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.
We present transmission and loss measurements of 3D printed alumina and reflectance measurement of a sample with 3D printed sub-wavelength structures anti-reflection coatings (SWS-ARC). For a band between 160 and 700 GHz we find an index of refraction n = 3.11 ± 0.01 and loss tan δ = 0.002 ± 0.003. Transmission measurements between 160 and 250 GHz of a sample with SWS-ARC 3D printed on one side give a reduction of reflectance from a maximum of 64% to a maximum of 31% over the band, closely matching predictions. These first measurements of the index and loss over this frequency band suggest that the material could be useful for astrophysical applications.
We present designs and fabrications of sub-wavelength anti-reflection structures on alumina for infrared filters at three observational frequency bands near 30, 125, and 250 GHz, which are widely used for instruments measuring cosmic microwave background (CMB) radiation from the ground. The three observational windows contain the two observational bands in each receiver, and the corresponding fractional bandwidth is about 60%. We used laser ablation to directly machine on alumina substrate. This technology is robust against the use of an optical element at the cryogenic temperature with which all the CMB telescope receivers have to comply. Based on the fabricated 9 (3 × 3) pyramidal structures, we computed the expected averaged transmittance of above 0.97 for each of the three filter designs including anticipated absorptive loss, the loss tangent of 4 × 10−4, and the incident angle up to 20 degrees. The band averaged instrumental polarization, the fractional difference between the p and s-state incident polarization states, is computed and they are less than ±4 × 10−3 for the bands and incident angles.
We used laser ablation to fabricate sub-wavelength structure anti-reflection coating (SWS-ARC) on a 5 cm diameter alumina lens. With an aspect ratio of 2.5, the SWS-ARC are designed to give a broad-band low reflectance response between 110 and 290 GHz. SWS shape measurements give 303 μm pitch and total height between 750 and 790 μm height, matching or exceeding the aspect ratio design values. Millimeter-wave transmittance measurements in a band between 140 and 260 GHz show the increase in transmittance expected with the ARC when compared to finite element analysis electromagnetic simulations. To our knowledge, this is the first demonstration of SWS-ARC on an alumina lens, opening the path for implementing the technique for larger diameter lenses.
Federico Cacciotti, Alessandro Paiella, Camille Avestruz, Ritoban Basu Thakur, Elia Battistelli, Paolo de Bernardis, Esra Bulbul, Fabio Columbro, Alessandro Coppolecchia, Scott Cray, Giuseppe D'Alessandro, Marco De Petris, Shaul Hanany, Luca Lamagna, Erwin Lau, Silvia Masi, Giorgio Pettinari, Francesco Piacentini, Jack Sayers, Irina Zhuravleva
OLIMPO is a 2.6m balloon–borne telescope intended to observe, with high–angular resolution, the millimeter and sub–millimeter sky from the Antarctic stratosphere. It will allow us to study the dynamics of galaxy cluster formation and to characterize the intergalactic medium up to the cluster outskirt through the Sunyaev-Zel’dovich effect. OLIMPO utilizes four arrays of kinetic inductance detectors (KIDs), in the 145, 250, 350 and 460 GHz bands, operated at about 300 mK. OLIMPO has already flown, in a technological flight, in 2018 from Svalbard, Norway, proving for the first time that KIDs are capable to withstand the demanding conditions on high altitude balloons. KIDs are superconducting, low–temperature detectors suited for this kind of applications due to their intrinsic capability to be frequency–domain multiplexed, enabling very high–sensitivity sky surveys. In this work, we present the design, optimization and laboratory characterization of the 313–pixel array for the OLIMPO 350 GHz frequency band. We showcase results of the electrical characterization (electrical responsivity and the measurement of the quasiparticle lifetime) and the optical characterization (optical responsivity and optical efficiency) accomplished with a 4K cooled black body.
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