Characterization of integrated Bragg gratings in silicon-on-insulator

Silicon-on-insulator (SOI) is rapidly emerging as a very promising material platform for integrated photonics. As it combines the potential for optoelectronic integration with the low-cost and large volume manufacturing capabilities and they are already accumulate a huge amount of applications in areas like sensing, quantum optics, optical telecommunications and metrology. One of the main limitations of current technology is that waveguide propagation losses are still much higher than in standard glass-based platform because of many reasons such as bends, surface roughness and the very strong optical confinement provided by SOI. Such high loss prevents the fabrication of efficient optical resonators and complex devices severely limiting the current potential of the SOI platform. The project in the first part deals with the simple waveguides loss problem and trying to link that with the polarization problem and the loss based on Fabry-Perot Technique. The second part of the thesis deals with the Bragg Grating characterization from again the point of view of the polarization effect which leads to a better stop-band use filters. To a better comprehension a brief review on the basics of the SOI and the integrated Bragg grating ends up with the fabrication techniques and some of its applications will be presented in both parts, until the end of both the third and the fourth chapters to some results which hopefully make its precedent explanations easier to deal with.

Synthesis, characterization and catalytic performances of ruthenium-based catalysts for the acceptorless dehydrogenative coupling of butanol

A growing interest towards new sources of energy has led in recent years to the development of a new generation of catalysts for alcohol dehydrogenative coupling (ADC). This green, atom-efficient reaction is capable of turning alcohol derivatives into higher value and chemically more attractive ester molecules, and it finds interesting applications in the transformation of the large variety of products deriving from biomass. In the present work, a new series of ruthenium-PNP pincer complexes are investigated for the transformation of 1-butanol, one of the most challenging substrates for this type of reactions, into butyl butyrate, a short-chain symmetrical ester widely used in flavor industries. Since the reaction kinetics depends on hydrogen diffusion, the study aimed at identifying proper reactor type and right catalyst concentration to avoid mass transfer interferences and to get dependable data. A comparison between catalytic activities and productivities has been made to establish the role of the different ligands bonded both to the PNP binder and to the ruthenium metal center, and hence to find the best catalyst for this type of reaction.

Misurazione della Sostenibilità in Azienda. Approccio Quantitativo all'Analisi della Letteratura attraverso Bibliografic Coupling.

L'elaborato si impegna ad esporre i risultati derivanti da una revisione estensiva della letteratura riguardante le pratiche di misurazione della sostenibilità in azienda. Si è scelto un approccio al problema di impostazione bibliometrico, consistente in analisi statistiche di dati bibliografici ricavabili osservando le relazioni tra documenti. Si sono utilizzati strumenti di clustering per categorizzare la letteratura ed individuare le aree di maggior interesse potenziali per aziende che desiderino investire con successo nella sostenibilità. Come risultato, si è ottenuta una chiara identificazione delle principali tematiche che devono essere tenute in considerazione nell’affrontare valutazioni relative alla misurazione e valorizzazione dei concetti di sostenibilità e impatto ambientale in ambito aziendale. Il presente lavoro si presenta inoltre come guida metodologica per un approccio quantitativo alla revisione della letteratura, adattabile ed applicabile in maniera iterativa per un continuo monitoraggio del tema o per indagini in altri ambiti. Questa tesi si pone dunque come base per ricerche e analisi successive finalizzate alla comprensione della letteratura.