DESHIMA (Deep Spectroscopic High-redshift Mapper)Themes: Astronomical Instrumentation
Superconducting On-chip Spectrometer for Probing the Cosmic History of Star FormationAdvanced instruments have turned cosmology into an experimental science. The emergence of sensitive submillimeter wave sensors has lead to the discovery of an unexpectedly large amount of hidden star formation in the early universe. This could force the current understanding of cosmology to be revised.
Is there more that we have been overlooking? We can answer this only by further observations with submillimeter wave cameras that have higher sensitivity and more pixels. One of the goals of such instruments is to discover many of these hidden submillimeter wave galaxies, so-called SMGs.
However, ordinary submillimeter wave cameras produce only a 2D projection of the sky (as in the spectacular image above), in the same way the night sky appears to a humanís eye. The lost 3rd dimension is the direction along the line of sight, i.e., time. The farther away a galaxy is, the longer time ago that it existed, because it takes time for light to travel. In order to determine the time at which the galaxy was shining, by forming new stars and/or feeding its central super massive black hole, we need a spectrometer to measure the redshift
At the Terahertz Sensing Group, we are developing a novel submillimeter wave imaging spectrograph DESHIMA. The developments is being done in close collaboration with SRON and Leiden Observatory. The goal is to discover tens of thousands of SMGs over the sky with the camera, measure their distance with DESHIMA, and thereby construct a large, unbiased 3D map of SMGs. This map will give us important insight about the formation and evolution of stars and galaxies. Not only that, we might be able to see giant strings and webs made of SMGs, which trace the cosmic distribution of dark matter
On-chip FilterbankThe key technology of DESHIMA is the on-chip filterbank, which separates incoming photons by their wavelength and distributes them into separate detectors. This is done by using superconducting microresonators as narrow band pass filters. Because the path of the signal is folded ~1000 times inside the microresonator circuit, DESHIMA can cover a broader bandwidth and a wider region of the sky compared to an optical spectrometer with a much larger volume.
Remarkably, the detectors at the output are also nothing but superconducting microresonators, same as the filters, except for being resonant at the readout frequency in the microwave band, and being absorptive for the submillimeter wave signal (a kind of detector which is known as a microwave kinetic inductance detector, or MKID). The nearly identical architecture of the frequency-selecting elements and the detectors leads naturally to an elegant single-chip design as shown above.
Made in Delft, together with SRON and Leiden ObservatoryDESHIMA will be the first instrument that will be developed within the Terahertz Sensing Group in Delft, in close collaboration with SRON and Leiden Observatory. The development of DESHIMA relies heavily on the enthusiasm of students (from electrical engineering and physics) and postdocs. If you are a student who would like to join our team, please contact us anytime.
The DESHIMA project is financed by the Netherlands Organization for Scientific Research (NWO) and the Japan Society for the Promotion of Science (JSPS)