66 research outputs found
Dithering-based real-time control of cascaded silicon photonic devices by means of non-invasive detectors
No full textReal-time control of multiple cascaded devices is a key requirement for the development of complex silicon photonic circuits performing new sophisticated optical functionalities. This article describes how the dithering technique can be leveraged in combination with non-invasive light probes to independently control the working point of many photonic components. The standard technique is extended by introducing the concept of orthogonal dithering signals to simultaneously discriminate the effect of different actuators, while the idea of frequency re-use is discussed to limit the complexity of control systems in cascaded architectures. After a careful analysis of the problem, the article presents an automated feedback strategy to tune and lock photonic devices in the maxima/minima of their transfer functions with given response speed and sensitivity. The trade-offs of this approach are discussed in detail to provide guidelines for the design of the feedback loop. Experimental demonstrations on a mesh of Mach-Zehnder interferometers and on cascaded ring resonators are discussed to validate the proposed control architecture in different scenarios and applications
Automated Thermal Drift Compensation in WDM-based Silicon Photonic Multi-Socket Interconnect Systems
No full textWe present an on-chip AWGR-based interconnect system with automated thermal drift compensation along cascaded resonant structures in a dual-socket layout. Error-free operation in a 30 Gb/s data-routing scenario within a 12 °C temperature range is demonstrated
Reduction of rockfall risk of the Teleferik area of Santorini-Greece.
No full textΗ περιοχή της καλδέρας της Σαντορίνης, ανάντη του τελεφερίκ και του Παλαιού λιμένα Φηρών, χαρακτηρίζεται από υψηλό κατολισθητικό κίνδυνο λόγω των υφιστάμενων μορφολογικών, γεωλογικών, γεωτεχνικών και γεωδυναμικών συνθηκών. Δεδομένης της διέλευσης εκατοντάδων χιλιάδων τουριστών σε ετήσια βάση, γίνεται εύκολα αντιληπτή η αναγκαιότητα λήψης συγκεκριμένων μέτρων μείωσης του κινδύνου. Η έρευνα έχει ως στόχους: i)Την υπόδειξη περιοχών με αυξημένη πιθανότητα εκδήλωσης αποκολλήσεων βραχοτεμαχών ii) Tην υπόδειξη των όγκων στους οποίους θα πρέπει να γίνει άμεση παρέμβαση, iii) Την παρουσίαση σεναρίων κατολισθήσεων – καταπτώσεων, iv) Την υπόδειξη επειγόντων έργων ανάντη του κάτω Σταθμού του Τελεφερίκ προκειμένου να μειωθεί στο ελάχιστο δυνατό η επικινδυνότητα. Χρησιμοποιήθηκε γνωστό λογισμικό ανάλυσης καταπτώσεων, με το οποίο έγιναν ανάδρομες επιλύσεις και προσομοιώσεις σύμφωνα με τα στοιχεία από πρόσφατα φαινόμενα. Οι παρεμβάσεις εντάσσονται στο γενικότερο πλαίσιο των έργων μεγάλης κλίμακας, ενώ δίνεται ιδιαίτερη έμφαση στα προτεινόμενα επείγοντα έργα ανάντη του κάτω Σταθμού Τελεφερίκ, τα οποία θα λειτουργήσουν ως πρόσθετη δικλείδα ασφαλείας σε περίπτωση εκδήλωσης έντονων κατολισθητικών γεγονότων.The Teleferik area of Santorini Volcanic Complex, is characterized by rockfall risk due to existing morphological, geological, geotechnical and geodynamic conditions. It is therefore considered a high risk area because of the huge number, in annual base, of its visitors. The objects of the research are: (i) To identify areas with increased risk of boulders’ detachment, ii) The mapping of rockmasses for direct intervention projects,( iii)To suggest scenarios of rockfall events, (iv) To recommend the urgent works required upslope of the lower lift station of the Teleferik in order to reduce the existing risks to an utmost minimum. The calculations for the above assessments were mostly based on back analysis method, processing data of the recent rockfall events. The proposed interventions belong to the general context of large-scale projects, while top priority is given to works upslope of the lower lift station, which will work as an extra last line of defense in case of large-scale geodynamic events in the future
FIELD OBSERVATIONS OF THE 2015 (NOVEMBER 17, MW 6.4) LEFKAS (IONIAN SEA, WESTERN GREECE) EARTHQUAKE IMPACT ON NATURAL ENVIRONMENT AND BUILDING STOCK OF LEFKAS ISLAND
No full textOn Tuesday, November 17, 2015 at 07:10:07 (UTC) a strong earthquake struck Lefkas Island (Ionian Sea, Western Greece) with magnitude Mw 6.4, depth of about 7 km and epicenter located 20 km southwest of Lefkas town. The seismic activity in the region was essentially expected after the 2003 Lefkas earthquake and the 2014 Cephalonia earthquakes. Between these earthquake affected areas, the tectonic stresses were not released after the 1948 Lefkas earthquakes. Instead, they were intensifying and accumulating until the generation of the 2015 event. It was felt in Lefkas and the surrounding region and caused the death of 2 people, the injury of 8 others, earthquake environmental effects (EEE) and damage to buildings and infrastructure. Secondary EEE were observed in western Lefkas and included ground cracks, slope movements and liquefaction. Primary effects were not detected in the field. Buildings damage were mainly observed in villages of Dragano-Athani graben in southwestern Lefkas. Among structures constructed with no seismic provisions, the stone masonry buildings and monumental structures suffered most damage, while the traditional buildings with dual structural system performed relatively well. Reinforced-concrete buildings were affected not so much by the earthquake itself but by the generation of secondary effects.</jats:p
III-V/SOI photonic crystal nanolaser for high-speed wavelength conversion and memory operation
No full textWe experimentally demonstrate wavelength conversion and bit-level memory operation in a hybridly integrated III-V on SOI photonic crystal nanolaser with total footprint of 6.2μm2 and record-energy of 6.4fJ/bit, showing error-free operation at 5Gb/s.</p
FIELD OBSERVATIONS OF THE 2015 (NOVEMBER 17, MW 6.4) LEFKAS (IONIAN SEA, WESTERN GREECE) EARTHQUAKE IMPACT ON NATURAL ENVIRONMENT AND BUILDING STOCK OF LEFKAS ISLAND
No full textΤην Τρίτη 17 Νοεμβρίου 2015 στις 09:10:07 (τοπική ώρα) εκδηλώθηκε σφοδρή σεισμική δόνηση μεγέθους Mw 6.4, βάθους περί τα 7χλμ και με επίκεντρο σε απόσταση 20 χλμ νοτιοδυτικά της πόλης της Λευκάδας. Η σεισμική δραστηριότητα στην περιοχή ήταν ουσιαστικά αναμενόμενη σε μεσοπρόθεσμη κλίμακα μετά τον σεισμό της Λευκάδας το 2003 και τους σεισμούς της Κεφαλονιάς το 2014. Στον ενδιάμεσο χώρο οι γεωτεκτονικές δυνάμεις δεν είχαν εκτονωθεί μετά τους σεισμούς του 1948 με αποτέλεσμα την εκδήλωση του πρόσφατου σεισμού, που έγινε αισθητός σε όλη τη Λευκάδα και την ευρύτερη περιοχή προκαλώντας το θάνατο 2 και τον τραυματισμό 8 κατοίκων, εκτεταμένες δευτερογενείς επιπτώσεις στο περιβάλλον και βλάβες στα κτίρια και τις υποδομές του νησιού. Οι δευτερογενείς επιπτώσεις στη δυτική Λευκάδα διακρίθηκαν σε εδαφικές ρωγμές, αστοχίες πρανών και ρευστοποίηση. Πρωτογενείς επιπτώσεις δεν παρατηρήθηκαν. Κτιριακές βλάβες σημειώθηκαν κυρίως σε οικισμούς στο βύθισμα Δράγανου-Αθάνιου στη νοτιοδυτική Λευκάδα. Από τα κτίρια, που έχουν κατασκευαστεί χωρίς αντισεισμικό σχεδιασμό, τα πετρόκτιστα κτίρια και οι ιστορικές και μνημειακές κατασκευές υπέστησαν τις σοβαρότερες βλάβες, ενώ τα παραδοσιακά κτίρια με διπλό δομικό σύστημα ανάληψης φορτίων συμπεριφέρθηκαν ικανοποιητικά. Τα κτίρια με οπλισμένο σκυρόδεμα επηρεάστηκαν όχι τόσο από το σεισμό αλλά από τις δευτερογενείς επιπτώσεις του στο περιβάλλον.On Tuesday, November 17, 2015 at 07:10:07 (UTC) a strong earthquake struck Lefkas Island (Ionian Sea, Western Greece) with magnitude Mw 6.4, depth of about 7 km and epicenter located 20 km southwest of Lefkas town. The seismic activity in the region was essentially expected after the 2003 Lefkas earthquake and the 2014 Cephalonia earthquakes. Between these earthquake affected areas, the tectonic stresses were not released after the 1948 Lefkas earthquakes. Instead, they were intensifying and accumulating until the generation of the 2015 event. It was felt in Lefkas and the surrounding region and caused the death of 2 people, the injury of 8 others, earthquake environmental effects (EEE) and damage to buildings and infrastructure. Secondary EEE were observed in western Lefkas and included ground cracks, slope movements and liquefaction. Primary effects were not detected in the field. Buildings damage were mainly observed in villages of Dragano-Athani graben in southwestern Lefkas. Among structures constructed with no seismic provisions, the stone masonry buildings and monumental structures suffered most damage, while the traditional buildings with dual structural system performed relatively well. Reinforced-concrete buildings were affected not so much by the earthquake itself but by the generation of secondary effects
III-V-on-Si Photonic Crystal Nanocavity Laser Technology for Optical Static Random Access Memories
No full textHeterogeneous integration of III-V semiconductors on silicon has gained considerable momentum fueled by the need to implement fully functional photonic devices and circuits in a CMOS compatible platform. In this communication, we report on a III-V photonic crystal (PhC) nanocavity, heterogeneously integrated on a silicon-on-insulator platform, to form a PhC nanocavity laser capable of exhibiting two elementary static random access memory (SRAM) cell functions individually, namely switching and latching operations under a high-speed, bit-level regime. As such, the PhC nanocavity laser is examined as a generic logic functions building block, suitable toward multiGb/s energy-efficient, optical SRAM cells with minimal device footprint. The proposed device occupies a total area of only 6.2 μm2, rendering in this way the demonstrated memory element the smallest among the integrated optical memories presented so far. Bit-level SRAM cell operation requires two elementary functions: the access gate (AG) switching function and set-reset flip-flop (SR-FF) latching function. At first, AG switching operation is evaluated through successful wavelength conversion at 10 Gb/s, revealing a power penalty of 1 dB at 10-9 BER and a switching energy of only 4.8 fJ/bit. Then, fully functional SR-FF memory operation is successfully demonstrated, exhibiting error-free operation with negative power penalty at 5 Gb/s and switching energies of 6.4 fJ/bit. FF operation at higher speeds of 10 Gb/s with reduced switching energy levels of 3.2 fJ/bit is also experimentally investigated. Both logic operations were demonstrated separately with the same PhC nanocavity laser device exhibiting <50 ps switching times and evaluated under real-type data traffic patterns, raising expectations for beyond 20 Gb/s capabilities toward implementing energy-efficient, ultracompact and high-speed true optical SRAM setups for Datacom applications.</p
Opportunities and Obstacles of Monolithic III-V Integration on Silicon
No full textInternational audienceThe massive growth of data flux and the quest for energy sustainability definitely push the scientific community to reinvent the concept of microprocessor.[1] The International Technology Roadmap of Semiconductors forecasts the emergence of hybrid microprocessors where different information technology solutions will coexist on a single chip.[2] In particular, photonic on-chip interconnects have early been proposed to replace electric interconnects for links requiring large data transfer or simply to reduce routing-induced power losses. However, such a paradigm shift is still hindered by the efficient integration of laser sources within the microprocessor architecture.[3] While the group IV photonics community is still far from demonstrating a microscale electrically-driven laser source,[4] the III-V on Si bonding approach seems to progressively impose itself as the reference for the integration of a small number lasers.[5], [6] Recent publications[7], [8] show that a third approach may challenge the later: monolithic III-V integration on silicon. In this talk, we will discuss the potential of monolithic III-V integration on Si in the framework of on-chip information technologies as well as the technological obstacles that the scientific community should overcome. This analysis will be done from the physical level of individual components where performances, lifetimes and CMOS compatibility are the main criteria to the system level where architecture design, production issues and costs then enter into account.[1]D. A. B. Miller, “Device Requirements for Optical Interconnects to Silicon Chips,” Proc. IEEE, vol. 97, no. 7, pp. 1166–1185, Jul. 2009.[2]ITRS, “2013 Executive Summary.” 2013.[3]T. Baehr-Jones, T. Pinguet, P. Lo Guo-Qiang, S. Danziger, D. Prather, and M. Hochberg, “Myths and rumours of silicon photonics,” Nat. Photonics, vol. 6, no. 4, pp. 206–208, Apr. 2012.[4]Y. Takahashi, Y. Inui, M. Chihara, T. Asano, R. Terawaki, and S. Noda, “A micrometre-scale Raman silicon laser with a microwatt threshold,” Nature, vol. 498, no. 7455, pp. 470–474, Jun. 2013.[5]T. Alexoudi et al., “III–V-on-Si Photonic Crystal Nanocavity Laser Technology for Optical Static Random Access Memories,” IEEE J. Sel. Top. Quantum Electron., vol. 22, no. 6, pp. 1–10, Nov. 2016.[6]D. Liang, X. Huang, G. Kurczveil, M. Fiorentino, and R. G. Beausoleil, “Integrated finely tunable microring laser on silicon,” Nat. Photonics, vol. 10, no. 11, pp. 719–722, Sep. 2016.[7]S. Chen et al., “Electrically pumped continuous-wave III–V quantum dot lasers on silicon,” Nat Photon, vol. advance online publication, Mar. 2016.[8]Y. Wan et al., “Room Temperature CW 1.3 μm Single Mode Lasing of InAs Quantum Dot Micro-disk Lasers Grown on (001) Si,” in Conference on Lasers and Electro-Optics (2016), paper SM1G.3, 2016, p. SM1G.3
Ultra-compact III-V-on-Si photonic crystal memory for flip-flop operation at 5 Gb/s
No full textWe report on a photonic crystal (PhC) nanolaser based on the heterogeneous integration of a III-V PhC nanocavity on SOI, configured to operate as a Set-Reset Flip-Flop (SR-FF). The active layer is a nanobeam cavity made of a 650nm × 285nm InP-based wire waveguide evanescently coupled to 500nm × 220nm SOI wire waveguides, demonstrating a record-low footprint of only 6.2μm2. Injection locking enables optical bistability allowing for memory operation with only 6.4fJ/bit switching energies and <50ps response times. Bit-level SR-FF memory operation was evaluated at 5Gb/s with PRBS-resembling data patterns, revealing error free operation with a negative power penalty.</p
Evaluation of current therapeutic strategies in Behçet's disease
No full textBehçet's disease (BD) is a chronic relapsing vasculitis with multifunctional pathogenesis. The mucocutaneous and ocular lesions are the commonest manifestations, but BD also affects the musculoskeletal, intestinal, cardiac, and central nervous system. BD therapy is based on the suppression of the inflammatory process, using immunomodulating and immunosuppressive agents. In selected cases, invasive procedures may be required. © Clinical Rheumatology 2010
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