We present measurements of a polarization sensitive lens-antenna coupled MKID array at 1.5THz, mounted with an additional 20dB neutral density filter in a wide field camera. This allows full end to end system characterization with room temperature optical sources, but under similar optical loading conditions as expected in a space based polarimeter configuration.
The system is characterized using a wideband polarized photomixer based phase and amplitude beam pattern setup at 1.5THz. Two separate measurements with orthogonal source polarizations enable the co and cross polarization to be extracted, showing the full system low cross-polarization needed for many future polarimetric applications. Such a measurement setup is additionally of potential interest for the characterization of future missions (for example in the Far Infra-Red): to obtain the optical beam quality and verifying the optical interfaces on a component/sub-component level. We present and discuss this setup and the characterization of the lens-antenna coupled MKID camera.
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 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.
Superconducting resonators and transmission lines are fundamental building blocks of integrated circuits for millimeter-submillimeter (mm-submm) astronomy. Accurate simulation of radiation loss from the circuit is crucial for the design of these circuits because radiation loss increases with frequency, and can thereby deteriorate the system performance. Here, we show a stratification for a 2.5-dimensional method-of-moment simulator Sonnet em that enables accurate simulations of the radiative resonant behavior of submm-wave coplanar resonators and straight coplanar waveguides. The Sonnet simulation agrees well with the measurement of the transmission through a coplanar resonant filter at 374.6 GHz. Our Sonnet stratification utilizes artificial lossy layers below the lossless substrate to absorb the radiation, and we use co-calibrated internal ports for de-embedding. With this type of stratification, Sonnet can be used to model superconducting mm-submm wave circuits even when radiation loss is a potential concern.
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 next technological breakthrough in millimeter–submillimeter astronomy is three-dimensional imaging spectrometry with wide instantaneous spectral bandwidths and wide fields of view. The total optimization of the focal-plane instrument, the telescope, the observing strategy, and the signal-processing software must enable efficient removal of foreground emission from the Earth’s atmosphere, which is time-dependent and highly nonlinear in frequency. Here, we present Time-dependent End-to-end Model for Post-process Optimization (TiEMPO) of the DEep Spectroscopic HIgh-redshift MApper (DESHIMA) spectrometer. TiEMPO utilizes a dynamical model of the atmosphere and parameterized models of the astronomical source, the telescope, the instrument, and the detector. The output of TiEMPO is a time stream of sky brightness temperature and detected power, which can be analyzed by standard signal-processing software. We first compare TiEMPO simulations with an on-sky measurement by the wideband DESHIMA spectrometer, and find good agreement in the noise and sensitivity. We then use TiEMPO to simulate the detection of the line emission spectrum of a high-redshift galaxy using the DESHIMA 2.0 spectrometer in development. The TiEMPO model is open source. Its modular and parametrized design enables users to adapt it to optimize the end-to-end performance of spectroscopic and photometric instruments on existing and future telescopes.
Microfabrication of on-chip filterbanks, such as DESHIMA 2.0, would greatly benefit from reliable fabrication with sub-micrometer resolution. This enables smaller devices and reduces scatter in parameters such as filter bandwidth and resonant frequency. Here we present “mix-and-match” processing by combining optical and electron-beam exposures of a single layer of negative ma-N1405 resist from Micro-Resist-Technology GmbH. This allows for minimal features down to 300 nm where needed and large structure exposure with UV, limiting e-beam writing time. Relative alignment is possible to less than 500 nm on a regular basis.
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.
Superconducting resonators and transmission lines are fundamental building blocks of integrated circuits for millimeter-submillimeter astronomy. Accurate simulation of radiation loss from the circuit is crucial for the design of these circuits because radiation loss increases with frequency, and can thereby deteriorate the system performance. Here we show a stratification for a 2.5-dimensional method-of-moment simulator Sonnet EM that enables accurate simulations of the radiative resonant behavior of submillimeter-wave coplanar resonators and straight coplanar waveguides (CPWs). The Sonnet simulation agrees well with the measurement of the transmission through a coplanar resonant filter at 374.6 GHz. Our Sonnet stratification utilizes artificial lossy layers below the lossless substrate to absorb the radiation, and we use co-calibrated internal ports for de-embedding. With this type of stratification, Sonnet can be used to model superconducting millimeter-submillimeter wave circuits even when radiation loss is a potential concern.
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 next technological breakthrough in millimeter-submillimeter astronomy is 3D imaging spectrometry with wide instantaneous spectral bandwidths and wide fields of view. The total optimization of the focal-plane instrument, the telescope, the observing strategy, and the signal-processing software must enable efficient removal of foreground emission from the Earth's atmosphere, which is time-dependent and highly nonlinear in frequency. Here we present TiEMPO : Time-dependent End-to-end Model for Post-process Optimization of the DESHIMA spectrometer. TiEMPO utilizes a dynamical model of the atmosphere and parametrized models of the astronomical source, the telescope, the instrument, and the detector. The output of TiEMPO is a timestream of sky brightness temperature and detected power, which can be analyzed by standard signal-processing software. We first compare TiEMPO simulations with an on-sky measurement by the wideband DESHIMA spectrometer, and find good agreement in the noise power spectral density and sensitivity. We then use TiEMPO to simulate the detection of the line emission spectrum of a high-redshift galaxy using the DESHIMA 2.0 spectrometer in development. The TiEMPO model is open source. Its modular and parametrized design enables users to adapt it to design and optimize the end-to-end performance of spectroscopic and photometric instruments on existing and future telescopes.
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.
Terahertz spectrometers with a wide instantaneous frequency coverage for passive remote sensing are enormously attractive for many terahertz applications, such as astronomy, atmospheric science, and security. Here we demonstrate a wide-band terahertz spectrometer based on a single superconducting chip. The chip consists of an antenna coupled to a transmission line filterbank, with a microwave kinetic inductance detector behind each filter. Using frequency division multiplexing, all detectors are read-out simultaneously, creating a wide-band spectrometer with an instantaneous bandwidth of 45 GHz centered around 350 GHz. The spectrometer has a spectral resolution of F / ΔF = 380 and reaches photon-noise limited sensitivity. We discuss the chip design and fabrication, as well as the system integration and testing. We confirm full system operation by the detection of an emission line spectrum of methanol gas. The proposed concept allows for spectroscopic radiation detection over large bandwidths and resolutions up to F / ΔF ∼ 1000, all using a chip area of a few cm2. This will allow the construction of medium resolution imaging spectrometers with unprecedented speed and sensitivity.
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