318 research outputs found
Nanobolometers for THz Photon Detection
This article reviews the state of rapidly emerging terahertz hot-electron
nanobolometers (nano-HEB), which are currently among of the most sensitive
radiation power detectors at submillimeter wavelengths. With the achieved noise
equivalent power close to 10^{-19} W/Hz^{1/2} and potentially capable of
approaching NEP ~ 10^{-20} W/Hz^{1/2}, nano-HEBs are very important for future
space astrophysics platforms with ultralow submillimeter radiation background.
The ability of these sensors to detect single low-energy photons opens
interesting possibilities for quantum calorimetry in the mid-infrared and even
in the farinfrared parts of the electromagnetic spectrum. We discuss the
competition in the field of ultrasensitive detectors, the physics and
technology of nano-HEBs, recent experimental results, and perspectives for
future development.Comment: 16 pages, 12 figures, 128 reference
Energy resolution of terahertz single-photon-sensitive bolometric detectors
We report measurements of the energy resolution of ultra-sensitive
superconducting bolometric detectors. The device is a superconducting titanium
nanobridge with niobium contacts. A fast microwave pulse is used to simulate a
single higher-frequency photon, where the absorbed energy of the pulse is equal
to the photon energy. This technique allows precise calibration of the input
coupling and avoids problems with unwanted background photons. Present devices
have an intrinsic full-width at half-maximum energy resolution of approximately
23 terahertz, near the predicted value due to intrinsic thermal fluctuation
noise.Comment: 11 pages (double-spaced), 5 figures; minor revision
Ultra-Sensitive Hot-Electron Nanobolometers for Terahertz Astrophysics
The background-limited spectral imaging of the early Universe requires
spaceborne terahertz (THz) detectors with the sensitivity 2-3 orders of
magnitude better than that of the state-of-the-art bolometers. To realize this
sensitivity without sacrificing operating speed, novel detector designs should
combine an ultrasmall heat capacity of a sensor with its unique thermal
isolation. Quantum effects in thermal transport at nanoscale put strong
limitations on the further improvement of traditional membrane-supported
bolometers. Here we demonstrate an innovative approach by developing
superconducting hot-electron nanobolometers in which the electrons are cooled
only due to a weak electron-phonon interaction. At T<0.1K, the electron-phonon
thermal conductance in these nanodevices becomes less than one percent of the
quantum of thermal conductance. The hot-electron nanobolometers, sufficiently
sensitive for registering single THz photons, are very promising for
submillimeter astronomy and other applications based on quantum calorimetry and
photon counting.Comment: 19 pages, 3 color figure
Tools for the development of learning objects in artistic education
При финансовой поддержке Российского гуманитарного научного фонда, проект № 07-06-14162
Wave Function of a Brane-like Universe
Within the mini-superspace model, brane-like cosmology means performing the
variation with respect to the embedding (Minkowski) time before fixing
the cosmic (Einstein) time . The departure from Einstein limit is
parameterized by the 'energy' conjugate to , and characterized by a
classically disconnected Embryonic epoch. In contrast with canonical quantum
gravity, the wave-function of the brane-like Universe is (i) -dependent,
and (ii) vanishes at the Big Bang. Hartle-Hawking and Linde proposals dictate
discrete 'energy' levels, whereas Vilenkin proposal resembles -particle
disintegration.Comment: Revtex, 4 twocolumn pages, 3 eps figures (accepted for publication in
Class. Quan. Grav.
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