Thermal noise and optomechanical features in the emission of a membrane-coupled compound cavity laser diode

We demonstrate the use of a compound optical cavity as linear displacement detector, by measuring the thermal motion of a silicon nitride suspended membrane acting as the external mirror of a near-infrared Littrow laser diode. Fluctuations in the laser optical power induced by the membrane vibrations are collected by a photodiode integrated within the laser, and then measured with a spectrum analyzer. The dynamics of the membrane driven by a piezoelectric actuator is investigated as a function of air pressure and actuator displacement in a homodyne configuration. The high Q-factor ($\sim 3.4\cdot 10^4$ at $8.3 \cdot 10^{-3}$ mbar) of the fundamental mechanical mode at $\sim 73$ kHz guarantees a detection sensitivity high enough for direct measurement of thermal motion at room temperature ($\sim 87$ pm RMS). The compound cavity system here introduced can be employed as a table-top, cost-effective linear displacement detector for cavity optomechanics. Furthermore, thanks to the strong optical nonlinearities of the laser compound cavity, these systems open new perspectives in the study of non-Markovian quantum properties at the mesoscale

Atomic gallium laser spectroscopy with violet/blue diode lasers

We describe the operation of two GaN-based diode lasers for the laser spectroscopy of gallium at 403 nm and 417 nm. Their use in an external cavity configuration enabled the investigation of absorption spectroscopy in a gallium hollow cathode. We have analyzed the Doppler broadened profiles accounting for hyperfine and isotope structure and extracting both the temperature and densities of the neutral atomic sample produced in the glow discharge. We have also built a setup to produce a thermal atomic beam of gallium. Using the GaN-based diode lasers we have studied the laser induced fluorescence and hyperfine resolved spectra of gallium.Comment: 10 pages, 7 figure

Digital Preservation, Archival Science and Methodological Foundations for Digital Libraries

Digital libraries, whether commercial, public or personal, lie at the heart of the information society. Yet, research into their long‐term viability and the meaningful accessibility of their contents remains in its infancy. In general, as we have pointed out elsewhere, ‘after more than twenty years of research in digital curation and preservation the actual theories, methods and technologies that can either foster or ensure digital longevity remain startlingly limited.’ Research led by DigitalPreservationEurope (DPE) and the Digital Preservation Cluster of DELOS has allowed us to refine the key research challenges – theoretical, methodological and technological – that need attention by researchers in digital libraries during the coming five to ten years, if we are to ensure that the materials held in our emerging digital libraries are to remain sustainable, authentic, accessible and understandable over time. Building on this work and taking the theoretical framework of archival science as bedrock, this paper investigates digital preservation and its foundational role if digital libraries are to have long‐term viability at the centre of the global information society.

Indexing, browsing and searching of digital video

Video is a communications medium that normally brings together moving pictures with a synchronised audio track into a discrete piece or pieces of information. The size of a “piece ” of video can variously be referred to as a frame, a shot, a scene, a clip, a programme or an episode, and these are distinguished by their lengths and by their composition. We shall return to the definition of each of these in section 4 this chapter. In modern society, video is ver

Learning from Digital Library Evaluations

In this paper we analyse evaluation studies of the Europeana digital library from its launch in 2009 until today. Using Saracevic’s digital library evaluation framework, the studies are categorised by their constructs, contexts, criteria, and methodologies. Concentrating on studies that evaluate Europeana services or single components, we show gaps in the evaluation of certain Europeana aspects. Finally, we derive strategies for building an evaluation archive that serves as memory and supports comparisons.Im vorliegenden Artikel analysieren wir Evaluationsstudien der digitalen Bibliothek Europeana von 2009 bis heute. Unter Berücksichtigung von Saracevic’ Evaluationsframework für digitale Bibliotheken werden die Studien nach ihren Konstrukten, Kontexten, Kriterien und Methodologien kategorisiert. Die Analyse konzentriert sich auf Studien, die Dienstleistungen oder einzelne Komponenten von Europeana evaluieren, und zeigt Lücken in der Evaluation bestimmter Aspekte von Europeana auf. Schließlich werden Strategien diskutiert, um ein Evaluationsarchiv zu entwickeln, welches sowohl der Langzeitarchivierung dient als auch Vergleiche von Evaluationsergebnissen unterstützt.Peer Reviewe

Innovative learning models for prisoners

Prison education should be a top priority issue in most societies. Prison conditions must not infringe human rights and dignity and must offer meaningful treatment programmes in order to support inmates in their rehabilitation and reintegration in society. The use of ICTs within a penitentiary context plays a crucial role in that. The present Volume looks at the learning potential in prisons and reports on innovative (e-)learning pathways for basic skills education as designed and tested in Cyprus, Greece, Italy and Romania. Research investigated on what counts as ‘educational’ in such a complex context and how to combine relevant pieces in a ‘learning mosaic’ (the broad range of any learning opportunity across it). This Volume argues that such an approach may be adopted in a wider European perspective within the frame of dynamic security