber output confirmed the effectively single-mode behavior of such waveguides. The suspended core fibers exhibit transmission from 0.10 THz to 0.27 THz (larger core), and from 0.25 THz to 0.51 THz (smaller core). Due to the large fraction of power that is guided in the holey cladding, fiber propagation losses as low as 0.02 cm(-1) are demonstrated specifically for the small core fiber. Low-loss guidance combined with the core isolated from environmental perturbations make these all-dielectric fibers suitable for practical terahertz imaging and sensing applications.
226 citations
TL;DR: In this paper, a simple method for the in-situ monitoring of the deposition of few-layers graphene in an optical fiber end by mechanical exfoliation is presented.
Abstract: Graphene exhibits wavelength-independent, saturable optical absorption with fast response time, and large modulation depth. Thus, it is an attractive material for the saturable absorption of fiber lasers. In this paper, we report a simple method for the in-situ monitoring of the deposition of few-layers graphene in an optical fiber end by mechanical exfoliation. Saturable absorbers with different number of graphene layers (from 4 layers of graphene to few 10 s of layers) are prepared and low threshold, self-starting passive mode-locked operation of a fiber laser with sub-picosecond pulse duration is demonstrated.
TL;DR: A novel liquid level sensor based on multimode interference (MMI) effects is proposed and demonstrated that exhibits a highly linear response with the sensing range and multiplexed operations easily controlled by just modifying the length of the no-core fiber.
Abstract: A novel (to the best of our knowledge) liquid level sensor based on multimode interference (MMI) effects is proposed and demonstrated. By using a multimode fiber (MMF) without cladding, known as no-core fiber, liquids around the MMF modify the self-imaging properties of the MMI device and the liquid level can be detected. We show that the sensor exhibits a highly linear response with the sensing range and multiplexed operations easily controlled by just modifying the length of the no-core fiber. At the same time, we can measure the refractive index of the liquid based on the maximum peak wavelength shift. We can also use the sensor for continuous and discrete liquid level sensing applications, thus providing a liquid level sensor that is inexpensive with a very simple fabrication process.
TL;DR: In this article, the authors presented a random fiber laser that is tunable over a broad wavelength range with uniquely flat output power and high efficiency, which outperforms traditional lasers of the same category.
Abstract: An optical fiber is treated as a natural one-dimensional random system where lasing is possible due to a combination of Rayleigh scattering by refractive index inhomogeneities and distributed amplification through the Raman effect. We present such a random fiber laser that is tunable over a broad wavelength range with uniquely flat output power and high efficiency, which outperforms traditional lasers of the same category. Outstanding characteristics defined by deep underlying physics and the simplicity of the scheme make the demonstrated laser a very attractive light source both for fundamental science and practical applications.
TL;DR: It is demonstrated that the supercontinuum is compressible to a duration of 26 fs, and has a high degree of coherence between all the frequency components, and is a single pulse in the time domain.
Abstract: We demonstrate supercontinuum generation in a photonic crystal fiber with all-normal group velocity dispersion. Pumping a short section of this fiber with compressed pulses from a compact amplified fiber laser generates a 200 nm bandwidth continuum with typical self-phase-modulation characteristics. We demonstrate that the supercontinuum is compressible to a duration of 26 fs. It therefore has a high degree of coherence between all the frequency components, and is a single pulse in the time domain. A smooth, flat spectrum spanning 800 nm is achieved using a longer piece of fiber.
TL;DR: In this paper, the optical guidance properties of hollow-core photonic crystal fibers are reviewed and modal properties of these fibers and the transmission loss mechanisms in photonic bandgap and inhibited coupling guidance are assessed.
Abstract: We review the optical guidance properties of hollow-core photonic crystal fibers. We follow a historical perspective to introduce the two major optical guidance mechanisms that were identified as operating in these fibers: photonic bandgap guidance and inhibited coupling guidance. We then review the modal properties of these fibers and assess the transmission loss mechanisms in photonic bandgap guiding hollow-core photonic crystal fiber. We dedicate a section to a review of the technical basics of hollow-core photonic crystal fiber fabrication and photonic microcell assembly. We review some of the early results on the use of hollow-core photonic crystal fiber for laser guiding micro-sized particles, as well as the generation of stimulated Raman scattering, electromagnetically induced transparency and laser frequency stabilization when the fiber core is filled with a gas-phase material. We conclude this review with a non-exhaustive list of prospects where hollow-core photonic crystal fiber could play a cen...
TL;DR: According to the model presented in this paper, the most likely cause for the beam quality degradation is an inversion-induced grating created by the interplay between modal interference along the fiber and transversal hole burning.
Abstract: Recent work on high-power fiber amplifiers report on a degradation of the output beam quality or even on the appearance of mode instabilities. By combining the transversally resolved rate equations with a 3D Beam propagation method we have managed to create a model able to provide an explanation of what we believe is at the root of this effect. Even though this beam quality degradation is conventionally linked to transversal hole burning, our simulations show that this alone cannot explain the effect in very large mode area fibers. According to the model presented in this paper, the most likely cause for the beam quality degradation is an inversion-induced grating created by the interplay between modal interference along the fiber and transversal hole burning.
TL;DR: The spectral broadening of ~1 μJ 30 fs pulses propagating in an Ar-filled hollow-core photonic crystal fiber results in efficient emission of dispersive waves in the deep-UV region.
Abstract: We report on the spectral broadening of ~1 μJ 30 fs pulses propagating in an Ar-filled hollow-core photonic crystal fiber. In contrast with supercontinuum generation in a solid-core photonic crystal fiber, the absence of Raman and unique pressure-controlled dispersion results in efficient emission of dispersive waves in the deep-UV region. The UV light emerges in the single-lobed fundamental mode and is tunable from 200 to 320 nm by varying the pulse energy and gas pressure. The setup is extremely simple, involving <1 m of a gas-filled photonic crystal fiber, and the UV signal is stable and bright, with experimental IR to deep-UV conversion efficiencies as high as 8%. The source is of immediate interest in applications demanding high spatial coherence, such as laser lithography or confocal microscopy.
TL;DR: A high-temperature sensor based on a Mach-Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed and fabricated by concatenating two microcavities separated by a middle section.
Abstract: A high-temperature sensor based on a Mach–Zehnder interferometer (MZI) in a conventional single-mode optical fiber is proposed and fabricated by concatenating two microcavities separated by a middle section A femtosecond laser is used to fabricate a microhole on the center of a fiber end Then a micro-air-cavity is formed by splicing the microholed fiber end with a normal fiber end The interferometer is applied for high-temperature sensing, in the range of 500–1200 °C, with a sensitivity of 109 pm/°C that, to the best of our knowledge, is highest in silica fiber temperature sensors Also, the interferometer is insensitive to external refractive index (RI), which is desirable for temperature sensors
TL;DR: A novel splicing-based pressure-assisted melt-filling technique for creating metallic nanowires in hollow channels in microstructured silica fibers that suggest applications in fields such as nonlinear plasmonics, near-field scanning optical microscope tips, cylindrical polarizers, optical sensing and telecommunications.
Abstract: We report a novel splicing-based pressure-assisted melt-filling technique for creating metallic nanowires in hollow channels in microstructured silica fibers Wires with diameters as small as 120 nm (typical aspect ration 50:1) could be realized at a filling pressure of 300 bar As an example we investigate a conventional single-mode step-index fiber with a parallel gold nanowire (wire diameter 510 nm) running next to the core Optical transmission spectra show dips at wavelengths where guided surface plasmon modes on the nanowire phase match to the glass core mode By monitoring the side-scattered light at narrow breaks in the nanowire, the loss could be estimated Values as low as 07 dB/mm were measured at resonance, corresponding to those of an ultra-long-range eigenmode of the glass-core/nanowire system By thermal treatment the hollow channel could be collapsed controllably, permitting creation of a conical gold nanowire, the optical properties of which could be monitored by side-scattering The reproducibility of the technique and the high optical quality of the wires suggest applications in fields such as nonlinear plasmonics, near-field scanning optical microscope tips, cylindrical polarizers, optical sensing and telecommunications
TL;DR: A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber, which makes it very attractive for high-pressure and high-temperature sensing applications.
Abstract: A fiber-optic Fabry-Perot interferometer was constructed by splicing a short length of photonic crystal fiber to a standard single-mode fiber. The photonic crystal fiber functions as a Fabry-Perot cavity and serves as a direct sensing probe without any additional components. Its pressure and temperature responses in the range of 0-40 MPa and 25°C-700°C were experimentally studied. The proposed sensor is easy to fabricate, potentially low-cost, and compact in size, which makes it very attractive for high-pressure and high-temperature sensing applications.
TL;DR: The incoherent beam combination of the four narrow-linewidth fiber amplifier chains running at different wavelengths using a polarization-independent dielectric reflective diffraction grating mainly preserving the beam quality of the individual fiber amplifiers.
Abstract: We report on the incoherent beam combination of the four narrow-linewidth fiber amplifier chains running at different wavelengths Each main amplifier stage consists of a large-mode-area photonic crystal fiber delivering more than 2 kW of optical power The four output beams are spectrally combined to a single beam with an output power of 82 kW using a polarization-independent dielectric reflective diffraction grating mainly preserving the beam quality of the individual fiber amplifiers
TL;DR: In this article, a magnetic field sensor combining photonic crystal fiber and optofluidics was presented. But they used a single platform by infiltrating a small amount of Fe3O4 magnetic optorluid/nanofluide in cladding holes of polarization-maintaining photonic fiber.
Abstract: We report a magnetic field sensor having advantages of both photonic crystal fiber and optofluidics, combining them on a single platform by infiltrating small amount of Fe3O4 magnetic optofluid/nanofluid in cladding holes of polarization-maintaining photonic crystal fiber We demonstrated that magnetic field of few mT can be easily and very well detected with higher sensitivity of 242 pm/mT The change in the birefringence values has been correlated to the response of nanofluid to applied field
TL;DR: The detection of the proteins lysozyme and cytochrome c as well as the live bacterial cells of Shewanella oneidensis MR-1 in aqueous solutions with sensitivities order(s) of magnitude higher than those previously reported are reported.
Abstract: We report the detection of the proteins lysozyme and cytochrome c as well as the live bacterial cells of Shewanella oneidensis MR-1 in aqueous solutions with sensitivities order(s) of magnitude higher than those previously reported. Two highly sensitive surface-enhanced Raman scattering (SERS)-based biosensors using optical fibers have been employed for such label-free macromolecule detections. The first sensor is based on a tip-coated multimode fiber (TCMMF) with a double-substrate “sandwich” structure, and a detection limit of 0.2 μg/mL is achieved in protein detections. The second sensor is based on a liquid core photonic crystal fiber (LCPCF) with a better confinement of light inside the fiber core, and a detection limit of 106 cells/mL is achieved for the bacteria detection. Both SERS biosensors show great potential for highly sensitive and molecule-specific detection and identification of biomolecules.
TL;DR: 3-dimensional luminescence spectra (luminescence intensity as a function of the excitation and emission wavelengths) have been obtained for bismuth-doped optical fibers of various compositions in a wide spectral range (450-1700 nm).
Abstract: For the first time, 3-dimensional luminescence spectra (luminescence intensity as a function of the excitation and emission wavelengths) have been obtained for bismuth-doped optical fibers of various compositions in a wide spectral range (450-1700 nm). The bismuth-doped fibers investigated have the following core compositions: SiO2, GeO2, Al-doped SiO2, and P-doped SiO2. The measurements are performed at room and liquid nitrogen temperatures. Based on the experimental results, the positions of the low-lying energy-levels of the IR bismuth active centers in SiO2- and GeO2-core fibers have been determined. Similarity of the energy-level schemes for the two core compositions has been revealed.
TL;DR: A nanosecond-pulse erbium-doped fiber laser that is passively mode locked by a hollow-core photonic crystal fiber filled with few-layered graphene oxide solution is demonstrated, providing a simple and efficient approach to integrate the graphene into the optical fiber system.
Abstract: We demonstrate a nanosecond-pulse erbium-doped fiber laser that is passively mode locked by a hollow-core photonic crystal fiber filled with few-layered graphene oxide solution. Owing to the good solution processing capability of few-layered graphene oxide, which can be filled into the core of a hollow-core photonic crystal fiber through a selective hole filling process, a graphene saturable absorber can be successfully fabricated. The output pulses obtained have a center wavelength, pulse width, and repetition rate of 1561.2 nm, 4.85 ns, and 7.68 MHz, respectively. This method provides a simple and efficient approach to integrate the graphene into the optical fiber system.
TL;DR: By using a gas-filled kagome-style photonic crystal fiber, nonlinear fiber optics is studied in the regime of optically induced ionization and suggests free-electron densities of ∼10(17) cm(-3) are achieved at peak intensities of 10(14) W/cm(2) over length scales of several centimeters.
Abstract: By using a gas-filled kagome-style photonic crystal fiber, nonlinear fiber optics is studied in the regime of optically induced ionization. The fiber offers low anomalous dispersion over a broad bandwidth and low loss. Sequences of blueshifted pulses are emitted when 65 fs, few-microjoule pulses, corresponding to high-order solitons, are launched into the fiber and undergo self-compression. The experimental results are confirmed by numerical simulations which suggest that free-electron densities of ∼10(17) cm(-3) are achieved at peak intensities of 10(14) W/cm(2) over length scales of several centimeters.
TL;DR: A fiber Mach-Zehnder interferometer sensor based on a single "S"-like fiber taper has been fabricated via applying nonaxial pull in fiber tapering by a fusion splicer, which has a refractive index sensitivity 30 times higher than that of the normal two-taper-based MZI sensors.
Abstract: A fiber Mach–Zehnder interferometer (MZI) sensor, novel to our knowledge, based on a single “S”-like fiber taper has been fabricated via applying nonaxial pull in fiber tapering by a fusion splicer. The typical feature size of the structure has a length of 660 μm and the axial offset of 96 μm. This S fiber taper MZI has a refractive index (RI) sensitivity of 1590 nm/refractive index unit in the RI range of 1.409–1.425 and a strain sensitivity of about −60 pm/microstrain, which is 30 times higher than that of the normal two-taper-based MZI sensors.
TL;DR: In this paper, the authors review the work on efficient interfaces between a silicon-on-insulator photonic IC and a single-mode optical fiber based on grating structures and present several device configurations that provide high efficiency, polarization insensitive, and broadband optical coupling on a small footprint.
Abstract: In this paper, we review our work on efficient interfaces between a silicon-on-insulator photonic IC and a single-mode optical fiber based on grating structures. Several device configurations are presented that provide high efficiency, polarization insensitive, and broadband optical coupling on a small footprint. The high alignment tolerance and the fact that the optical fiber interface is out-of-plane provide opportunities for easy packaging and wafer-scale testing of the photonic IC. Finally, an optical probe based on a grating structure defined on the fiber facet is described.
TL;DR: A highly sensitive refractive index (RI) sensor based on three cascaded single-mode fiber tapers, in which a weak taper is sandwiched between the two tapers to improve the sensitivity of the sensor.
Abstract: We report a highly sensitive refractive index (RI) sensor based on three cascaded single-mode fiber tapers, in which a weak taper is sandwiched between the two tapers to improve the sensitivity of the sensor. Experimental results show that the sensitivity of the device is 0.286 nm for a 0.01 RI change, which is about four times higher than that of the normal two-cascaded-taper-based Mach–Zehnder interferometer. In addition, the sensitivity of the device could be enhanced by tapering a longer and thinner middle weak taper. Such kinds of low-cost and highly sensitive fiber-optic RI sensors would find applications in chemical or biochemical sensing fields.
TL;DR: The pressure-assisted melt-filling approach makes it possible to realize highly nonlinear devices with unusual combinations of materials, and it is shown numerically that a 1 cm long As2S3:silica step-index fiber with a core diameter of 1 µm, pumped by 60 fs pulses at 1550 nm, would generate a broadband supercontinuum out to 4 µm.
Abstract: We explore the use of a highly nonlinear chalcogenide-silica waveguide for supercontinuum generation in the near infrared. The structure was fabricated by a pressure-assisted melt-filling of a silica capillary fiber (1.6 µm bore diameter) with Ga4Ge21Sb10S65 glass. It was designed to have zero group velocity dispersion (for HE11 core mode) at 1550 nm. Pumping a 1 cm length with 60 fs pulses from an erbium-doped fiber laser results in the generation of octave-spanning supercontinuum light for pulse energies of only 60 pJ. Good agreement is obtained between the experimental results and theoretical predictions based on numerical solutions of the generalized nonlinear Schrodinger equation. The pressure-assisted melt-filling approach makes it possible to realize highly nonlinear devices with unusual combinations of materials. For example, we show numerically that a 1 cm long As2S3:silica step-index fiber with a core diameter of 1 µm, pumped by 60 fs pulses at 1550 nm, would generate a broadband supercontinuum out to 4 µm.