Showing papers by "Philip St. J. Russell published in 2013"
TL;DR: It is shown that bright, high quality, localized bands of UV light can be generated at all wavelengths across this range, and the coherence of the deep-UV dispersive wave radiation numerically investigated.
Abstract: An efficient and tunable 176-550 nm source based on the emission of resonant dispersive radiation from ultrafast solitons at 800 nm is demonstrated in a gas-filled hollow-core photonic crystal fiber (PCF). By careful optimization and appropriate choice of gas, informed by detailed numerical simulations, we show that bright, high quality, localized bands of UV light (relative widths of a few percent) can be generated at all wavelengths across this range. Pulse energies of more than 75 nJ in the deep-UV, with relative bandwidths of ~3%, are generated from pump pulses of a few μJ. Excellent agreement is obtained between numerical and experimental results. The effects of positive and negative axial pressure gradients are also experimentally studied, and the coherence of the deep-UV dispersive wave radiation numerically investigated.
147 citations
TL;DR: Analysis shows that the tension-induced shift in resonance wavelength is determined both by the photoelastic effect and by the change in twist rate, while the torsion-induced wavelength shift depends only on the change on twist rate.
Abstract: Solid-core photonic crystal fiber (PCF) with a permanent helical twist exhibits dips in its transmission spectrum at certain wavelengths. These are associated with the formation of orbital angular momentum states in the cladding. Here we investigate the tuning of these states with mechanical torque and axial tension. The dip wavelengths are found to scale linearly with both axial strain and mechanical twist rate. Analysis shows that the tension-induced shift in resonance wavelength is determined both by the photoelastic effect and by the change in twist rate, while the torsion-induced wavelength shift depends only on the change in twist rate. Twisted PCF can act as an effective optically monitored torque-tension transducer, twist sensor, or strain gauge.
79 citations
TL;DR: The use of photonic crystal fibers in chemistry and sensing is reviewed and recent applications as catalytic microreactors are presented in this article, where results on homogeneous catalysis and the immobilization of homogeneous and heterogeneous catalysts in the fiber channels are discussed.
Abstract: The concept of employing photonic crystal fibers for chemical and (photo)-catalytical transformations is presented. These optofluidic microdevices represent a versatile platform where light and fluids can interact for spectroscopic or photoactivation purposes. The use of photonic crystal fibers in chemistry and sensing is reviewed and recent applications as catalytic microreactors are presented. Results on homogeneous catalysis and the immobilization of homogeneous and heterogeneous catalysts in the fiber channels are discussed. The examples demonstrate that combining catalysis and the excellent light guidance of photonic crystal fibers provides unique features for example, for photocatalytic activation and quantitative photospectroscopic reaction analysis.
31 citations
TL;DR: This mode-based optical conveyor belt combines long-range transport of microparticles with a positional accuracy of 1 µm and has potential uses in waveguide-based optofluidic systems.
Abstract: We show how microparticles can be moved over long distances and precisely positioned in a low-loss air-filled hollow-core photonic crystal fiber using a coherent superposition of two co-propagating spatial modes, balanced by a backward-propagating fundamental mode. This creates a series of trapping positions spaced by half the beat-length between the forward-propagating modes (typically a fraction of a millimeter). The system allows a trapped microparticle to be moved along the fiber by continuously tuning the relative phase between the two forward-propagating modes. This mode-based optical conveyor belt combines long-range transport of microparticles with a positional accuracy of 1 µm. The technique also has potential uses in waveguide-based optofluidic systems.
30 citations
TL;DR: This work introduces a unique method for laser‐propelling individual cells over distances of 10s of cm through stationary liquid in a microfluidic channel using liquid‐filled hollow‐core photonic crystal fiber (HC‐PCF).
Abstract: We introduce a unique method for laser-propelling individual cells over distances of 10s of cm through stationary liquid in a microfluidic channel. This is achieved by using liquid-filled hollow-core photonic crystal fiber (HC-PCF). HC-PCF provides low-loss light guidance in a well-defined single mode, resulting in highly uniform optical trapping and propulsive forces in the core which at the same time acts as a microfluidic channel. Cells are trapped laterally at the center of the core, typically several microns away from the glass interface, which eliminates adherence effects and external perturbations. During propagation, the velocity of the cells is conveniently monitored using a non-imaging Doppler velocimetry technique. Dynamic changes in velocity at constant optical powers up to 350 mW indicate stress-induced changes in the shape of the cells, which is confirmed by bright-field microscopy. Our results suggest that HC-PCF will be useful as a new tool for the study of single-cell biomechanics. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
22 citations
TL;DR: The use of photonic crystal fibres (PCF) as spectrofluorimetric systems in which sample solutions are excited within the microstructure of the fibre are reported and the measurement of fluorescence spectra and fluorescence lifetimes in each excitation regimes are demonstrated.
Abstract: We report the use of photonic crystal fibres (PCF) as spectrofluorimetric systems in which sample solutions are excited within the microstructure of the fibre. The use of intra-fibre excitation has several advantages that combine to enable highly sensitive measurements of fluorescence spectra and lifetimes: long path-lengths are achieved by the efficient guidance of the fundamental mode; sample volumes contained within the micron-scale structure are very small, only a few nanolitres per cm of path; collection and guidance of the emitted fluorescence is efficient and the fluorescence lifetime is unperturbed. Fluorophores in bulk solution can be studied in hollow core PCF, whereas the use of PCF with a suspended, solid core enables selective excitation of molecules in close proximity to the silica surface, through interaction with the evanescent field. We demonstrate the measurement of fluorescence spectra and fluorescence lifetimes in each of these excitation regimes and report the detection of attomole quantities of fluorescein.
14 citations
27 Oct 2013
TL;DR: In this paper, the authors report the successful fabrication of a ZBLAN photonic crystal fiber with sub-micron features and large air-filling fraction and use it to generate a 10dB-flat supercontinuum (350 to 2500nm) from 140fs, 1nJ pulses at 1042nm.
Abstract: We report the successful fabrication of a ZBLAN photonic crystal fiber with sub-micron features and large air-filling fraction and use it to generate a 10dB-flat supercontinuum (350 to 2500nm) from 140fs, 1nJ pulses at 1042nm.
4 citations
Posted Content•
TL;DR: In this paper, the authors introduce an extension of the Lugiato-Lefever model to describe the spatio-temporal evolution of arbitrary pulses propagating in a ring cavity and demonstrate spontaneous symmetry breaking as well as multistability regimes in a synchronously pumped fiber-ring cavity.
Abstract: We introduce a new equation that describes the spatio-temporal evolution of arbitrary pulses propagating in a fiber-ring cavity. This model is a significant extension of the traditionally used Lugiato-Lefever model. We demonstrate spontaneous symmetry breaking as well as multistability regimes in a synchronously pumped fiber-ring cavity. The equation can be applied to virtually any type of waveguide-based ring cavity.
2 citations
TL;DR: In this paper, the authors reported stimulated Raman-like optoacoustic generation of a 6 MHz optical frequency comb upon launching CW laser light into a 12 cm long evacuated dual-nanoweb fiber.
Abstract: We report stimulated Raman-like optoacoustic generation of a 6 MHz optical frequency comb upon launching CW laser light into a 12 cm long evacuated dual-nanoweb fibre. The threshold power is only a few mW.
2 citations
09 Jun 2013
TL;DR: In this article, the storage and retrieval of broadband optical pulses using a Raman interaction in a room-temperature ensemble of cesium atoms confined in a hollow-core photonic-crystal fiber was described.
Abstract: We report the storage and retrieval of broadband optical pulses using a Raman interaction in a room-temperature ensemble of cesium atoms confined in a hollow-core photonic-crystal fibre.
2 citations
28 Aug 2013
TL;DR: In this paper, optical activity in twisted six-fold symmetric solid-core PCF is studied. And the associated circular birefringence, which scales linearly with the twist rate, arises from a non-resonant geometrical effect that is linked to angular momentum.
Abstract: Recent results on optical activity in twisted six-fold symmetric solid-core PCF are discussed. The associated circular birefringence, which scales linearly with twist rate, arises from a non-resonant geometrical effect that is linked to angular momentum.
14 Apr 2013
TL;DR: In this paper, a recently discovered optothermal trapping mechanism based on optically induced thermal creep flow is discussed for laser propulsion of microparticles and red blood cells in hollow-core photonic crystal fiber.
Abstract: We review our work on laser propulsion of microparticles and red blood cells in hollow-core photonic crystal fiber. A recently discovered optothermal trapping mechanism based on optically induced thermal creep flow is discussed.
09 Jun 2013
TL;DR: In this paper, the emission of pressure-tunable ultra-violet dispersive waves into higher-order modes of a gas-filled kagome-PCF is experimentally and numerically demonstrated.
Abstract: The emission of pressure-tunable ultra-violet dispersive waves into higher-order modes of a gas-filled kagome-PCF is experimentally and numerically demonstrated. Numerical evidence of a balance between Kerr-driven self-focusing and plasma-defocusing is also presented.
12 May 2013
TL;DR: In this paper, the authors used a hydrogen-filled hollow core photonic crystal fiber (HC-PCF) as a host for gas-based nonlinear optical experiments, where the pump pulse duration is well below the period of one rotational cycle of ortho-hydrogen (57 fs), and the interaction takes place in the impulsive regime.
Abstract: Hollow-core photonic crystal fibre (HC-PCF) is unique host for gas-based nonlinear optical experiments. This is because it offers low-loss single-mode guidance in a micron-sized hollow core along with pressure-tunable dispersion and nonlinearity. In previous work, noble gases have been used as Raman-free nonlinear media, permitting efficient soliton-based pulse compression where the interplay between Kerr nonlinearity and anomalous dispersion results in dramatic self-compression of an ultrashort pulse. Novel phenomena such as UV wavelength conversion and even plasma generation from ~50 fs laser pulses of ~1 μJ energy have been reported [1]. In a different context, HC-PCF filled with molecular gases offers excellent performance as an ultra-low threshold modulator and frequency shifter for nano- and picosecond laser pulses [2]. Motivated by this, here we study experimentally and numerically the propagation of a 40 fs laser pulse in a hydrogen-filled HC-PCF [3]. Since the pump pulse duration is well below the period of one rotational cycle of ortho-hydrogen (57 fs), so that the bandwidth of the pulse is broader than the corresponding Raman frequency shift (18 THz), the interaction takes place in the impulsive regime. In other words, the pump pulse already contains Stokes shifted photons and the Raman process is self-seeded. Moreover, since the pulse duration is much shorter than the phase relaxation time T2 of the molecular coherence, the (Raman) response of the medium is highly non-instantaneous (i.e., nonlocal in time) and affected by the whole pre-history of the interaction [4].
TL;DR: In this article, spontaneous symmetry breaking can occur in a temporally inversion-symmetric system consisting of a photonic crystal fiber ring cavity synchronously pumped by ultrashort optical pulses.
Abstract: We show theoretically that spontaneous symmetry breaking can occur in a temporally inversion-symmetric system consisting of a photonic crystal fiber ring cavity synchronously pumped by ultrashort optical pulses.
12 Nov 2013
TL;DR: By filling the holes of microstructured optical fibers with particular materials, this paper implemented plasmonic fibers showing hybridized plasmoric excitations with a sophisticated near field polarization, spiralling plasoric modes and localized plasmanic resonances.
Abstract: By filling the holes of microstructured optical fibers with particular materials, we implement plasmonic fibers showing hybridized plasmonic excitations with a sophisticated near field polarization, spiralling plasmonic modes and localized plasmonic resonances.
28 Aug 2013
TL;DR: In this paper, the development of lead-silicate and fluoride-glass photonic crystal fibres was reported, which enabled the fabrication of both solid-and hollow-core fibres with unprecedented uniformity.
Abstract: We report recent progress in the development of lead-silicate and fluoride-glass photonic crystal fibres. Our improved drawing technique enables the fabrication of both solid- and hollow-core fibres with unprecedented uniformity.
12 May 2013
TL;DR: In this article, it was shown numerically that a fundamental soliton can cleanly blue-shift in the absence of any higher order nonlinear effects, and an all-fiber integrated device may be designed that allows tunable frequency up-conversion over an octave, combined with pulse compression.
Abstract: Gas-filled hollow-core photonic crystal fiber (HC-PCF) is an ideal vehicle for studying nonlinear fiber optics in gaseous media [1]. It combines the merits of conventional fibers (tight single-mode confinement over long distances) with the advantages of gases: pressure-controlled dispersion, absence of optical damage and transparency in extreme wavelength ranges. In the case of kagome-style HC-PCF, these features have permitted observation of highly efficient tunable deep-UV generation [2] and ionization-based nonlinear fiber optics [3,4]. In the latter case soliton self-compression produces intensities sufficient to partially ionize the filling gas (~1015 W/cm2), resulting in plasma-induced phase-modulation and a unique soliton self-frequency blue-shift. The initial dynamics of these phenomena are dominated by higher order soliton propagation and compression, followed by fission and the emission of multiple blue-shifting solitons. It has been predicted using perturbation theory, however, that fundamental solitons will self-frequency blue-shift in the absence of any higher order nonlinear effects [4]. In this paper we show numerically that a fundamental soliton can indeed cleanly blue-shift, and we go on to suggest how an all-fiber integrated device may be designed that allows tunable frequency up-conversion over an octave, combined with pulse compression.
12 Nov 2013
TL;DR: In this article, the authors review the recent results on hybrid chalcogenide-silica waveguides with the focus on nanotapers, band gap guidance and mid infrared super continuum generation.
Abstract: In my presentation I will review our recent results on hybrid chalcogenide-silica waveguides with the focus on nanotapers, band gap guidance and mid infrared super continuum generation.
TL;DR: In this paper, a coherent supercontinuum spanning 1.7-4 μm is generated in a chalcogenide-silica nano-spike waveguide pumped at 2 μm.
Abstract: A coherent supercontinuum spanning 1.7-4 μm is generated in a novel chalcogenide-silica nano-spike waveguide pumped at 2 μm. Interference with a doubly-resonant OPO proves coherence, and enables sub-Hz locking of the OPO to the pump.
12 May 2013
TL;DR: In this article, the authors explore numerically the differences between multi-cycle MI with a predicted soliton duration τ 0 > c/ λ ~2.7 fs, and subcycle MI τ 0 <; c/λ ~ 2.5 fs, with peak powers greater than 50 MW.
Abstract: Summary form only given. Modulation instability (MI) in Xe-filled kagome-style hollow core photonic crystal fibre (PCF) has recently been demonstrated experimentally using 500 fs laser pulses centred at λ = 800 nm with energies of a few μJ [1]. It is known that MI leads to the formation of fundamental solitons [2] with average amplitude and temporal width given by [3]: τ 0 = √2T 0 (ΠN), where T 0 is the duration of the input pulse, N = √(γP 0 T 0 /|β2|) the soliton order, γ the nonlinear coefficient, P0 the pump peak power and β 2 the group velocity dispersion. This means that τ 0 depends on N. The average temporal width of the solitons emerging from the instability can be arbitrarily set by suitable choice of gas pressure and pump pulse energy and duration. This theory is however only strictly valid within the approximations of the nonlinear Schrodinger equation; for few-cycle pulses a more complete model based on the full field equation must be used [4]. Using a statistical approach we explore numerically the differences between multi-cycle MI with a predicted soliton duration τ 0 > c/ λ ~2.7 fs, and sub-cycle MI τ 0 <; c/ λ ~2.7 fs. After running many simulations (~1000) for both cases we retrieve, at a given fibre position, the temporal location, duration and peak power of certain discrete peaks in the intensity envelope. For a predicted average soliton duration of 7 fs (multi-cycle regime) the simple analysis above works as expected (Fig. 1); N = 1 solitons are predominantly generated (dashed curve), the peak in the distribution of pulse durations being at 7 fs. Even after propagation over 3 dispersion lengths the distribution is maintained, as expected for solitons. The small deviations are likely to be due to higher order effects in these extremely short and broadband pulses.For a predicted average soliton duration of 1 fs, i.e., in the sub-cycle regime, we see that instead of an N = 1 distribution, the majority of pulses condense to a single state with duration 1.5 fs, two small distributions appearing along the N = 1 and N = 2 lines, corresponding respectively to half-cycle and single-cycle solitons (Fig. 2a). Upon propagation this state evolves , eventually converging to that in Fig. 2b. Remarkably, although the NLSE-based MI theory is not valid, MI-like break-up still occurs, leading to an incoherent train of pulses of duration 0.5 to 1.5 fs, with peak powers greater than 50 MW. A very broad supercontinuum is generated (Fig. 2c) and the numerical and experimental spectra agree extremely well, supporting the validity of the numerical model in this extreme case.
28 Aug 2013
TL;DR: By filling the holes of microstructured optical fibers with particular materials, this article implemented highly nonlinear chalcogenide-silica waveguides for mid-IR supercontinuum generation and plasmonic fibers showing hybridized plasmics excitations with a sophisticated near field polarization.
Abstract: By filling the holes of microstructured optical fibers with particular materials, we implement highly nonlinear chalcogenide-silica waveguides for mid-IR supercontinuum generation and plasmonic fibers showing hybridized plasmonics excitations with a sophisticated near field polarization.
09 Jun 2013
TL;DR: In this article, two schemes for multi-μJ pulse compression in noble gas-filled hollow-core kagome-PCF are demonstrated and compared and a fiber-plus-chirped-mirror combination compresses 150 fs, 9.5 μJ pulses to 26 fs, and soliton effect compression produces sub 7 fs pulses.
Abstract: Two schemes for multi-μJ pulse compression in noble-gas-filled hollow-core kagome-PCF are demonstrated and compared. A fiber-plus-chirped-mirror combination compresses 150 fs, 9.5 μJ pulses to 26 fs, and soliton-effect compression produces sub 7 fs pulses.