Study of Periodic and Quasi-Periodic Structures in Silicon-on-Insulator

In this thesis, a numerical design approach has been proposed and developed based on the transmission matrix method in order to characterize periodic and quasi-periodic photonic structures in silicon-on-insulator. The approach and its performance have been extensively tested with specific structures in 2D and its validity has been verified in 3D

Diversity and ethics in trauma and acute care surgery teams: results from an international survey

Background Investigating the context of trauma and acute care surgery, the article aims at understanding the factors that can enhance some ethical aspects, namely the importance of patient consent, the perceptiveness of the ethical role of the trauma leader, and the perceived importance of ethics as an educational subject. Methods The article employs an international questionnaire promoted by the World Society of Emergency Surgery. Results Through the analysis of 402 fully filled questionnaires by surgeons from 72 different countries, the three main ethical topics are investigated through the lens of gender, membership of an academic or non-academic institution, an official trauma team, and a diverse group. In general terms, results highlight greater attention paid by surgeons belonging to academic institutions, official trauma teams, and diverse groups. Conclusions Our results underline that some organizational factors (e.g., the fact that the team belongs to a university context or is more diverse) might lead to the development of a higher sensibility on ethical matters. Embracing cultural diversity forces trauma teams to deal with different mindsets. Organizations should, therefore, consider those elements in defining their organizational procedures. Level of evidence Trauma and acute care teams work under tremendous pressure and complex circumstances, with their members needing to make ethical decisions quickly. The international survey allowed to shed light on how team assembly decisions might represent an opportunity to coordinate team member actions and increase performance

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

APPLICATIONS OF COUPLED RESONATORS IN PHOTONIC INTEGRATED CIRCUITS

Progress in photonic integrated circuits (PICs) enables contemporary solutions that cover more and more technology areas, including optical networking, computing systems and sensing. The capabilities of PICs continuously enrich thanks to the introduction of new photonic circuit elements. Among them, Micro Ring Resonators (MMRs) receive particular interest because of their wide range of functional properties that can serve to implement, e.g., integrated wavelength routers, lasers and sensors. The interaction of two or more optical modes by cascading multiple resonators leads to more sophisticated photonic applications through manipulation of the resonances and consequent flexible modification of the spectrum. This dissertation investigates the potential benefits of a novel configuration of coupled resonators, which can act as photonic switching element, reflector and sensor. As opposed to previously reported coupled resonators, the proposed device consists of double MRRs that are indirectly coupled through a central bus waveguide and a crossing. This configuration, Indirectly Coupled Resonators (ICR), can carry out versatile photonic functions that are the subjects of the presented research. The studied devices were fabricated in two different integration technology platforms, the InP-membrane-on-silicon (IMOS) and Silicon-On-Insulator (SOI). The wavelength routing properties of ICR are first examined in the context of the next generation Reconfigurable Optical Add/Drop Multiplexer (ROADM) for implementing flexible optical networks in wavelength division multiplexing technology. As a result of non-reciprocal wavelength routing behaviour, the ICR based switching fabric can combine the Add and Drop functions in a single transponder aggregator and therefore introduce bidirectional communication in ROADM systems that can reduce circuitry cost. Furthermore, the scalability analysis of an ICR based wavelength router topology is presented and compared with the conventional topology (λ-router) used in photonic Network-on-Chip applications. According to the topological analysis, ICR based routers can reduce the number of resonators required to construct such networks up to ∼ 50%, as the number of connected ports increases. Then, the presented device is analysed considering its reflection properties. By performing phase synchronization of the two coupled resonators, it is possible to implement a wavelength reflector. The single wavelength reflection is experimentally demonstrated using the ICR fabricated in SOI technology. The critical conditions that exhibit such operational regimes are addressed. The measurements show that thermally detuned reflected wavelengths over a 37 nm of wavelength span can have very narrow bandwidths (∼ 50 pm), which correspond to quality factor of ∼ 30,000. Additionally, multiple wavelength reflections are also experimentally demonstrated by the racetrack ICR fabricated in IMOS technology. Finally, a novel optical sensing scheme based on ICR is proposed. The scheme can execute data extraction from the sensor via either resonance shifts or intensity enhancements in the spectra of sensing signal relative to the reference signal. Therefore, this scheme is referred to as differential optical sensing. The differential sensing can pave the way of performing sensor calibration on-chip via an integrated heater on reference resonator. The performance comparison between conventional single ring and ICR based sensing schemes obtained from a suitably developed analytical model is presented. Overall, the results presented in this thesis reveal the diverse capabilities of indirectly coupled resonators, mostly aiming at introducing a new building block for photonic integrated circuits.I continui progressi dell’ottica integrata e della fotonica consentono soluzioni alla avanguardia in campi di applicazione sempre più vasti. Le funzionalità dei Circuiti Fotonici Integrati (PIC) si arricchiscono continuamente grazie all'introduzione di nuovi elementi circuitali realizzati mediante dispositivi fotonici. Tra questi, i Risonatori ad Anello (Micro Ring Resonator - MMR) stanno suscitando un interesse particolare grazie alla loro vasta gamma di proprietà funzionali che possono servire per implementare, ad esempio, router, laser e sensori. L'interazione di queste funzionalità, ottenibile mediante la disposizione in cascata di più risonatori, porta ad applicazioni sempre più sofisticate, che sfruttano la manipolazione delle risonanze e la conseguente modifica flessibile dello spettro di trasmissione dei dispositivi così realizzati. Questa tesi propone un dispositivo innovativo basato su una particolare configurazione di risonatori accoppiati e ne analizza i potenziali benefici. Il dispositivo proposto può agire, a seconda della configurazione, come elemento di commutazione, come riflettore e come sensore. A differenza dei dispositivi proposti in letteratura basati su risonatori accoppiati direttamente, quello che viene presentato in questa tesi è costituito da una coppia di risuonatori interagenti in modo indiretto attraverso una guida d'onda. Questa topologia, definita come “Risonatori ad accoppiamento indiretto (Indirectly Coupled Resonators - ICR)”, grazie alla sua versatilità può svolgere funzionalità differenti, la cui indagine costituisce il tema portante di questa tesi. I dispositivi sviluppati in questi anni sono stati fabbricati utilizzando due piattaforme tecnologiche: InP-membrane-on-silicon (IMOS) e Silicon-On-Insulator (SOI). Il dispositivo proposto viene inizialmente analizzato quando configurato come router per reti ottiche flessibili (reti elastiche), in cui può essere impiegato come add/drop multiplexer riconfigurabile (ROADM). Grazie al comportamento non reciproco in lunghezza d’onda, questo dispositivo può combinare le funzioni di Add/Drop in un unico aggregatore bidirezionale. Viene poi presentata l’analisi della scalabilità e definita una tipologia di router per applicazioni nelle Network-on-chip ottiche. Secondo l'analisi topologica svolta in questa tesi, i router basati su topologie ICR possono ridurre fino al ∼ 50% il numero di risonatori necessari, a parità di numero di porte. Viene poi proposto l’utilizzo di tale dispositivo come riflettore ottenibile, a parità di topologia, eseguendo la sincronizzazione dei due risonatori. Le misure sono state effettuate con dispositivi fabbricati in tecnologia SOI e mostrano la possibilità di sintonizzare il riflettore in un range di lunghezze d’onda di 37 nm. Le riflessioni possono avere larghezze di banda molto strette (∼ 50 pm), corrispondenti ad un fattore di qualità di ∼ 30.000. La possibilità di ottenere riflessioni su lunghezze d’onda multiple è stata invece verificata utilizzando risonatori racetrack con raggi identici e fabbricati in tecnologia IMOS. Nell’ultima parte della tesi viene invece analizzato, attraverso l’utilizzo di modelli matematici, l’impiego di tale dispositivo in ambito sensoristico. Viene proposto uno schema di funzionamento differenziale, interrogabile in lunghezza d’onda ed in intensità. La tecnica differenziale impiegata consente l’esecuzione della calibrazione del dispositivo direttamente su chip, semplificando così la taratura dello stesso. Le prestazioni del sensore sono confrontate, attraverso modellizzazione numerica, con quelle di sensori risonanti convenzionali. I risultati presentati in questa tesi rivelano le molteplici proprietà dei risonatori accoppiati indirettamente, che possono dunque costituire un nuovo blocco funzionale per i circuiti integrati fotonici

Integrated Vivaldi plasmonic antenna for wireless on-chip optical communications

In this paper we propose a novel hybrid optical plasmonic Vivaldi antenna for operation in the standard C telecommunication band for wavelengths in the 1550 nm range. The antenna is fed by a silicon waveguide and is designed to have high gain and large bandwidth. The shape of the radiation pattern, with a main lobe along the antenna axis, makes this antenna suitable for point-to-point connections for inter- or intra-chip optical communications. Direct port-to-port short links for different connection distances and in a homogeneous environment have also been simulated to verify, by comparing the results of a full-wave simulation with the Friis transmission equation, the correctness of the antenna parameters obtained via near-to-far field transformation

Double Vivaldi antenna for wireless optical networks on chip

In this paper we present a double plasmonic Vivaldi antenna for on-chip optical wireless communication. The proposed antenna is a two-element broadside array fed by a silicon waveguide. The designs of the power splitter and of the hybrid Si-plasmonic coupler used for antenna excitation are described in detail. The array radiation characteristics are optimized through Finite Difference Time Domain simulations and the performance of a point-to-point link is evaluated. The proposed double Vivaldi array increases the gain of 3 dB with respect to a single antenna, improving the received power on a link of 6 dB when the double antenna is used for both transmitting and receiving sections

A Design Tool for Integrated Optical Segmented Waveguides

Simulation of 3D structures requires large memory and CPU time, which may then forbid realistic simulations of complex structures. Computational requirements can be dramatically reduced using the Transmission matrix T of the structure elements. The T matrix of the whole structure is in fact the product of the T matrices of the constituting elements. The model is proposed and tested in 2D with some specific examples. Possible critical points, such as radiation modes effects and multimode guided propagation are commented

Differential Optical Sensing through Coupled Micro Ring Resonators

We theoretically investigate the performance of a double micro ring resonator for integrated optical sensing applications. The transmission characteristics of the proposed device can be driven in two distinct operations by controlling the difference of the round-trip phase shifts of the coupled resonators. The enhancement of the limit of detection by a factor of 5.6 compared to a single micro ring based sensor is demonstrated. Beside the fact that the single and double ring based schemes have the same spectral wavelength sensitivity of 918 nm per refractive index unit, the latter scheme also supports the intensity interrogation which can be used for on-chip thermal noise compensation via integrated micro heaters