Generation of a phase-locked Raman frequency comb in gas-filled
hollow-core photonic crystal fiber
A. Abdolvand,
A. M. Walser,
M. Ziemienczuk,
T. Nguyen,
P. St J. Russell
OPTICS LETTERS
37
(21)
4362-4364
(2012)
In a relatively simple setup consisting of a microchip laser as pump source and two hydrogen-filled hollow-core photonic crystal fibers, a broad, phase-locked, purely rotational frequency comb is generated. This is achieved by producing a clean first Stokes seed pulse in a narrowband guiding photonic bandgap fiber via stimulated Raman scattering and then driving the same Raman transition resonantly with a pump and Stokes fields in a second broad-band guiding kagome-style fiber. Using a spectral interferometric technique based on sum frequency generation, we show that the comb components are phase locked. (C) 2012 Optical Society of America
Influence of timing jitter on nonlinear dynamics of a photonic crystal
fiber ring cavity
M. Schmidberger,
W. Chang,
P. St. J. Russell,
N. Y. Joly
OPTICS LETTERS
37
(17)
3576-3578
(2012)
We demonstrate that timing jitter has a strong influence on supercontinua generated in a photonic crystal fiber ring cavity synchronously pumped by 140 fs pulses. The global dynamics with respect to cavity detuning is analyzed both numerically and experimentally by tracking the cavity pulse energy. The results show that low-frequency timing jitter, induced by both the pump oscillator and the external cavity, masks the fine underlying bifurcation structure of the system. Numerical simulations in the absence of timing jitter reveal that the system dynamics fall into four qualitatively different regimes. The existence of these regimes is experimentally observed in first-return diagrams. (c) 2012 Optical Society of America
Excitation of Orbital Angular Momentum Resonances in Helically Twisted
Photonic Crystal Fiber
G. K. L. Wong,
M. S. Kang,
H. W. Lee,
F. Biancalana,
C. Conti,
T. Weiss,
P. St J. Russell
Spiral twisting offers additional opportunities for controlling the loss, dispersion, and polarization state of light in optical fibers with noncircular guiding cores. Here, we report an effect that appears in continuously twisted photonic crystal fiber. Guided by the helical lattice of hollow channels, cladding light is forced to follow a spiral path. This diverts a fraction of the axial momentum flow into the azimuthal direction, leading to the formation of discrete orbital angular momentum states at wavelengths that scale linearly with the twist rate. Core-guided light phase-matches topologically to these leaky states, causing a series of dips in the transmitted spectrum. Twisted photonic crystal fiber has potential applications in, for example, band-rejection filters and dispersion control.
Fission of solitons in continuous-wave supercontinuum
E. J. R. Kelleher,
M. Erkintalo,
J. C. Travers
OPTICS LETTERS
37
(24)
5217-5219
(2012)
We use numerical simulations to revisit the generation of fiber supercontinua pumped by partially coherent continuous-wave (CW) sources. Specifically, we show that intensity fluctuations characteristic of temporal partial coherence can be described as a stochastic train of high-order solitons, whose individual dynamics drive continuum formation. For sources with sufficiently low coherence, these solitons actually undergo fission rather than modulation instability, changing the nature of the CW supercontinuum evolution. (C) 2012 Optical Society of America
Excitation of a nanowire "molecule" in gold-filled photonic crystal
fiber
H. W. Lee,
M. A. Schmidt,
P. St. J. Russell
OPTICS LETTERS
37
(14)
2946-2948
(2012)
A pair of gold nanowires, incorporated into a photonic crystal fiber, acts as a plasmonic "molecule." Hybridized modes are excited at specific wavelengths by launching light into the glass core. The formation of bonding and antibonding solutions results in a modal splitting of more than 100 nm, even though the spatial separation between the wires is larger than 3 mu m. The study provides insight into multiwire plasmonic devices with applications as polarizers or filters in near-field optics, nonlinear plasmonics, optical sensing, and telecommunications. (C) 2012 Optical Society of America
Polarisation-resolved near-field mapping of a coupled gold nanowire
array
Patrick Uebel,
Markus A. Schmidt,
Howard W. Lee,
Philip St. J. Russell
We report direct observation of the 2D transverse near-field intensity and polarisation distribution of surface plasmon polaritons guided on metal nanowires. Quadrupolar modes are excited on an array of coupled nanowires arranged around the central glass core in a photonic crystal fibre, with lobes whose orientation depends on the polarisation state of the launched core light. The radial electric field is resolved using a polarization sensitive near-field probe in light-collection mode. (C) 2012 Optical Society of America
Stabilised Biosensing Using Needle-Based Recess Electrodes
Salzitsa Anastasova,
Anna-Maria Spehar-Deleze,
Dale Bickham,
Patrick Uebel,
Markus Schmidt,
Philip Russell,
Pankaj Vadgama
A recess disk electrode for amperometric monitoring of oxygen and glucose is reported. The basic design of sensor is a needle structure for easy implantation, embodying a gold filled silica capillary with a 80 mu m inner diameter working electrode. Recess and inlaid disc electrodes, placed inside stainless steel tubes which served as a counter/reference electrode, were compared. The working electrode surface was modified with different treatments and barrier membranes to achieve selectivity for the analytes of interest. The basic needle format is ideal for in vivo use, and the format is easily extendable to other analyte targets. The sensors show linear working range for oxygen up to 160 mmHg partial pressure of oxygen, and for glucose from 1 to 10 mM. Bio-fouling, as assessed by exposure to bovine serum albumin, was significantly reduced. Response times for the recess construct was increased but remained within the acceptable range for physiological monitoring. The operational stability of the sensors is demonstrated as well as the interference-free detection of peroxide in the presence of physiologically relevant levels of ascorbic acid, uric acid, acetaminophen, and catechol. Preliminary in vivo tests showed excellent response towards glucose.
Kagome hollow-core photonic crystal fiber probe for Raman spectroscopy
Petru Ghenuche,
Silke Rammler,
Nicolas Y. Joly,
Michael Scharrer,
Michael Frosz,
Jerome Wenger,
Philip St J. Russell,
Herve Rigneault
OPTICS LETTERS
37
(21)
4371-4373
(2012)
We demonstrate the use of a large-pitch Kagome-lattice hollow-core photonic crystal fiber probe for Raman spectroscopy. The large transmission bandwidth of the fiber enables both the excitation and Raman beams to be transmitted through the same fiber. As the excitation beam is mainly transmitted through air inside the hollow core, the silica luminescence background is reduced by over 2 orders of magnitude as compared to standard silica fiber probes, removing the need for fiber background subtraction. (C) 2012 Optical Society of America
Plasma-Induced Asymmetric Self-Phase Modulation and Modulational
Instability in Gas-Filled Hollow-Core Photonic Crystal Fibers
Mohammed F. Saleh,
Wonkeun Chang,
John C. Travers,
Philip St J. Russell,
Fabio Biancalana
We study theoretically the propagation of relatively long pulses with ionizing intensities in a hollow-core photonic crystal fiber filled with a Raman-inactive noble gas. Because of photoionization, an extremely asymmetric self-phase modulation and a new kind of "universal" plasma-induced modulational instability appear in both normal and anomalous dispersion regions. We also show that it is possible to spontaneously generate a plasma-induced continuum of blueshifting solitons, opening up new possibilities for pushing supercontinuum generation towards shorter and shorter wavelengths.
Reconfigurable Optothermal Microparticle Trap in Air-Filled Hollow-Core
Photonic Crystal Fiber
O. A. Schmidt,
M. K. Garbos,
T. G. Euser,
P. St. J. Russell
We report a novel optothermal trapping mechanism that occurs in air-filled hollow-core photonic crystal fiber. In the confined environment of the core, the motion of a laser-guided particle is strongly influenced by the thermal-gradient- driven flow of air along the core surface. Known as "thermal creep flow,'' this can be induced either statically by local heating, or dynamically by the absorption (at a black mark placed on the fiber surface) of light scattered by the moving particle. The optothermal force on the particle, which can be accurately measured in hollow-core fiber by balancing it against the radiation forces, turns out to exceed the conventional thermophoretic force by 2 orders of magnitude. The system makes it possible to measure pN-scale forces accurately and to explore thermally driven flow in micron-scale structures.
Nonlinear fiber-optic strain sensor based on four-wave mixing in microstructured optical fiber
Bobo Gu,
Wu Yuan,
Michael H. Frosz,
A. Ping Zhang,
Sailing He,
Ole Bang
OPTICS LETTERS
37
(5)
794-796
(2012)
We demonstrate a nonlinear fiber-optic strain sensor, which uses the shifts of four-wave mixing Stokes and anti-Stokes peaks caused by the strain-induced changes in the structure and refractive index of a microstructured optical fiber. The sensor thus uses the inherent nonlinearity of the fiber and does not require any advanced post-processing of the fiber. Strain sensitivity of -0.23 pm/mu epsilon is achieved experimentally and numerical simulations reveal that for the present fiber the sensitivity can be increased to -4.46 pm/mu epsilon by optimizing the pump wavelength and power. (C) 2012 Optical Society of America
Optomechanical Nonlinearity in Dual-Nanoweb Structure Suspended Inside
Capillary Fiber
A. Butsch,
M. S. Kang,
T. G. Euser,
J. R. Koehler,
S. Rammler,
R. Keding,
P. St J. Russell
A novel kind of nanostructured optical fiber, displaying an extremely high and optically broadband optomechanical nonlinearity, is presented. It comprises two closely spaced ultrathin glass membranes (webs) suspended in air and attached to the inner walls of a glass fiber capillary. Light guided in this dual-web structure can exert attractive or repulsive pressure on the webs, causing them to be pushed together or pulled apart. The elastic deflection of the webs is, in turn, coupled to the electromagnetic field distribution and results in a change in the effective refractive index within the fiber. Employing a pump-probe technique in an interferometric setup, optomechanically induced refractive index changes more than 10(4) times larger than the Kerr effect are detected. Theoretical estimates of the optomechanical nonlinearity agree well with the experimental results. The dual-web fiber combines the sensitivity of a microoptomechanical device with the versatility of an optical fiber and could trigger new developments in the fields of nonlinear optics, optical metrology, and sensing.
Rare-earth ion doped TeO2 and GeO2 glasses as laser materials
PROGRESS IN MATERIALS SCIENCE
57
(8)
1426-1491
(2012)
| Journal
Germanium oxide (GeO2) and tellurium oxide (TeO2) based glasses are classed as the heavy metal oxide glasses, with phonon energies ranging between 740 cm(-1) and 880 cm(-1). These two types of glasses exhibit unique combinations of optical and spectroscopic properties, together with their attractive environmental resistance and mechanical properties. Engineering such a combination of structural, optical and spectroscopic properties is only feasible as a result of structural variability in these two types of glasses, since more than one structural units (TeO4 bi-pyramid, TeO3 trigonal pyramid, and TeO3+delta polyhedra) in tellurite and (GeO4 tetrahedron, GeO3 octahedron) in GeO2 based glasses may exist, depending on composition. The presence of multiple structural moities creates a range of dipole environments which is ideal for engineering broad spectral bandwidth rare-earth ion doped photonic device materials, suitable for laser and amplifier devices. Tellurite glasses were discovered in 1952, but remained virtually unknown to materials and device engineers until 1994 when unusual spectroscopic, nonlinear and dispersion properties of alkali and alkaline earth modified tellurite glasses and fibres were reported. Detailed spectroscopic analysis of Pr3+, Nd3+, Er3+ and Tm3+ doped tellurite glasses revealed its potential for laser and amplifier devices for optical communication wavelengths. This review summarises the thermal and viscosity properties of tellurite and germanate glasses for fibre fabrication and compares the linear loss for near and mid-IR device engineering. The aspects of glass preform fabrication for fibre engineering is discussed by emphasising the raw materials processing with casting of preforms and fibre fabrication. The spectroscopic properties of tellurite and germanate glasses have been analysed with special emphasis on oscillator strength and radiative rate characteristics for visible, near IR and mid-IR emission. The review also compares the latest results in the engineering of lasers and amplifiers, based on fibres for optical communication and mid-IR. The achievements in the areas of near-IR waveguide and mid-IR bulk glass, fibre, and waveguide lasers are discussed. The latest landmark results in mode-locked 2 mu m bulk glass lasers sets the precedence for engineering nonlinear and other laser devices for accessing the inaccessible parts of the mid-IR spectrum and discovering new applications for the future. (c) 2012 Elsevier Ltd. All rights reserved.
Extreme supercontinuum generation to the deep UV
S. P. Stark,
J. C. Travers,
P. St. J. Russell
OPTICS LETTERS
37
(5)
770-772
(2012)
We report the formation of an ultrabroad supercontinuum down to 280 nm in the deep UV by pumping sharply tapered (5-30 mm taper lengths) solid-core photonic crystal fibers with 130 fs, 2 nJ pulses at 800 nm. The taper moves the point of soliton fission to a position where the core is narrower, a process that requires normal dispersion at the input face of the fiber. We find that the generation of deep-UV radiation is limited by strong two-photon absorption in the silica. (C) 2012 Optical Society of America
Dynamics of optomechanical spatial solitons in dual-nanoweb structures
C. Conti,
A. Butsch,
F. Biancalana,
P. St J. Russell
We theoretically investigate the stability and dynamics of self-channeled beams that form via nonlocal optomechanical interactions in dual-nanoweb microstructured fibers. These beams represent a class of spatial soliton.
Optomechanical Self-Channeling of Light in a Suspended Planar
Dual-Nanoweb Waveguide
A. Butsch,
C. Conti,
F. Biancalana,
P. St J. Russell
It is shown that optomechanical forces can cause nonlinear self-channeling of light in a planar dual-slab waveguide. A system of two parallel silica nanowebs, spaced similar to 100 nm and supported inside a fiber capillary, is studied theoretically and an iterative scheme developed to analyze its nonlinear optomechanical properties. Steady-state field distributions and mechanical deformation profiles are obtained, demonstrating that self-channeling is possible in realistic structures at launched powers as low as a few mW. The differential optical nonlinearity of the self-channeled mode can be as much as 10 x 10(6) times higher than the corresponding electronic Kerr nonlinearity. It is also intrinsically broadband, does not utilize resonant effects, can be viewed as a consequence of the extreme nonlocality of the mechanical response, and in fact is a notable example of a so-called accessible soliton.
Photonic crystal fibre as an optofluidic reactor for the measurement of
photochemical kinetics with sub-picomole sensitivity
Gareth O. S. Williams,
Jocelyn S. Y. Chen,
Tijmen G. Euser,
Philip St J. Russell,
Anita C. Jones
Photonic crystal fibre constitutes an optofluidic system in which light can be efficiently coupled into a solution-phase sample, contained within the hollow core of the fibre, over long path-lengths. This provides an ideal arrangement for the highly sensitive monitoring of photochemical reactions by absorption spectroscopy. We report here the use of UV/vis spectroscopy to measure the kinetics of the photochemical and thermal cis-trans isomerisation of sub-picomole samples of two azo dyes within the 19-mu m diameter core of a photonic crystal fibre, over a path length of 30 cm. Photoisomerisation quantum yields are the first reported for "push-pull'' azobenzenes in solution at room temperature; such measurements are challenging because of the fast thermal isomerisation process. Rate constants obtained for thermal isomerisation are in excellent agreement with those established previously in conventional cuvette-based measurements. The high sensitivity afforded by this intra-fibre method enables measurements in solvents in which the dyes are too insoluble to permit conventional cuvette-based measurements. The results presented demonstrate the potential of photonic crystal fibres as optofluidic elements in lab-on-a-chip devices for photochemical applications.
Ultra-narrow linewidth CW sub-THz generation using GS based OFCG and
n-i-pn-i-p superlattice photomixers
A. R. Criado,
C. de Dios,
G. H. Doehler,
S. Preu,
S. Malzer,
S. Bauerschmidt,
H. Lu,
A. C. Gossard,
P. Acedo
A report is presented on the photonic synthesis of ultra-narrow line-width continuous-wave (CW) sub-THz signals using a gain-switching (GS) based optical frequency comb generator (OFCG), selective optical filtering and a n-i-pn-i-p superlattice photomixer. This setup provides continuous tunability with a tuning resolution in the range of 0.1 Hz at 120 GHz and full width at half maximum of the generated signals below the limits of the measurement setup (< 10 Hz). The advantages of this system make it a very good candidate for applications requiring extremely low phase noise and continuous tunability, such as high resolution spectroscopy in the sub-THz and THz range.
Metrology of laser-guided particles in air-filled hollow-core photonic
crystal fiber
O. A. Schmidt,
M. K. Garbos,
T. G. Euser,
P. St. J. Russell
OPTICS LETTERS
37
(1)
91-93
(2012)
Micrometer-sized particles are trapped in front of an air-filled hollow-core photonic crystal fiber using a novel dual-beam trap. A backward guided mode produces a divergent beam that diffracts out of the core, and simultaneously a focused laser beam launches a forward-propagating mode into the core. By changing the backward/forward power balance, a trapped particle can be selectively launched into the hollow core. Once inside, particles can be optically propelled along several meters of fiber with mobilities as high as 19 cm. s(-1) W-1 (precisely measured using in-fiber Doppler velocimetry). The results are in excellent agreement with theory. The system allows determination of fiber loss as well as the mass density and refractive index of single particles. c 2011 Optical Society of America
Numerical Solution and Experimental Validation of the Drawing Process of
Six-Hole Optical Fibers Including the Effects of Inner Pressure and
Surface Tension
Giovanni Luzi,
Philipp Epple,
Michael Scharrer,
Ken Fujimoto,
Cornelia Rauh,
Antonio Delgado
JOURNAL OF LIGHTWAVE TECHNOLOGY
30
(9)
1306-1311
(2012)
| Journal
Microstructured optical fibers (MOFs) achieve their desired performance via a pattern of holes that run trough the whole length of the fiber. The variation of the hole pattern allows the production of a variety of optical effects. However, the cross-sectional hole structure can be different from that designed in the preform, due to the combined effects of surface tension and internal pressure. The present paper focuses on the comparison between experiments and numerical calculation of a six hole-optical fiber taking into account the effects of surface tension and internal hole-pressure, since those are of essential importance during drawing. It is shown that the numerical computations deliver reliable results for practical applications and can be used as a predictive tool for fiber development, as long as the inner pressure or the temperature do not exceed too high values.
Microfluidic integration of photonic crystal fibers for online
photochemical reaction analysis
S. Unterkofler,
R. J. McQuitty,
T. G. Euser,
N. J. Farrer,
P. J. Sadler,
P. St. J. Russell
OPTICS LETTERS
37
(11)
1952-1954
(2012)
Liquid-filled hollow-core photonic crystal fibers (HC-PCFs) are perfect optofluidic channels, uniquely providing low-loss optical guidance in a liquid medium. As a result, the overlap of the dissolved specimen and the intense light field in the micronsized core is increased manyfold compared to conventional bioanalytical techniques, facilitating highly-efficient photoactivation processes. Here we introduce a novel integrated analytical technology for photochemistry by microfluidic coupling of a HC-PCF nanoflow reactor to supplementary detection devices. Applying a continuous flow through the fiber, we deliver photochemical reaction products to a mass spectrometer in an online and hence rapid fashion, which is highly advantageous over conventional cuvette-based approaches. (C) 2012 Optical Society of America
Intermodal stimulated Raman scattering in hydrogen-filled hollow-core
photonic crystal fiber
M. Ziemienczuk,
A. M. Walser,
A. Abdolvand,
P. St. J. Russell
JOURNAL OF THE OPTICAL SOCIETY OF AMERICA B-OPTICAL PHYSICS
29
(7)
1563-1568
(2012)
Stimulated Raman scattering is investigated in a slightly multimode gas-filled hollow-core photonic crystal fiber. Although, second-order Stokes light appears in the fundamental mode below a certain threshold energy, it is observed to switch to a two-lobed higher order mode above this threshold. Conversion to the higher order mode is made possible by the creation of a two-lobed moving coherence wave in the gas that provides both phase-matching and a strong intermodal pump-Stokes overlap. A theoretical model is developed, based on this physical interpretation that agrees quantitatively with the experimental results. The results suggest new opportunities for all-fiber gas-based nonlinear processes requiring phase-matching, such as coherent anti-Stokes Raman scattering, as well as providing a means (for example) of efficiently converting light from a higher order pump mode to a fundamental Stokes mode. (C) 2012 Optical Society of America
Ultra-Low Concentration Monitoring of Catalytic Reactions in Photonic
Crystal Fiber
Ana M. Cubillas,
Matthias Schmidt,
Michael Scharrer,
Tijmen G. Euser,
Bastian J. M. Etzold,
Nicola Taccardi,
Peter Wasserscheid,
Philip St. J. Russell
CHEMISTRY-A EUROPEAN JOURNAL
18
(6)
1586-1590
(2012)
| Journal
Kontakt
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