198,709 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
Wavelength conversion in a short length of a solid lead-silicate fibre
No full textWe experimentally demonstrate a four-wave-mixing-based wavelength conversion scheme at 1.55 µm using a 1.1-m length of highly nonlinear, dispersion tailored W-type lead–silicate optical fibe
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
Dataset supporting the publication "End-capping hollow-core fibers with suppressed coupling into higher-order modes"
No full text*This dataset supporting the publication:
Zhong, A., Ding, M., Numkam Fokoua, E., Zvanovec, S., Poletti, F., Komanec, M., & Slavík, R. (in press). End-capping hollow-core fibers with suppressed coupling into higher-order modes. IEEE Journal of Selected Topics in Quantum Electronics.
https://doi.org/10.1109/JSTQE.2024.3381797</span
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
The cognitive mobilization of organizational participation : missing evidence from Italy (1972-2006)
No full textThe Cognitive Mobilization thesis (CM) claims that the increasing educational levels in post-industrial societies bring about changes in the relationship between people's education and their participatory behaviour compared to the past. Younger, well-educated and more politically interested citizens are less likely to participate in political parties than poorly educated citizens, but more likely to join unconventional types of activist organisations. Using Italy as a test case, this study looks at whether the CM mechanism ought to be considered as a key factor shaping organizational participatory trends over time. Contrary to the CM thesis, we find that the highly educated continue to participate the most in political parties and that the gap between well and poorly educated in terms of their participation in activist associations does not become larger compared to the past
La forma del mondo
No full textProgetto per le Latomie dei Cappuccini di Siracusa.
Il progetto è stato elaborato nell’ambito delle attività disciplinari del Dottorato di Ricerca in Composizione Architettonica – Scuola di Dottorato in Ingegneria Civile ed Architettura – XXI ciclo – attivato presso la Facoltà di Architettura “Aldo Rossi” (docenti del gruppo di progettazione: Francesco Gulinello, Elena Mucelli, Stefania Rossl, Annalisa Trentin; dottorandi: Claudia Cagneschi, Roberto Fabbri, Giovanni Poletti, Raffaella Sacchetti. Hanno partecipato alla redazione degli elaborati per la mostra: Letizia Biondi, Valentina Graziani, Lorena Pulelli, Antonella Salvatori)
Il codice del terzo settore- Costituzione e forme organizzative
No full textIl contributo esamina l'assetto strutturale degli enti del Terzo settore, analizzando gli enti "tipici", quelli "atipici" e quelli "doppiamente atipici", ma rilevando la crescente neutralità della forma organizzativa. Si diffonde poi sul nuovo modo di acquisto della personalità giuridica delle associazioni e fondazioni del TS
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