Report

Teaser, summary, work performed and final results

Periodic Reporting for period 2 - MOSAIC (Multi object spectrometer with an array of superconducting integrated circuits)

Teaser

Recent sub-millimeter instruments on the Herschel Space Observatory, operational from 2009-2013, have discovered thousands of sub-millimeter galaxies, whose combined emission forms the cosmic infrared background. A major challenge is to measure their distance, or age, by...

Summary

Recent sub-millimeter instruments on the Herschel Space Observatory, operational from 2009-2013, have discovered thousands of sub-millimeter galaxies, whose combined emission forms the cosmic infrared background. A major challenge is to measure their distance, or age, by determining their redshifts, which also has to be based on the sub-millimeter wave signals (because they do not have an optical counterpart). In this project I propose to develop a new redshift survey instrument, using recent progress in superconducting nanotechnology, which can spectrally resolve a large fraction of the cosmic infrared background from the ground. This will allow for a very significant increase in our understanding of the formations of stars and galaxies and the evolution of the universe as a whole.
The instrument will be a Multi-Object Spectrometer with an Array of superconducting Integrated Circuits. It consists of a 3D integrated field spectrograph with a 2D array of spatial pixels sparsely filling the re-imaged focal plane of the observatory. Each pixel consists of a small lens that couples radiation from the telescope into a small (about 2x5 cm) integrated circuit that is fabricated using standard lithographic techniques. It is the development of his chip that is the main challenge of this project. It is based upon a superconducting thin film, which allows analogue signal processing of the signals without any losses. The chip has a small antenna to couple radiation from the lens into a transmission line that transports the signal to an on-chip spectrometer that filters the radiation into narrow frequency channels. Each frequency bin is coupled to an individual detector, which is read-out using dedicated hardware. The system can spectroscopically measure radiation at frequencies in between 80 GHz and 1 THz due to the materials used and will be operated at 0.1K (-273 degree C) inside a dedicated cryostat.

Work performed

I have focussed in the first 18 months of the project on:
- 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 camapugn 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. We are preparing 2 manuscripts.

Final results

- We have demonstrated the most sensitive imaging system for far-infrared astronomy in the laboratory (Baselmans et al., 2017)
- We have demonstrated the first on-chip filterbank (Endo et al., in preparation)
- We have demonstrated the first octave-band radiation detection scheme using super-THz antenna’s (Bueno et al., 2017)
- We have demonstrated the first ever true dual polarization detector operating over an octave of bandwidth (Yurduseven et al., 2018).