We present a plan for sub/millimeter-wave line intensity mapping (LIM) using an imaging spectrograph based on the Terahertz Integral Field Units with Universal Nanotechnology (TIFUUN) architecture. We aim to measure the dust-enshrouded cosmic star formation rate density within the first 2 billion years by conducting LIM observations of ionized carbon [C II] 158 μm and oxygen [O III] 88 μm lines, redshifted to sub/millimeter wavelengths. The proposed imaging spectrograph will simultaneously observe two frequency bands: Band-1 (139-179 GHz) and Band-2 (248-301 GHz). Each band will feature up to ∼100 imaging pixels (spaxels), with each spaxel having 100 spectral channels, providing a modest spectral resolution (R~500). The total number of detectors (voxels) will reach ~20,000. This dual-band configuration will allow simultaneous measurement of key spectral lines, e.g., [C II] 158 μm and [O III] 88 μm lines at z = 10.2 - 12.6, and CO(4-3), (7-6), [C I](1-0) and (2-1) at z = 1.9 - 2.2, enabling cross-correlation analysis. We will develop data-scientific methods to remove atmospheric noise using sparse modeling and to extract signals from the observed data using deep learning.
We present the design and cryogenic characterization of highly sensitive 7 THz lens-antenna-coupled MKIDs for future actively cooled far-infrared space telescopes. This is the highest operating frequency ever demonstrated for antenna-coupled MKIDs. The detector is based on a broadband leaky-wave lens-antenna coupled to a hybrid (Al/NbTiN) CPW MKID. Both the antenna and the photosensitive Al section of the MKID lay on a thin dielectric membrane, improving both the antenna efficiency and the detector sensitivity. The high operating frequency requires the definition of sub-micron features with electron-beam lithography, pristine laser-ablated lenses, and very accurate alignments during assembly. We have tested a prototype chip and have obtained a detector noise equivalent power of 3e-20W/sqrt(Hz) with a high coupling efficiency. Additionally, we have measured the antenna beam pattern. With these measurements we demonstrate a detector system suitable for highly-sensitive (imaging) spectrometers.
Future observatories for the far-infrared (FIR), such as envisioned in the NASA Probe announcement, will offer unprecedented sensitivity by using cryogenically cooled optics. Large arrays of lens-absorber coupled Microwave Kinetic Inductance Detectors (MKIDs) are the only candidate to fulfill the requirements for these observatories, requiring unprecedented sensitivity with a noise equivalent power below 10^(-19) W/√Hz while operating up to 12THz. The incoherent coupling mechanism of distributed absorbers leads to a robustness against misalignment, assembly, and fabrication issues at FIR wavelengths. In this contribution, we will present the design and fabrication of large arrays of lens-absorber coupled detectors and evaluate their performance at 7 and 12THz and demonstrate an NEP of 0.7⋅10^(-19) W/√Hz.
We present the on-sky commissioning and science verification of DESHIMA 2.0: the first science-grade integrated superconducting spectrometer (ISS) for ultra-wideband mm-submm spectroscopy. With an instantaneous band coverage of 205-392 GHz at a spectral resolution of F/dF = 500, DESHIMA 2.0 will be applied to emission line surveys and redshift measurement of dusty star-forming galaxies, spectroscopic Sunyaev–Zeldovich effect observations of galaxy-clusters, and other new science cases that utilize its ultra-wide bandwidth. Compared to its predecessor (DESHIMA 1.0), DESHIMA 2.0’s superconducting filterbank chip with a x4 higher optical efficiency, x4 wider instantaneous bandwidth, x20 faster position switching on the sky, and a remotely-controlled optics alignment system. DESHIMA 2.0 is currently installed on the ASTE 10-m telescope at 4860 m altitude with excellent sky transmission, and is being commissioned for science operation. In the conference we will report the on-sky performance and latest results in the science-verification campaign at ASTE.
DESHIMA 2.0 is an ultra-wideband submillimeter spectrometer based on integrated superconducting microstrip filters and Microwave Kinetic Inductance Detectors (MKIDs). We have successfully demonstrated its ultra-wideband performance in the laboratory. The measured instantaneous frequency coverage with ~300 MKIDs is 225-415 GHz, with a mean filter Q of ~670. The broadband quasi-optical chain of the instrument is characterized by beam patterns across the whole frequency range that are obtained simultaneously by a novel phase-amplitude beam measurement technique. We plan to deploy the instrument on the ASTE telescope for a commissioning and science verification campaign in 2022-2023.
The relative benefits of an offset Dragonian reflector compared to equivalent off-axis parabolic (OAP) mirrors for feeding collimated beam to a scanned beam imaging system are investigated. Physical-optics simulation of the Dragonian are performed at 500 GHz. The input is a Gaussian beam with a frequency dependent waist radius fit to the output of a standard Pickett-Potter horn. The collimated output beam properties are characterized, including cross-polarization, beam waist radius, Gaussicity, and M-squared parameter. Next, by sweeping the parameters of an OAP reflector (parent focal length and incidence angle) in the physical-optics simulations, we find the geometry in which the properties of the output beam best match the Dragonian geometry. This reflector is found to be an OAP with 108.22 mm parent focal length and 30◦ incidence angle. An additional OAP reflector is also considered in these simulations, which is the most often used 90◦ OAP. The parent focal length is 56.95 mm for this mirror, so that we have a similar beam waist radius in the detector plane. Finally, physical optics simulations reveal that the Dragonian geometry produces much smaller cross-polarization in the detector plane (−23 dB at the beam waist) in comparison with OAP reflector (being −14 dB and −8 dB for 30° and 90° off-axis mirrors, respectively). The 30° OAP reflector is able to produce similar beam quality in terms of phase variation, Gaussicity, and beam waist radius at the detector plane.
DESHIMA 2.0 will be a wideband submillimeter (submm) spectrometer based on integrated NbTiN superconducting resonant filters and Microwave Kinetic Inductance Detectors. DESHIMA 2.0 covers an instantaneous frequency band from 220 to 440 GHz with a frequency resolution of F/dF = 500 to carry out spectroscopic redshift measurements of submm-bright galaxies (SMGs). For the absolute frequency calibration of DESHIMA 2.0, we have developed a gas-cell calibration system that can be used with methanol vapor or N2O gas. The system is designed not only for the frequency calibration, but also for long integration time tests that simulate observations of faint extra-galactic lines.
DESHIMA 2.0 is a broadband sub-mm wave superconducting on-chip spectrometer for astronomy, targeting an instantaneous octave bandwidth (220 - 440 GHz) sampled with moderate spectral resolution channels (f/df ~ 500). In this work we propose a microstrip filter-bank implementation for DESHIMA 2.0 based on “H-shaped” resonators. These bandpass filters are free from spurious resonances over an octave bandwidth, do not suffer from radiation losses and can be arrayed in large filter-banks thanks to their extremely low reflections off-resonance. The design has been aided by an analytical circuit model that can fast and reliably predict the filter-bank behaviour. Prototype chips have been characterised in terms of frequency response and coupling efficiency.
DESHIMA 2.0 is a sub-millimetre wave spectrometer based on a single superconducting chip with a large instantaneous bandwidth. The instrument consists of a Quasi-optical (QO) system and an on-chip filter-bank coupled to an array of Kinetic Inductance Detectors (KID). In this work, this broad band QO system, operating at sub-millimetre wavelengths (220 GHz to 720 GHz), will be presented. This design is achieved using a field matching technique and consists of a hyper-hemispherical leaky lens antenna coupled to a series of Dragonian reflectors. The optimized design has an average illumination efficiency over the band of ~70%. This performance is also measured directly through the response of the KIDs.
The integrated superconducting spectrometer (ISS) enables ultra-wideband, large field-of-view integral-field-spectrometer designs for mm-submm wave astronomy. DESHIMA 2.0 is a single-pixel ISS spectrometer for the ASTE 10-m telescope, designed to observe the 220-440 GHz band in a single shot, corresponding to a [CII] redshift range of z=3.3-7.6. The first-light experiment of DESHIMA, using a 332-377 GHz configuration has shown excellent consistency between the performance derived from on-sky measurements, lab-measurements and the design. Ongoing upgrades towards the octave-bandwidth full system include the development of a filterbank chip with ~350 channels and higher optical efficiency, a wideband quasioptical design, and observing methods for efficiently removing the atmosphere.
Kinetic inductance bolometer (KIB) technology is a candidate for scalable submillimeter wave imaging systems, particularly suitable for person security screening applications. We have previously shown that the basic figures of merit are compatible with room-temperature radiometric imaging applications, and demonstrated the functionality of kilo-pixel detector arrays. In this article, we report on our imaging system based on 8208 KIBs organized on a 2D focal plane. We provide an overview on the basic components, including the detectors, optics, and cryogenics, and describe aspects relevant in system integration. Moreover, we demonstrate the capacity in actual concealed object detection by presenting datasets revealing metallic and dielectric objects hidden under the clothes of a test person.
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