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Development of large terahertz heterodyne receiver arrays for future space observations

PhD ceremony:Y. Gan
When:December 10, 2021
Start:16:15
Supervisor:prof. dr. F.F.S. (Floris) van der Tak
Co-supervisor:dr. J.R. Gao
Where:Academy building RUG
Faculty:Science and Engineering

If one wants to investigate atoms, molecules and dusts in the interstellar medium, one should not make observations using ‘normal’ light, but instead peer them using a very specific type of infrared light, which is the terahertz radiation. The radiation at this specific wavelength contains the fingerprints of various substances and can travel in a long distance to us, but they can only be observed from space because they are blocked by our atmosphere. To increase the observation speed within the limited lifetime of a space telescope, a large terahertz array receiver is favorable. In this PhD thesis, I studied a few key technologies of large terahertz array receivers. To resolve a spectral line signal from space, sensitive terahertz detectors use the signal from a local source to mix with the signal from space. Therefore, special optical components are necessary for coupling the signal from the local source into the detectors. Three chapters in my thesis are the development of the optics for local sources. Furthermore, I also explored a new type of detector, so called hot electron bolometer mixer using MgB2 material, which is different from those commonly used at 4 K low temperature. It can work at a higher temperature (20K), and make the use of a “tiny” cooler, which is considered revolutionary for future space observatories. In the end, I also reported a detailed concept and design study of a 1000-pixel terahertz array receiver, which can act as a reference for next generation of  large arrays.