451 research outputs found
Technology for Submillimeter Astronomy
Despite about three decades of progress, the field of submillimeter astronomy remains quite challenging, because the detection technology is still under development and the transmission of the atmosphere is poor. The latter problem has been overcome by constructing submillimeter telescopes at excellent sites, first on Mauna Kea and later in Chile and Antarctica, and also by using airborne and space telescopes. Meanwhile, the improvements in technology over the past several decades have been remarkable. While considerable opportunities for improvement remain, existing detector and receiver technologies now often approach fundamental limits. This technological revolution has brought submillimeter astronomy from the fringes to the forefront of modern astrophysics and has stimulated major investments such as the 50-element ALMA interferometer and the ESA/NASA Herschel Space Observatory
Monolayer graphene bolometer as a sensitive far-IR detector
In this paper we give a detailed analysis of the expected sensitivity and
operating conditions in the power detection mode of a hot-electron bolometer
(HEB) made from a few {\mu}m of monolayer graphene (MLG) flake which can be
embedded into either a planar antenna or waveguide circuit via NbN (or NbTiN)
superconducting contacts with critical temperature ~ 14 K. Recent data on the
strength of the electron-phonon coupling are used in the present analysis and
the contribution of the readout noise to the Noise Equivalent Power (NEP) is
explicitly computed. The readout scheme utilizes Johnson Noise Thermometry
(JNT) allowing for Frequency-Domain Multiplexing (FDM) using narrowband filter
coupling of the HEBs. In general, the filter bandwidth and the summing
amplifier noise have a significant effect on the overall system sensitivity.
The analysis shows that the readout contribution can be reduced to that of the
bolometer phonon noise if the detector device is operated at 0.05 K and the JNT
signal is read at about 10 GHz where the Johnson noise emitted in equilibrium
is substantially reduced. Beside the high sensitivity (NEP < 10
W/Hz, this bolometer does not have any hard saturation limit and thus
can be used for far-IR sky imaging with arbitrary contrast. By changing the
operating temperature of the bolometer the sensitivity can be fine tuned to
accommodate the background photon flux in a particular application. By using a
broadband low-noise kinetic inductance parametric amplifier, ~100s of graphene
HEBs can be read simultaneously without saturation of the system output.Comment: 9 pages. 6 figure, SPIE Astronomical Telescopes + Instrumentation,
Montr\'eal, Quebec, Canada, 22-27 June, 201
A Frequency Selective Surface based focal plane receiver for the OLIMPO balloon-borne telescope
We describe here a focal plane array of Cold-Electron Bolometer (CEB)
detectors integrated in a Frequency Selective Surface (FSS) for the 350 GHz
detection band of the OLIMPO balloon-borne telescope. In our architecture, the
two terminal CEB has been integrated in the periodic unit cell of the FSS
structure and is impedance matched to the embedding impedance seen by it and
provides a resonant interaction with the incident sub-mm radiation. The
detector array has been designed to operate in background noise limited
condition for incident powers of 20 pW to 80 pW, making it possible to use the
same pixel in both photometric and spectrometric configurations. We present
high frequency and dc simulations of our system, together with fabrication
details. The frequency response of the FSS array, optical response measurements
with hot/cold load in front of optical window and with variable temperature
black body source inside cryostat are presented. A comparison of the optical
response to the CEB model and estimations of Noise Equivalent power (NEP) is
also presented
Bolometric response in graphene based superconducting tunnel junctions
We fabricate graphene-TiOx-Al tunnel junctions and characterize their radio
frequency response. Below the superconducting critical temperature of Al and
when biased within the superconducting gap, the devices show enhanced dynamic
resistance which increases with decreasing temperature. Application of radio
frequency radiation affects the dynamic resistance through electronic heating.
The relation between the electron temperature rise and the absorbed radiation
power is measured, from which the bolometric parameters, including heat
conductance, noise equivalent power and responsivity, are characterized
Bolometers
Infrared Detectors and technologies are very important for a wide range of applications, not only for Military but also for various civilian applications. Comparatively fast bolometers can provide large quantities of low cost devices opening up a new era in infrared technologies. This book deals with various aspects of bolometer developments. It covers bolometer material aspects, different types of bolometers, performance limitations, applications and future trends. The chapters in this book will be useful for senior researchers as well as beginning graduate students
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
Ultra-fast direct detectors for the THz frequency range
For the analysis and optimization of the picosecond pulsed terahertz radiation generated by electron storage rings or other pulsed sources, ultra-fast detectors are required which are able to resolve picosecond dynamic processes directly in the time domain. In this book, a new direct terahertz detector technology based on the high-temperature superconductor YBa2Cu3O7-x has been developed which opens new routes in the analysis of picosecond time-domain processes with a wide dynamic range
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