Phase-Change Meta-Devices for Tuneable Bandpass Filtering in the Infrared

Tuneable light filters, especially those which are compact and fast to tune, are essential in a wide range of technologies, especially for multispectral imaging applications. However, state-of-the-art approaches to create such filters all possess drawbacks, with many wavelength regions poorly served. This thesis attempts to address this problem by combining metasurfaces which support extraordinary optical transmission (ultra-thin band-pass filters) with chalcogenide phase-change materials (adding dynamic tuneability). The optical properties of phase-change materials are very different in their amorphous and crystalline states and switching between such states can be rapidly controlled via thermal excitations. In this work nine different phase-change materials, including alloys of GeTe, GeSbTe, GeSbSeTe and GaLaS, were optically and elementally characterised and assessed for their application-specific suitability. The resulting materials data was used to computationally design and evaluate a range of tuneable infrared filter device designs both optically and thermally. These filters exhibit high transmission (≈80% at best) with large spectral tuning ranges of approximately +50% relative to their shortest wavelength; this range is sufficient to cover entire atmospheric transmission windows. This is the first such combination of phase-change materials and extraordinary optical transmission for application from the visible through to long-wave infrared (14 μm) regions of the spectrum. A rigorous computational study was conducted to produce comprehensive design guidelines for such filters, and confirm the viability of in-situ electrical switching. Several filter devices were experimentally fabricated, and the viability for a number of applications, including tuneable filtering, chemical sensing and infrared displays, was investigated and confirmed computationally.Engineering and Physical Sciences Research Council (EPSRC

Low Power Memory/Memristor Devices and Systems

This reprint focusses on achieving low-power computation using memristive devices. The topic was designed as a convenient reference point: it contains a mix of techniques starting from the fundamental manufacturing of memristive devices all the way to applications such as physically unclonable functions, and also covers perspectives on, e.g., in-memory computing, which is inextricably linked with emerging memory devices such as memristors. Finally, the reprint contains a few articles representing how other communities (from typical CMOS design to photonics) are fighting on their own fronts in the quest towards low-power computation, as a comparison with the memristor literature. We hope that readers will enjoy discovering the articles within

Microarchitectures pour la sauvegarde incrémentale, robuste et efficace dans les systèmes à alimentation intermittente

Embedded devices powered with environmental energy harvesting, have to sustain computation while experiencing unexpected power failures.To preserve the progress across the power interruptions, Non-Volatile Memories (NVMs) are used to quickly save the state. This dissertation first presents an overview and comparison of different NVM technologies, based on different surveys from the literature. The second contribution we propose is a dedicated backup controller, called Freezer, that implements an on-demand incremental backup scheme. This can make the size of the backup 87.7% smaller then a full-memory backup strategy from the state of the art (SoA). Our third contribution addresses the problem of corruption of the state, due to interruptions during the backup process. Two algorithms are presented, that improve on the Freezer incremental backup process, making it robust to errors, by always guaranteeing the existence of a correct state, that can be restored in case of backup errors. These two algorithms can consume 23% less energy than the usual double-buffering technique used in the SoA. The fourth contribution, addresses the scalability of our proposed approach. Combining Freezer with Bloom filters, we introduce a backup scheme that can cover much larger address spaces, while achieving a backup size which is half the size of the regular Freezer approach.Les appareils embarqués alimentés par la récupération d'énergie environnementale doivent maintenir le calcul tout en subissant des pannes de courant inattendues. Pour préserver la progression à travers les interruptions de courant, des mémoires non volatiles (NVM) sont utilisées pour enregistrer rapidement l'état. Cette thèse présente d'abord une vue d'ensemble et une comparaison des différentes technologies NVM, basées sur différentes enquêtes de la littérature. La deuxième contribution que nous proposons est un contrôleur de sauvegarde dédié, appelé Freezer, qui implémente un schéma de sauvegarde incrémentale à la demande. Cela peut réduire la taille de la sauvegarde de 87,7% à celle d'une stratégie de sauvegarde à mémoire complète de l'état de l'art. Notre troisième contribution aborde le problème de la corruption de l'état, due aux interruptions pendant le processus de sauvegarde. Deux algorithmes sont présentés, qui améliorent le processus de sauvegarde incrémentale de Freezer, le rendant robuste aux erreurs, en garantissant toujours l'existence d'un état correct, qui peut être restauré en cas d'erreurs de sauvegarde. Ces deux algorithmes peuvent consommer $23\%$ d'énergie en moins que la technique de ``double-buffering'' utilisée dans l'état de l'art. La quatrième contribution porte sur l'évolutivité de notre approche proposée. En combinant Freezer avec des filtres Bloom, nous introduisons un schéma de sauvegarde qui peut couvrir des espaces d'adressage beaucoup plus grands, tout en obtenant une taille de sauvegarde qui est la moitié de la taille de l'approche Freezer habituelle

A Future for Energy Innovation

Energise! shifts debate on energy/climate away from the usual opponents – climate sceptics vs those who focus on consumer demand and the consumer creation of CO2. Instead, it begins from the world’s need for much more cheap and clean energy. Energise! also focuses on the sociology of energy, analysing concepts such as consumer greed, ‘addiction’ to oil, uncertainty in climate science, the Precautionary Principle and resource wars.People shouldn't feel guilty about your carbon footprint. The way to deal with global warming is to build a bigger, better energy supply – not to change behaviour at home and in the car. People are not addicted to energy, and there's still time to fix global warming without downgrading lifestyles

1995 BRAC Commission

DoD Depot - Army Basing Study - Alternative Documentation Set; COBRA; Economic Impact. Box 269, XS-004