1,879 research outputs found
Hollow core fiber with an octave spanning bandgap
No full textWe thoroughly compare the out-of-plane bandgaps generated by three realistic two-dimensional lattices: a triangular and a square arrangement of holes and a triangular arrangement of rods. We demonstrate that, for any given hole diameter-to-pitch ratio d/Λ, the triangular arrangement of interconnected resonators generates the widest possible bandgap along the air line, and we propose a physical interpretation explaining these results. The design of a hollow core photonic bandgap fiber based on such a lattice and able to transmit light with sub-decibel-per-meter losses over an octave of frequencies is presented for the first time, to the best of our knowledge
Multimode nonlinear fibre optics: theory and applications
No full textOptical fibres have been developed as an ideal medium for the delivery of optical pulses ever since their inception (Kao & Hockham, 1966). Much of that development has been focused on the transmission of low-energy pulses for communication purposes and thus fibres have been optimised for singlemode guidance with minimum propagation losses only limited by the intrinsic material absorption of silica glass of about 0.2dB/km in the near infrared part of the spectrum (Miya et al., 1979). The corresponding increase in accessible transmission length simultaneously started the interest in nonlinear fibre optics, for example with early work on the stimulated Raman effect (Stolen et al., 1972) and on optical solitons (Hasegawa & Tappert, 1973). Since the advent of fibre amplifiers (Mears et al., 1987), available fibre-coupled laser powers have been increasing dramatically and, in particular, fibre lasers now exceed kW levels in continuous wave (cw) operation (Jeong et al., 2004) and MW peak powers for pulses (Galvanauskas et al., 2007) in all-fibre systems. These developments are pushing the limits of current fibre technology, demanding fibres with larger mode areas and higher damage threshold. However, it is increasingly difficult to meet these requirements with fibres supporting one single optical mode and therefore often multiple modes are guided. Non-fibre-based laser systems are capable of delivering even larger peak powers, for example commercial Ti:sapphire fs lasers now reach the GW regime. Such extreme powers cannot be transmitted in conventional glass fibres at all without destroying them (Gaeta, 2000), but there is a range of applications for such pulses coupled into hollow-core capillaries, such as pulse compression (Sartania et al., 1997) and high-harmonic generation (Rundquist et al., 1998). For typical experimental parameters, these capillaries act as optical waveguides for a large number of spatial modes and modal interactions contribute significantly to the system dynamics.In order to design ever more efficient fibre lasers, to optimise pulse delivery and to control nonlinear applications in the high power regime, a thorough understanding of pulse propagation and nonlinear interactions in multimode fibres and waveguides is required. The conventional tools for modelling and investigating such systems are based on beam propagation methods (Okamoto, 2006). However, these are numerically expensive and provide little insight into the dependence of fundamental nonlinear processes on specific fibre properties, e.g., on transverse mode functions, dispersion and nonlinear mode coupling. For such an interpretation a multimode equivalent of the nonlinear Schrodinger equation, the standard and highly accurate method for describing singlemode nonlinear pulse propagation (Agrawal, 2001; Blow & Wood, 1989), is desirable. In this chapter, we discuss the basics of such a multimode generalised nonlinear Schrodinger equation (Poletti & Horak, 2008), its simplification to experimentally relevant situations and a few select applications. We start by introducing and discussing the theoretical framework for fibres with χ(3) nonlinearity in Sec. 2. The following sections are devoted to multimode nonlinear applications, presented in the order of increasing laser peak powers. A sample application in the multi-kW regime is supercontinuum generation, discussed in Sec. 3. Here we demonstrate how fibre mode symmetries and launching conditions affect intermodal power transfer and spectral broadening. For peak powers in the MW regime, self-focusing effects become significant and lead to strong mode coupling. The spatio-temporal evolution of pulses in this limit is the topic of Sec. 4. Finally, at GW peak power levels, optical pulses can only be delivered by propagation in gases. Still, intensities become so high that nonlinear effects related to ionisation must be taken into account. An extension of the multimode theory to include these extreme high power effects is presented in Sec. 5 and the significance of mode interaction is demonstrated by numerical examples pertaining to a recent experiment. Finally, we end this chapter with conclusions in Sec. 6
Characterization of Gaussian quantum Markov semigroups
No full textWe give a characterization of QMSs on the Bosonic Fock Space Gamma(C-d) whose predual preserves the set of gaussian states. We show they can be obtained via certain generalized GKLS generators and they satisfy an explicit formula for their action on Weyl operators
Comprendere il Reg. UE 2016/679: un'introduzione
No full textIl contributo analizza lo scenario e l’intento del Reg. UE 2016/679 in materia di protezione dei dati personali e il suo cambio di passo rispetto alla direttiva 95/46/CE. La risposta fornita dall'UE ad un problema complesso, accentuato dalla pervasività della tecnologia, viene analizzata con specifico riguardo ai principi di Accountability e di Compliance. In particolare si evidenzia come l'adeguamento al GDPR, per la mancata previsione di specifiche o aprioriostiche misure, realizzi una “procedimentalizzazione” dell’attività di adeguamento al GDPR imposto al titolare del trattamento dei dati personali, accentuata dall'entrata in vigore del d.lgs. n. 101/2018. Il compito dell'interprete, che ha già evidenziato i limiti che il GDPR presenta, è quello di prospettare una circolazione inevitabile dei dati personali nella quale la tutela dei diritti sia effettivamente garantita
Dataset for article: Polarization stable hollow core fiber interferometer with Faraday rotator mirrors
No full textThis dataset supports the publication:
R. SLAVIK, D. DOUSEK, D. SUSLOV, M. KOMANEC. S. ZVANOVEC, F. POLETTI, AND D.J. RICHARDSON, Polarization stable hollow core fiber interferometer with Faraday rotator mirrors, PHOTONICS TECHNOLOGY LETTERS 2021 </span
On irreducibility of Gaussian quantum Markov semigroups
No full textThe generator of a Gaussian quantum Markov semigroup on the algebra of bounded operator on a d-mode Fock space is represented in a generalized GKLS form with an operator G quadratic in creation and annihilation operators and Kraus operators L1,... ,Lm linear in creation and annihilation operators. Kraus operators, commutators |G,L-l| and iterated commutators |G, |G,L-l||, horizontal ellipsis up to the order 2d - m, as linear combinations of creation and annihilation operators determine a vector in DOUBLE-STRUCK CAPITAL C-2d. We show that a Gaussian quantum Markov semigroup is irreducible if such vectors generate DOUBLE-STRUCK CAPITAL C-2d, under the technical condition that the domains of G and the number operator coincide. Conversely, we show that this condition is also necessary if the linear space generated by Kraus operators and their iterated commutator with G is fully non-commutative
Dataset: Angle-spliced SMF to hollow core fiber connection with optimized back-reflection and insertion loss
No full textThis dataset supports the manuscript submitted to Journal of Lightwave Technology:
Cong Zhang, E. N. Fokoua, S. Fu, M. Ding, F. Poletti, D. J. Richardson, and R. Slavík
Angle-spliced SMF to hollow core fiber connection with optimized back-reflection and insertion loss. The dataset consists of an uploaded Archive (RAR) folder which includes 5 data files in Excel format.</span
Non c'è due senza tre: torna alle Sezioni Unite la questione dei caratteri fondanti la connessione teleologica
No full textIndividuazione del profitto e accertamento del fumus nel sequestro preventivo nei confronti dell'ente
No full textThe Decoherence-Free Subalgebra of Gaussian Quantum Markov Semigroups
No full textWe demonstrate a method for finding the decoherence-free subalgebra N(T) of a Gaussian quantum Markov semigroup on the von Neumann algebra B(Gamma(C-d)) of all bounded operator on the Fock space Gamma(C-d) on C-d. We show that N(T) is a type I von Neumann algebra L-infinity (R-dc;C)(circle times) over barB(Gamma(C-df)) determined, up to unitary equivalence, by two natural numbers d(c), d(f) <= d. This result is illustrated by some applications and examples
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