Astronomers use far-infrared spectrometers to study the composition and movements of galaxies and gas clouds. Researchers from TU Delft, SRON, and the University of Cologne are therefore developing new spectrometers based on superconducting resonators, which split the colors of light. They have now made the frequencies to which the resonators are sensitive four times more accurate.
They work in a way somewhat similar to the human ear, where tiny hair cells are set in motion by sound waves and send a signal to our brain. Each hair cell—or resonator in the spectrometer—detects a different frequency.
The researchers want to place a large number of resonators side by side so that they can measure a wide frequency range simultaneously. But in practice, the resonators did not tune to the intended frequencies with sufficient precision. There were small random and systematic deviations in the frequencies, which led to gaps.
The researchers investigated the resonators’ manufacturing process—electron beam lithography—in which an electron beam etches patterns onto a chip. They discovered that a smaller step size of the electron beam results in more accurate frequencies. This allowed them to increase the precision of the frequencies by a factor of about four. Telescope instruments such as DESHIMA and TIFUUN can benefit from this discovery.
Publication
The associated publication in APL Engineering Physics has been selected as Editor’s choice.
G. G. Olde Scholtenhuis, D. J. Thoen, J. J. A. Baselmans, K. Karatsu, L. H. Marting, S. Vollebregt, and A. Endo, “Enhanced electron-beam lithography to reduce the frequency scatter of 200–400 GHz superconducting microstrip resonators for on-chip filterbank spectrometers,” APL Engineering Physics 2, 016101 (2027) https://doi.org/10.1063/5.0345761