3,319 research outputs found
The case for joined-up research on carbon emissions from the building stock: adding value to household and building energy datasets
To reach UK objectives for reducing carbon emissions, it is argued that joined-up research on energy use in buildings is essential to develop and support government policy initiatives. The performance based approach introduced in Part-L of the 2006 Building Regulations has further underlined the role of coordinated research to monitor their effectiveness and provide feedback for subsequent revisions. Unfortunately, differences in dwelling classifications systems used in major household surveys currently hinder much of the supporting analysis that might improve SAP and other energy models. The Carbon Reduction in Buildings project has begun a process of integrating or organising existing building energy datasets into a coherent structure for the domestic sector. In addition, it is proposed to archive these for researchers via a building data repository that would facilitate joined-up research more widely
Receipt from T. Firth to Estate of Robert Goelet, page 1/2, duplicate
https://digitalcommons.salve.edu/goelet-new-york/1330/thumbnail.jp
Receipt from T. Firth
https://digitalcommons.salve.edu/goelet-new-york/1336/thumbnail.jp
Receipt from T. Firth, duplicate
https://digitalcommons.salve.edu/goelet-new-york/1334/thumbnail.jp
Self-pulsing dynamics in a cavity soliton laser
The dynamics of a broad-area vertical-cavity surface-emitting laser (VCSEL) with frequency-selective feedback supporting bistable spatial solitons is analyzed experimentally and theoretically. The transient dynamics of a switch-on of a soliton induced by an external optical pulse shows strong self-pulsing at the external-cavity round-trip time with at least ten modes excited. The numerical analysis indicates an even broader bandwidth and a transient sweep of the center frequency. It is argued that mode-locking of spatial solitons is an interesting and viable way to achieve three-dimensional, spatio-temporal self-localization and that the transients observed are preliminary indications of a transient cavity light bullet in the dynamics, though on a non negligible background
Frequency and phase locking of laser cavity solitons
Self-localized states or dissipative solitons have the freedom of translation in systems with a homogeneous background. When compared to cavity solitons in coherently driven nonlinear optical systems, laser cavity solitons have the additional freedom of the optical phase. We explore the consequences of this additional Goldstone mode and analyse experimentally and numerically frequency and phase locking of laser cavity solitons in a vertical-cavity surface-emitting laser with frequency-selective feedback. Due to growth-related variations of the cavity resonance, the translational symmetry is usually broken in real devices. Pinning to different defects means that separate laser cavity solitons have different frequencies and are mutually incoherent. If two solitons are close to each other, however, their interaction leads to synchronization due to phase and frequency locking with strong similarities to the Adler-scenario of coupled oscillators
Effects of a localized beam on the dynamics of excitable cavity solitons
We study the dynamical behavior of dissipative solitons in an optical cavity
filled with a Kerr medium when a localized beam is applied on top of the
homogeneous pumping. In particular, we report on the excitability regime that
cavity solitons exhibits which is emergent property since the system is not
locally excitable. The resulting scenario differs in an important way from the
case of a purely homogeneous pump and now two different excitable regimes, both
Class I, are shown. The whole scenario is presented and discussed, showing that
it is organized by three codimension-2 points. Moreover, the localized beam can
be used to control important features, such as the excitable threshold,
improving the possibilities for the experimental observation of this
phenomenon.Comment: 9 Pages, 12 figure
Optical pattern formation with a 2-level nonlinearity
We present an experimental and theoretical investigation of spontaneous
pattern formation in the transverse section of a single retro-reflected laser
beam passing through a cloud of cold Rubidium atoms. In contrast to previously
investigated systems, the nonlinearity at work here is that of a 2-level atom,
which realizes the paradigmatic situation considered in many theoretical
studies of optical pattern formation. In particular, we are able to observe the
disappearance of the patterns at high intensity due to the intrinsic saturable
character of 2-level atomic transitions.Comment: 5 pages, 4 figure
Large optical gain from four-wave mixing instabilities in semiconductor quantum wells
Based on a microscopic many-particle theory, we predict large optical gain in
the probe and background-free four-wave mixing directions caused by excitonic
instabilities in semiconductor quantum wells. For a single quantum well with
radiative-decay limited dephasing in a typical pump-probe setup we discuss the
microscopic driving mechanisms and polarization and frequency dependence of
these instabilities
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