We have done the following during the project
- developing the laboratory infrastructure and techniques to allow efficient testing of our spectrometer chips and the procurement of the cryogenic system for the final instrument. (See Haenle et al., 2018 and Davis et al., (2018))
- several radiation coupling schemes and their coupling efficiency. We have studied, designed, tested and verified the performance of narrow-band twin-slot antenna’s (Ferrari et al, 2018) and broad band antenna’s, both single polarization (See Bueno et al., 2017 and Bueno et al., 2018) and dual polarization (see Yurduseven et al., 2018). The broad band leaky wave antenna will be the antenna of choice for the broad band prototype currently under development. The twin-slot antenna was used in the first demonstration of the proposed on-chip filterbank technology.
- we have studied how to control surface waves, or stray radiation, coupled to the chip itself (see Yates et al., 2017 and Yates et al., 2018). This is crucial, since this ‘stray-light’ can coupled directly to the detectors, forming a by-pass of the spectrometer. A novel method using Beta-phase Ta mesh absorbers was implemented and tested in large imaging arrays.
- we have done a full imaging array system test, to do an end-to-end demonstration of a large-scale detector system, including readout, that reaches the performance needed for the detector arrays in our specrometers (see Baselmans et al, 2017)
- we have demonstrated both in the laboratory as well as on the ASTE 10 m telescope in Chile a full spectrometer system operating in the 330-380 GHz frequency band with a resolution of 300. I attach an image with a drawing of the chip and a picture of the real chip in my hand. The chip has an antenna that couples the radiation from the telescope to a transmission line, which sends the signal to a set of filters. Behind each filter is an MKID detector, each sensing the power in a small frequency band. The other image shows the ASTE telescope where the first-light camapign was done, together with an image of the system cryostat mounted in the telescope cabin. This is the first ever demonstration of the on-chip filterbank technology, and the most broad-band spectrometer ever constructed for far infrared astronomy. We have spectroscopically resolved several galactic and extra galactic sources proving that the technology for MOSAIC does work in a real system. This work is published in En do et al., Nature Astronomy volume 3, pages989–996(2019)
DOI: 10.1038/s41550-019-0850-8
- We found that planar filter technology as used in the ASTE campaign has a fundamental flaw that limits the performance. We wnet back to a technology based upon so-called microstriplines, where 2 superconducting metals are stacked on top of each other with a layer of isolating material in between. It is this isolator that creates typically too much losses. We found that amorphous Si deposited using chemical vapour deposition is vastly superior over other technologies by doing a dedicated measurement using a completely new measurement technique as described by S. Haehnle et al.,Applied Physics Letters 182601, (2020) for planar structures. Simuilar measurements as in this paper show a god enough performance of the Si based striplines, a paper is submitted to Physical review Applied by the same author.
- Using this new stripline technology we ave designed and tested a new type of filter that fulfils all requirements for future on-chip spectrometers. A paper is submitted by A. Laguna to the IEEE THz transactions. With this result we have started fabricating a final chip with a 220-400 GHz input bandwidth for deployment on ASTE in the summer of 2021.
- We have spend significant effort in instrument modelling, in preparation for the next telescope campaign, see E. Huijten et al, SPIE (2020).
