50 research outputs found
Surface wave control for large arrays of microwave kinetic inductance detectors
Large ultra-sensitive detector arrays are needed for present and future
observatories for far infra-red, submillimeter wave (THz), and millimeter wave
astronomy. With increasing array size, it is increasingly important to control
stray radiation inside the detector chips themselves, the surface wave. We
demonstrate this effect with focal plane arrays of 880 lens-antenna coupled
Microwave Kinetic Inductance Detectors (MKIDs). Presented here are near field
measurements of the MKID optical response versus the position on the array of a
reimaged optical source. We demonstrate that the optical response of a detector
in these arrays saturates off-pixel at the dB level compared to the
peak pixel response. The result is that the power detected from a point source
at the pixel position is almost identical to the stray response integrated over
the chip area. With such a contribution, it would be impossible to measure
extended sources, while the point source sensitivity is degraded due to an
increase of the stray loading. However, we show that by incorporating an
on-chip stray light absorber, the surface wave contribution is reduced by a
factor 10. With the on-chip stray light absorber the point source response
is close to simulations down to the dB level, the simulation based on
an ideal Gaussian illumination of the optics. In addition, as a crosscheck we
show that the extended source response of a single pixel in the array with the
absorbing grid is in agreement with the integral of the point source
measurements.Comment: accepted for publication in IEEE Transactions on Terahertz Science
and Technolog
Eliminating stray radiation inside large area imaging arrays
With increasing array size, it is increasingly important to control stray
radiation inside the detector chips themselves. We demonstrate this effect with
focal plane arrays of absorber coupled Lumped Element microwave Kinetic
Inductance Detectors (LEKIDs) and lens-antenna coupled distributed quarter
wavelength Microwave Kinetic Inductance Detectors (MKIDs). In these arrays the
response from a point source at the pixel position is at a similar level to the
stray response integrated over the entire chip area. For the antenna coupled
arrays, we show that this effect can be suppressed by incorporating an on-chip
stray light absorber. A similar method should be possible with the LEKID array,
especially when they are lens coupled.Comment: arXiv admin note: substantial text overlap with arXiv:1707.0214
Proof-of-Concept Demonstration of Vector Beam Pattern Measurements of Kinetic Inductance Detectors
We present results from the first vector beam pattern measurement ofmicrowave kinetic inductance detectors (MKIDs). Vector beam patterns require sampling of the E-field of the receiver in both amplitude and phase. MKIDs are inherently direct detectors and have no phase response to incoming radiation. We map the amplitude and phase patterns of the detector beam profile by adapting a two-source heterodyne technique. Our testing strategy recovers the phase information by creating a reference signal to trigger data acquisition. The reference is generated by mixing the slightly offset low-frequency signals from the output of the two synthesizers used to drive the submillimeter sources. The key requirement is that the time-series record always begins at the same set phase of the reference signal. As the source probe is scanned within the receiver beam, the wavefront propagation phase of the receiver changes and causes a phase offset between the detector output and reference signals. We demonstrated this technique on the central pixel of a test array operating at 350 GHz. This methodology will enable vector beam pattern measurements to be performed on direct detectors, which have distinct advantages reducing systematic sources of error, allowing beam propagation, and removing the far-field measurement requirement such that complicated optical systems can be measured at a point that is easily accessible, including the near field
An Ultra-Wideband Leaky Lens Antenna for Broadband Spectroscopic Imaging Applications
We present the design, fabrication and characterisation of a broadband leaky
lens antenna for broadband, spectroscopic imaging applications. The antenna is
designed for operation in the 300-900 GHz band. We integrate the antenna
directly into an Al-NbTiN hybrid MKID to measure the beam pattern and absolute
coupling efficiency at three frequency bands centred around 350, 650 and 850
GHz, covering the full antenna band. We find an aperture efficiency over the whole frequency band, limited by lens reflections. We
find a good match with simulations for both the patterns and efficiency,
demonstrating a 1:3 bandwidth in the sub-mm wavelength range for future on-chip
spectrometers.Comment: Accepted for Publication at IEEE Transactions on Antennas and
Propagatio
Resolving Power of Visible to Near-Infrared Hybrid -Ta/NbTiN Kinetic Inductance Detectors
Kinetic Inductance Detectors (KIDs) are superconducting energy-resolving
detectors, sensitive to single photons from the near-infrared to ultraviolet.
We study a hybrid KID design consisting of a beta phase tantalum (-Ta)
inductor and a NbTiN interdigitated capacitor (IDC). The devices show an
average intrinsic quality factor of 4.3 1.3
. To increase the power captured by the light sensitive inductor,
we 3D-print an array of 150150 m resin micro lenses on the
backside of the sapphire substrate. The shape deviation between design and
printed lenses is smaller than 1m, and the alignment accuracy of this
process is m and
m. We measure a resolving power for 1545-402 nm that is limited to 4.9 by
saturation in the KID's phase response. We can model the saturation in the
phase response with the evolution of the number of quasiparticles generated by
a photon event. An alternative coordinate system that has a linear response
raises the resolving power to 5.9 at 402 nm. We verify the measured resolving
power with a two-line measurement using a laser source and a monochromator. We
discuss several improvements that can be made to the devices on a route towards
KID arrays with high resolving powers.Comment: 11 pages, 9 Figues, Journal Pape
Factors associated with pastoral community knowledge and occurrence of mycobacterial infections in human-animal interface areas of Nakasongola and Mubende districts, Uganda
<p>Abstract</p> <p>Background</p> <p>Nontuberculous mycobacteria (NTM) are emerging opportunistic pathogens whose role in human and animal disease is increasingly being recognized. Major concerns are their role as opportunistic pathogens in HIV/AIDS infections. The role of open natural water sources as source and livestock/wildlife as reservoirs of infections to man are well documented. This presents a health challenge to the pastoral systems in Africa that rely mostly on open natural water sources to meet livestock and human needs. Recent study in the pastoral areas of Uganda showed infections with same genotypes of NTM in pastoralists and their livestock. The aim of this study was to determine the environmental, animal husbandry and socio-demographic factors associated with occurrence and the pastoral community knowledge of mycobacterial infections at the human-environment-livestock/wildlife interface (HELI) areas in pastoral ecosystems of Uganda.</p> <p>Methods</p> <p>Two hundred and fifty three (253) individuals were subjected to a questionnaire survey across the study districts of Nakasongola and Mubende. Data were analyzed using descriptive statistics and multivariable logistic regression analysis.</p> <p>Results</p> <p>Humans sharing of the water sources with wild animals from the forest compared to savannah ecosystem (OR = 3.3), the tribe of herding pastoral community (OR = 7.9), number of rooms present in household (3-5 vs. 1-2 rooms) (OR = 3.3) were the socio-demographic factors that influenced the level of knowledge on mycobacterial infections among the pastoral communities. Tribe (OR = 6.4), use of spring vs. stream water for domestic use (OR = 4.5), presence of sediments in household water receptacle (OR = 2.32), non separation of water containers for drinking and domestic use (OR = 2.46), sharing of drinking water sources with wild animals (OR = 2.1), duration of involvement of >5 yrs in cattle keeping (OR = 3.7) and distance of household to animal night shelters (>20 meters) (OR = 3.8) were significant socio-demographic factors associated with the risk of occurrence of mycobacterioses among the pastoral communities in Uganda.</p> <p>Conclusion</p> <p>The socio-demographic, environmental and household related factors influence the risk of occurrence as well as pastoralists' knowledge of mycobacterial infections in the pastoral households at the human-environment-livestock/wildlife pastoral interface areas of Uganda.</p
First light demonstration of the integrated superconducting spectrometer
Ultra-wideband 3D imaging spectrometry in the millimeter-submillimeter
(mm-submm) band is an essential tool for uncovering the dust-enshrouded portion
of the cosmic history of star formation and galaxy evolution. However, it is
challenging to scale up conventional coherent heterodyne receivers or
free-space diffraction techniques to sufficient bandwidths (1 octave) and
numbers of spatial pixels (>). Here we present the design and first
astronomical spectra of an intrinsically scalable, integrated superconducting
spectrometer, which covers 332-377 GHz with a spectral resolution of . It combines the multiplexing advantage of microwave kinetic
inductance detectors (MKIDs) with planar superconducting filters for dispersing
the signal in a single, small superconducting integrated circuit. We
demonstrate the two key applications for an instrument of this type: as an
efficient redshift machine, and as a fast multi-line spectral mapper of
extended areas. The line detection sensitivity is in excellent agreement with
the instrument design and laboratory performance, reaching the atmospheric
foreground photon noise limit on sky. The design can be scaled to bandwidths in
excess of an octave, spectral resolution up to a few thousand and frequencies
up to 1.1 THz. The miniature chip footprint of a few
allows for compact multi-pixel spectral imagers, which would enable
spectroscopic direct imaging and large volume spectroscopic surveys that are
several orders of magnitude faster than what is currently possible.Comment: Published in Nature Astronomy. SharedIt Link to the full published
paper: https://rdcu.be/bM2F
Epitaxial Growth and Processing of Compound Semiconductors
Contains an introduction and reports on three research projects.MIT Lincoln LaboratoryU.S. Air Force - Office of Scientific Research Grant F49620-96-1-0126National Science Foundation Grant DMR 94-00334Joint Services Electronics Progra