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Quantum technologies containing key GaN laser components will enable a new generation of high precision quantum sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the u.v. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for optical clocks and cold-atom interferometry systems. This includes the [5s2S1/2-5p2P1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s21S0-5p1P1] cooling transition in neutral strontium clocks at 461 nm and the [5s2s1/2 – 6p2P3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.

This work does not contain a single thesis as such, but presents five essays in the field of studies in architectural history and theory. The essays are intended to form a set around the theme of the deployment of concepts drawn from the work of Michel Foucault. The thesis does not offer to introduce Foucault's work, to undertake a general evaluation of it, nor to present all the ways in which Foucault might interest architects. (#1) A similar liberty is taken with the work of Manfredo Tafuri and with the various concepts of utopia which each writer uses. Indeed there is no intention to provide completed images of Foucault, Tafuri or of utopia in this thesis. The three figures consitute a body of positions and concepts which are used in the writing of the essays.The essays are intended to be theoretical works in architectural studies rather than to be a thoery in themselves. Thus Foucault provides more of a theme, a framework and a means, than an object of study. The subjects of the essays are partly selected so as to explore theoretical approaches at a number of levels. The essays do not rely upon being read in sequence but are organised from the most general concerns to the most particular. The 'Introduction' consists largely of remarks on the nature of architectural history, Foucault's 'theory' and the centrality of the concept of utopia, as an argument for my approach to Foucault.'Foucault and Tafuri' broaches some of the issues of historiography and attempts to position possibliities for Foucauldian intervention within a critique of Manfredo Tafuri's work. Questions asked are: what are the tasks of historical analysis, and what is the historical object?'The City, Ideology and The FamilyUtopia' is a study of architectural concepts emerging from the history of architecture's social deployment. The essay takes Tafuri's remarks as to the ideological function of the city and of Architecture and examines this possibility in the case of the position of the Family in le Corbusier's urban designs.'Heterotopia and the Architecture of the City' is a presentation of Foucault's concept of 'heterotopia' as it might be used to explore ideas from Aldo Rossi's work. As such the essay is addressed to the use of historical concepts in architectural practise. Tafuri's criticisms of Rossi and Foucault are considered.'Inside and Outside the Separate System' is an examination of a utopian attempt to establish a building type. The Separate System was a plan for prison design and management which constitutes the architectural deployment of the idea of discipline Foucault traces in Discipline-and-Punish (1976)'The Panopticon and the Theatre' is a study of a particular building design, the Panopticon prison of Jeremy Bentham. The essay traces a possible architectural history of the Panopticon, in part as an exploration of the different tasks of Foucault and an architectural historian.Bibliographies and notes to the text are presented at the end of each essay. Notes are indicated in the text thus- (#00). The sources of illustrations are given thus- (Evans 1978a), referring to that work in the bibleography.

Quantum based devices offer distinct advantages over conventional technology, such as improved sensitivity for sensing applications or enhanced accuracy for metrology. To utilize this potential, a number of technical requirements must be met, such as the cooling and trapping of neutral atoms for their use as quantum systems. We present our work on InGaN-based semiconductor cooling lasers for a variety of atomic species such as strontium, magnesium and ytterbium whos target wavelength was met by quantum-well composition engineering. Results on growth-epitaxy, facet coating as well as different configurations such as ECDL and MOPAs are presented, depending on the requirement of the application.

We report on GaN lasers with extremely narrow linewidth (~1MHz) at ‘magic wavelengths’ for cold-atom interferometry quantum sensors, using extended cavity GaN laser diodes and DFB GaN laser diodes.

Transport refrigeration units (TRUs) powered by integral diesel engines provide necessary temperature control for temperature-sensitive freight. TRU engines on trucks or trailers run while parked for temperature control (known as idling)—commonly for 40 to 60% of engine run time while at a home base distribution center. TRU engine idling is a sizable source of fuel consumption, causing air pollution, negative health effects, noise, and unnecessary cost. Electrification is a viable alternative to engine idling in TRUs parked at distribution centers, cold storage warehouses, truck stops, public rest areas, packing houses, terminals and other goods-movement facilities by adopting plug-in electric transport refrigeration units (eTRUs) with grid-supplied electricity. While electrification promises environmental and economic advantages over engine idling, adoption of eTRUs with grid-supplied electricity in the United States is slow. This paper presents results from a U.S. Environmental Protection Agency technical assistance pilot project to address market and behavior barriers of electrification of transport refrigeration to reduce TRU idling. The project findings revealed fleets often underestimate idling time and cost, while being skeptical about the long-term savings and benefits of electrification. The paper introduces a technical assistance approach to work with businesses to reduce operating costs while also reducing greenhouse gas emissions and toxic air pollution of temperature-controlled freight.

The number of public bikeshare systems has been increasing rapidly across the United States over the past 5 to 10 years. To date, most academic research around bikeshare systems in the United States has focused on the logistics of planning and operationalizing successful systems. Investigations of system users and effects on the local community are less common, and studies that are focused on efforts to engage underserved communities in bikeshare systems are rarer still. This paper relies on a survey of representatives from 56 U.S. bikeshare systems to better understand and document current approaches toward serving low-income and minority populations. The survey asked about equity policies and metrics, the degree to which equity considerations affect a variety of system practices, what the existing barriers to utilizing bikeshare are for target populations, and what challenges the bikeshare system entity faces in addressing those barriers. Results indicate that nearly one in four bikeshare systems has written policies around equity; nearly half of bikeshare systems with more than 500 bikes have such policies. However, many more systems consider equity in various aspects of their systems. Equity considerations affected station siting, fee structure and payment systems, and promotion and marketing in a majority of systems (68%, 72%, and 57%, respectively), and operations and data collection and analysis, though to a lesser extent (42% each). Bikeshare systems reported cost, access, and outreach as the largest barriers to equity, in addition to overall funding and staff levels.

Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the U.V. to the visible. We report our latest results on a range of AlGaInN diode-lasers targeted to meet the linewidth, wavelength and power requirements suitable for quantum sensors such as optical clocks and cold-atom interferometry systems. This includes the [5s2S1/2-5p2P1/2] cooling transition in strontium+ ion optical clocks at 422 nm, the [5s21S0-5p1P1] cooling transition in neutral strontium clocks at 461 nm and the [5s2s1/2 – 6p2P3/2] transition in rubidium at 420 nm. Several approaches are taken to achieve the required linewidth, wavelength and power, including an extended cavity laser diode (ECLD) system and an on-chip grating, distributed feedback (DFB) GaN laser diode.

Quantum technologies containing key GaN laser components will enable a new generation of precision sensors, optical atomic clocks and secure communication systems for many applications such as next generation navigation, gravity mapping and timing since the AlGaInN material system allows for laser diodes to be fabricated over a wide range of wavelengths from the u.v. to the visible.

consumption and financial burden of the multiple light sources required for such systems. The AlGaInN material system allows for single transverse mode laser diodes to be fabricated with optical powers up to 100 mW over a wide range from ~380 nm up to ~530 nm. By tuning the indium content and thickness of the GaInN quantum well, we have developed a range of AlGaInN diode-lasers targeted to meet the wavelength and power requirements suitable for optical clocks and atom interferometry systems. One of the major limiting factors in nitride laser diode development has been the lack of a suitable low defectivity and uniform GaN substrate. Recently, single crystal growth of large area, very low dislocation-density and uniform GaN substrates are grown using a combination of high temperature and high pressure enabling a range of AlGaInN laser technology to be developed. This direct light generation at the required wavelength is crucial to reduce complexity and size of the overall system, and to ensure a high wall-plug efficiency that is critical for space and mobile applications. We will present our development of GaN based, low SWaP, frequency-stabilised external-cavity seed and tapered amplifiers to operate at 461nm for first stage strontium cooling. This includes growth of custom optimised GaN epitaxy for operation at 461 nm, a robust ECDL geometry, a novel tapered amplifier design and important work in characterising the optical performance and minimising surface reflectivity to identify suitable working parameters.

Systems with the ability to observe and manipulate individual quantum states have been brought to applications that include among others satellite-free navigation and high-precision gravimetric sensing. Fundamentally, the applicability of quantum technology is limited by the complexity and financial burden of light sources required for such systems. These sources need to feature high optical power combined with compromised beam quality and frequency-stabilized narrow-linewidths. These parameters directly influence the performance of the quantum technology measurement system. Semiconductor devices are able to provide high brightness over broad spectral regions through band-gap engineering. InGaN-based laser sources can be engineered to operate from 380nm to 530 nm. This aligns well with the transitions of atomic species such as strontium, magnesium and ytterbium. However, a challenge remains to offer the narrow-linewidths ( 100 mW) required for many of these applications. We will present our development of GaN based narrow-linewidth seed and tapered amplifiers to operate at 461nm for first stage strontium cooling. This includes growth of custom optimised GaN epitaxy for operation at 461 nm, a robust ECDL geometry, a novel tapered amplifier design and important work in characterising and minimising the surface reflectivity to identify suitable working parameters. A comprehensive characterization of the device will be presented.

Picturesque is a term which owes part of its historical success to its ambiguity, signifying both an origin of subjectivist aesthetics and a popular naïve taste for the rustic. For historians of art and architecture this ambiguity is ramified by an issue of translation between ‘picturesque’ and its usual equivalent in German, 'malerisch'. In Heinrich Wölfflin’s influential account of the history of art since the Renaissance, 'Kunstgeschichtliche Grundbegriffe' (1915), he systematized 'das Malerische' as a formal value in dialectic with ‘the linear’. He defined the art historical 'malerisch' by contrasting it with the belief of naïve observers that picturesqueness was a property of objects. These two inflections of picturesque already existed in English usage, but to make them clearer, translations of Wölfflin since 1932 have rendered the more complex use of 'malerisch' through the neologism ‘painterly’. Other historians did not accept the neologism. In particular, Nikolaus Pevsner, imbued with the German tradition, wrote in his English language texts of the 'malerisch' qualities of architecture and urbanism as ‘picturesque’. Thus, a level of confusion has resulted in distinguishing ‘painterly’ and ‘picturesque’, as if there was a conceptual difference marked in everyday language, rather than a difference constructed by the institutions of art history. Translations, and particularly those that make common words into defined terms, are valuable points of historical enquiry in their own right. At such points we can recover some of the complexity and historical density that has been lost in the schematisation that has come about through translation.

We report on GaN lasers with extremely narrow linewidth (

Multiple laser-diode topologies designed for compact, stable, narrow-linewidth sources ranging from the blue (420 nm) to the red (780 nm) for use in quantum technology applications where absolute frequency accuracy and stability is key.