The THz spectral regime is one of the last frontiers in detector development for astronomy. At this confluence of infrared and radio techniques, two general approaches are used. Incoherent techniques, including bolometers and photoconductors, have been pushed to array sizes as large as 10,240 pixels. However, incoherent detectors do not preserve phase information of the radiation, and so do not permit high spectral resolution unless they are teamed with dispersing gratings or etalons. Furthermore, when used in a dispersed format, incoherent arrays can no longer offer spatial information in both detector dimensions. Today's coherent detectors, on the other hand, can operate at THz frequencies, but the miniaturization, connectorization, and packaging of the feed horns, receivers, and mixers into a dense array pose very daunting technological challenges. To date, the state of the art in coherent detectors has been a 64-pixel 1-D array operating around 350 GHz.
Dr. Christopher Groppi of the Arizona State University was a key member of the team that developed the afore-mentioned 64-pixel heterodyne array, and he now proposes to extend that development the next logical step, to a small (2x4 pixel) 2-D array. This device will need to clear nearly all of the technological hurdles that will be posed by large 2-D arrays, but on a scale that is manageable and for which materials processing techniques can be affordably tested. With the expertise of team members who are experienced in Superconducting-Insulator-Superconducting (SIS) mixer technology, and the participation of both a graduate student (fabrication, assembly, and testing) and an undergraduate student (machining), Groppi plans a 3 yr development effort capped by use of the new array at a frequency of 660 GHz at the 10-m Heinrich Hertz Telescope. Success would have dramatic implications for the efficiency with which gas species can be mapped in star-forming regions and external galaxies, as well as for remote sensing applications. Funding for this work is being provided by NSF's Division of Astronomical Sciences through its Advanced Technologies and Instrumentation program.
