Showing papers by "P. St. J. Russell published in 2000"
TL;DR: The frequency comb generated by a femtosecond mode-locked laser is used and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region.
Abstract: We have used the frequency comb generated by a femtosecond mode-locked laser and broadened to more than an optical octave in a photonic crystal fiber to realize a frequency chain that links a 10 MHz radio frequency reference phase-coherently in one step to the optical region. By comparison with a similar frequency chain we set an upper limit for the uncertainty of this new approach to 5. 1x10(-16). This opens the door for measurement and synthesis of virtually any optical frequency and is ready to revolutionize frequency metrology.
1,136 citations
TL;DR: Based on spectral measurements of the polarization mode beating, it is estimated that the strongly anisotropic photonic crystal fiber has a beat length of approximately 0.4 mm at a wavelength of 1540 nm, in good agreement with the results of modeling.
Abstract: We report a strongly anisotropic photonic crystal fiber. Twofold rotational symmetry was introduced into a single-mode fiber structure by creation of a regular array of airholes of two sizes disposed about a pure-silica core. Based on spectral measurements of the polarization mode beating, we estimate that the fiber has a beat length of approximately 0.4 mm at a wavelength of 1540 nm, in good agreement with the results of modeling.
860 citations
TL;DR: In this paper, a supercontinuum light with a spectrum more than two octaves broad (370-1545 nm at the 20-dB level) was generated in a standard telecommunications fiber by femtosecond pulses from an unamplified Ti:sapphire laser.
Abstract: Supercontinuum light with a spectrum more than two octaves broad (370–1545 nm at the 20-dB level) was generated in a standard telecommunications fiber by femtosecond pulses from an unamplified Ti:sapphire laser. The fiber had been tapered to a diameter of ∼2 µm over a 90-mm length. The pulse energy was 3.9 nJ (average power, 300 mW). This source of high-intensity single-mode white light should find widespread applications in frequency metrology and spectroscopy, especially since no unconventional fibers are needed.
711 citations
TL;DR: In this paper, the authors describe the measured group-velocity dispersion characteristics of several air-silica photonic crystal fibers with anomalous group velocity dispersion at visible and near-infrared wavelengths.
Abstract: We describe the measured group-velocity dispersion characteristics of several air-silica photonic crystal fibers with anomalous group-velocity dispersion at visible and near-infrared wavelengths. The values measured over a broad spectral range are compared to those predicted for an isolated strand of silica surrounded by air. We demonstrate a strictly single-mode fiber which has zero dispersion at a wavelength of 700 mm. These fibers are significant for the generation of solitons and supercontinua using ultrashort pulse sources.
683 citations
TL;DR: Soliton effects are observed at 850 nm in a pure silica photonic crystal fiber with group velocity dispersion (GVD) characteristics unattainable in conventional fibre as mentioned in this paper. But this is not the case in the case of optical fiber.
Abstract: Soliton effects are observed at 850 nm in a pure silica photonic crystal fibre with group velocity dispersion (GVD) characteristics unattainable in conventional fibre. Zero GVD is obtained at 740 nm.
183 citations
TL;DR: In this article, an ytterbium doped core has been incorporated into a photonic crystal fiber (PCF) with anomalous group velocity dispersion at all wavelengths longer than 730 nm.
Abstract: An ytterbium doped core has been incorporated into a photonic crystal fibre (PCF) with anomalous group velocity dispersion at all wavelengths longer than 730 nm. Laser action is observed for the first time in such a fibre. This demonstration of lasing in PCF is a vital step towards realising the huge potential of PCF for fibre laser applications.
136 citations
TL;DR: In this paper, a three-core photonic crystal fiber is used to measure deformation of a bridge undergoing loading trials using interferometric interrogation at a single wavelength and the ability of the fiber sensor to measure bend in two dimensions is demonstrated.
Abstract: Measurement of two-dimensional bending in a structural element using intrinsic optical fibre strain gauges would normally require three sensors to be attached to, or embedded within, the structure. The same measurement can now be made using a single multi-core optical fibre, reducing deployment cost and increasing practicality. Fabrication of a novel three-core photonic crystal fibre is described. The ability of the fibre sensor to measure bend in two dimensions is demonstrated in the laboratory using interferometric interrogation at a single wavelength. Deployment of the sensor to measure the deformation of a bridge undergoing loading trials is described.
94 citations
TL;DR: The excitation by flexural acoustic waves of an individual cladding mode in a single-mode photonic crystal fiber gives the basis for developing a family of acousto-optic devices based on photonic crystals fibers.
Abstract: We report the excitation by flexural acoustic waves of an individual cladding mode in a single-mode photonic crystal fiber. The propagation constant and the field distributions of the mode have been investigated by use of this technique. The results give the basis for developing a family of acousto-optic devices based on photonic crystal fibers.
75 citations
TL;DR: The theory of optical superlattices in fiber Bragg gratings is developed in detail, treating both the acousto-optic and the fixed-grating cases.
Abstract: The superposition of a long-period grating and a fiber Bragg grating, which we call an optical superlattice, causes high-efficiency narrow-band reflections to be induced on either side of the Bragg wavelength. This effect was recently observed experimentally in a fiber-based acousto-optic superlattice modulator. We develop in detail the theory of optical superlattices in fiber Bragg gratings, treating both the acousto-optic and the fixed-grating cases. Applications include reconfigurable wavelength division multiplexers, fiber lasers and sensors, tunable filters, modulators, and frequency shifters.
52 citations
TL;DR: In this paper, the effect of the strain on a tapered fiber acoustooptic filter was studied and the center wavelengths of the resonances were dramatically affected by strain.
Abstract: A study into the effect of the strain on a tapered fibre acoustooptic filter is presented. The centre wavelengths of the resonances are dramatically affected by strain: >500 nm tunability range has been obtained for a maximum applied strain of 1.3/spl times/10/sup -2/.
38 citations
TL;DR: In this paper, a near-field optical microscope was incorporated into one arm of a Mach-Zehnder interferometer to measure the intensity and phase in the near field of both propagating and evanescent fields.
Abstract: To fully characterize photonic crystal guided wave optical devices, one needs to measure the spatial variation of both the phase and amplitude of the electromagnetic field. In this work, we simultaneously measure the intensity and phase in the near field of both propagating and evanescent fields by incorporating a scanning near-field optical microscope into one arm of a Mach–Zehnder interferometer. We demonstrate the technique by imaging the phase fronts of an evanescent wave formed by total internal reflection and by measuring the phase variation in the LP11 mode in an overmoded optical fiber.
TL;DR: In this paper, a one-dimensional grating microstructure was fabricated on a tapered optical fiber and its acoustic properties were experimentally studied using a focused CO2 laser, which showed a strong frequency stop-band for flexural waves.
Abstract: A one-dimensional grating microstructure was fabricated on a tapered optical fiber and its acoustic properties experimentally studied The structure consisted of a number of concatenated and equally spaced microtapers, fabricated using a focused CO2 laser Acoustic characterization of the device showed a strong frequency stop-band for flexural waves Such structures are suitable as frequency-selective acoustic mirrors in acousto-optic fiber devices
07 Mar 2000
TL;DR: A 2.9 nm bandwidth AOTF was fabricated from highly uniform, tapered optical fiber in this paper, which had an excess loss of 0.02 dB, >20 dB extinction, was polarization insensitive, and had the smallest bandwidth-length product reported to date.
Abstract: A 2.9 nm bandwidth AOTF was fabricated from highly uniform, tapered optical fiber. The filter had an excess loss of 0.02 dB, >20 dB extinction, was polarization insensitive, and had the smallest bandwidth-length product reported to date.
07 Mar 2000
TL;DR: The Holey photonic crystal fiber (PCF) as discussed by the authors consists of a thread of glass with microscopic air capillaries running along its length, and its many remarkable properties are overturning the basic precepts of textbook fiber technology.
Abstract: "holey" photonic crystal fibre (PCF) consists of a thread of glass with microscopic air capillaries running along its length. Its many remarkable properties are overturning the basic precepts of textbook fiber technology.
07 May 2000
TL;DR: In this paper, the authors have observed ultra-broad supercontinuum generation in a conventional telecommunications optical fiber (cutoff wavelength ~1250 nm, NA = 0.1).
Abstract: Summary form only given. We have observed ultra-broad supercontinuum generation in a conventional telecommunications optical fibre (cutoff wavelength ~1250 nm, NA = 0.1). The fibre was tapered (heated and stretched in a flame) to reduce its diameter to 1.8 μm uniformly over a 90 mm length, without significant loss. Pulses (200-500 fs) from a Ti:sapphire laser tuned to 850 nm were launched into the fibre. The output spectrum for a pulse energy of 3.2nJ, corresponding to 240 mW average power, is plotted. Our tapered fibres (mounted in simple dustproof housings) were robust, surviving several days without degradation. We therefore anticipate that tapered fibres will be effective hosts for a number of other nonlinear effects also.
TL;DR: In this article, a microcavity composed of porous silicon multilayer mirrors was electrochemically etched and doped with erbium, and the reflectivity and photoluminescence spectra were presented.
Abstract: A microcavity composed of porous silicon multilayer mirrors was electrochemically etched and doped with erbium. Measurements of the reflectivity and photoluminescence spectra are presented. Thermal processing under a nitrogen atmosphere optically activated the erbium ions. Photopumping yielded room temperature emission around 1.54 μm from the erbium-doped samples with the emitted light strongly modified by the microcavity structure. Emission spectra with a peak at 1.536 μm had a full width at half maximum of ∼6 nm.
TL;DR: In this article, the emission and reflection properties of different porous silicon single and multilayer structures have been investigated in order to understand further and exploit the nature of light propagation within them.
Abstract: Porous silicon photoluminescence and electroluminescence can be controlled by periodically modulating the material porosity to form high quality multilayer stacks and microcavities. Important issues not yet fully addressed are (a) the precise role played by this microstructuring, given that the luminescence is distributed throughout the entire structure and that the low porosity layers are highly absorbing at short wavelengths, and (b) whether the quality of such microcavities could be sufficient to support lasing. Using both experimental and theoretical techniques, the emission and reflection properties of different porous silicon single and multilayer structures have been investigated in order to understand further and exploit the nature of light propagation within them.
TL;DR: In this article, the effect of thermal processing on multilayer porous silicon microcavities was investigated, where the reflectivity spectra were measured before and after thermal processing and it was found that thermal processing not only changed the effective refractive indices of individual porous layers but also roughened their respective interfaces.
Abstract: The effect of thermal processing, that gave limited oxidation from annealing under N2 atmosphere, on multilayer porous silicon (P-Si) microcavities has been investigated. The reflectivity spectra were measured before and after thermal processing. The observation of multilayer samples by scanning electron microscopy has shown unexpected expansion and compression of P-Si layers. It is found that thermal processing not only changed the effective refractive indices of the individual porous layers but also roughened their respective interfaces.
07 Mar 2000
TL;DR: In this paper, singlemode fiber couplers are formed by fusing together two tapered fibres using a carbon dioxide laser, which will allow a miniature version of many all-fibre devices to be made.
Abstract: Single-mode fibre couplers considerably less than 1 mm long are formed by fusing together two tapered fibres using a carbon dioxide laser. This will allow a miniature version of many all-fibre devices to be made.
10 Sep 2000
TL;DR: In this article, a tapered optical fiber of 1 micron diameter and 30 mm length was used to generate a 200 nm wide supercontinuum from the 0.26 nJ femtosecond pulses emitted by a Ti:sapphire laser.
Abstract: Summary form only given. A tapered optical fibre of 1 micron diameter and 30 mm length was used to generate a 200 nm wide supercontinuum from the 0.26 nJ femtosecond pulses emitted by a Ti:sapphire laser.
14 May 2000
TL;DR: In this paper, the modes of a femtosecond mode-locked laser are distributed uniformly in frequency space and can be used like a ruler to measure large optical frequency differences.
Abstract: We have shown that the modes of a femtosecond mode-locked laser are distributed uniformly in frequency space and can be used like a ruler to measure large optical frequency differences. To measure absolute optical frequencies we use nonlinear optics for the conversion into a large frequency interval. Unlike the complex harmonic frequency chains used in the past this new approach uses only a few laser sources (ideally just one) and is nevertheless capable of measuring almost any optical frequency with the same set up. We applied the new technique to determine the absolute frequencies of the cesium D/sub 1/ line at 335 THz, of several components in I/sub 2/ around 563 THz, the sharp /sup 115/In/sup +/5s/sup 21/S/sub 0/-5s5p/sup 3/P/sub 0/ transition at 1267 THz and the hydrogen 1S-2S transition at 2466 THz.
01 Jan 2000
TL;DR: In this article, the authors describe how new optical properties arise in such media, and how they can be used to form novel optical waveguide structures, and describe how these properties arise due to the interference of the light scattered at different interfaces.
Abstract: Photonic crystals are formed of a regularly patterned microstructured material, with a pitch comparable to the optical wavelength. These materials exhibit unusual optical properties due to the interference of the light scattered at the different interfaces, and this has remarkable consequences such as the formation of photonic band gaps. One way of making 2-dimensional photonic crystal materials is to use the technology of optical fibre fabrication. We describe how new optical properties arise in such media, and how they can be used to form novel optical waveguide structures.
10 Sep 2000
TL;DR: In this paper, the authors discuss the parameters affecting the generation of a supercontinuum, its properties and possible application of this new source to areas such as spectrometry, absolute frequency metrology and white light interferometry.
Abstract: Summary form only given. Photonic crystal fibre (PCF) has recently been demonstrated to be an excellent source of extremely broadband supercontinuum radiation. This is due to the small core sizes and to the novel group velocity dispersion (GVD) imparted to the guided mode by the array of air holes which form the fibre cladding. With large air holes in the cladding and a small core, the wavelength for zero GVD may be reduced from beyond 1.3 /spl mu/m for conventional fibres to the region of 500-900 nm. We shall discuss the parameters affecting the generation of a supercontinuum, its properties and possible application of this new source to areas such as spectrometry, absolute frequency metrology and white light interferometry.
07 May 2000
TL;DR: In this paper, it was shown that if the core and cladding glasses are identical, the strong wavelength dependence of the cladding effective index gives V an upper bound and allows the fibre to be endlessly single mode.
Abstract: Summary form only given. Conventionally, optical fibres become stronger waveguides as wavelength decreases. The fundamental mode becomes more confined to the core, successive higher-order modes appear, and the V-value rises without limit. Photonic crystal fibres (PCFs) have holes in the cladding that run along the length of the fibre. These give the cladding a lower effective refractive index than the glass it is made from, allowing: a solid core (a missing hole) to guide by total internal reflection. If the core and cladding glasses are identical, the strong wavelength dependence of the cladding effective index gives V an upper bound and allows the fibre to be endlessly single mode.
Proceedings Article•
12 May 2000TL;DR: In this article, a photonic crystal film of infinite thickness is considered, where the photonic lattice is a triangular lattice of cylindrical holes etched into a medium having a higher refractive index than the semi-infinite regions.
Abstract: Summary form only given. We present some results of rigorous calculations for a photonic crystal film positioned between two semi-infinite regions of uniform refractive index, where the photonic crystal film itself is a triangular lattice of cylindrical holes etched into a medium having a higher refractive index than the semi-infinite regions. We start by considering a photonic crystal film of infinite thickness. Let the z axis be perpendicular to the surface of the film, and let the 'in-plane' coordinates (parallel to the surface of the film) be (x,y).
Proceedings Article•
12 May 2000TL;DR: In this paper, a photonic crystal fiber (PCF) with a more-or-less regular array of microscopic air holes running along its length is considered, where light is guided at a missing (filled in) air hole in an array of holes.
Abstract: Summary form only given. A photonic crystal fibre (PCF) is an optical fibre with a more-or-less regular array of microscopic air holes running along its length. Proposed in 1992, the first working example was made in 1996. In the paper we consider a PCF in which light is guided at a missing (filled in) air hole in an array of holes. This high index defect guides by modified total internal reflection. The unusual dispersion properties of the cladding with its array of air holes impart novel dispersion to the guided mode. In particular it is possible to obtain zero group velocity dispersion in the visible/near IR in a single mode PCF, with anomalous GVD at longer wavelengths. This is unattainable in conventional fibres where the zero GVD point must be beyond 1.27 /spl mu/m. Such modified dispersion in PCF brings the exciting possibility of generating solitons at wavelengths within the tuning range of Ti:sapphire in the very near infrared. A similar fibre has also been shown experimentally to generate white-light supercontinua over the visible and infrared.
12 Jul 2000
TL;DR: In this article, the band gap and effective index waveguiding properties of photonic crystal fiber have been described, and the remarkable new properties they possess have been demonstrated in terms of band gap, effective index, and effective-index waveguide.
Abstract: Photonic crystal fiber is a pure silica fiber with a regular array of air holes running down its length. We describe band-gap and effective-index waveguiding in these structures, and the remarkable new properties they possess.
Proceedings Article•
12 May 2000TL;DR: In this article, the authors proposed a method to demonstrate very low out-of-plane leakage while preserving the advantages offered by photonic crystals, where simple multilayer stacks can behave like quasi-metals for incidence from low refractive index media.
Abstract: Summary form only given. Near stop-band edges, periodically microstructured media (photonic crystals) exhibit strong temporal and spatial dispersion. The challenge is to demonstrate very low out-of-plane leakage while preserving the advantages offered by photonic crystals. Among the devices being actively worked on are waveguides which are modeless within a range of frequencies, vertical emitting microcavities with very high quality factors, new kinds of efficient microlaser, and wavelength-sensitive filters for telecommunications. Simple multilayer stacks can behave like quasi-metals for incidence from low refractive index media.