Optical characterization of OMT-coupled TES bolometers for LiteBIRD

Journal article

Feedhorn- and orthomode transducer- (OMT) coupled transition edge sensor (TES) bolometers have been designed and micro-fabricated to meet the optical specifications of the LiteBIRD high frequency telescope (HFT) focal plane. We discuss the design and optical characterization of two LiteBIRD HFT detector types: dual-polarization, dual-frequency-band pixels with 195/280 GHz and 235/337 GHz band centers. Results show well-matched passbands between orthogonal polarization channels and frequency centers within 3% of the design values. The optical efficiency of each frequency channel is conservatively reported to be within the range 0.64 - 0.72, determined from the response to a cryogenic, temperature-controlled thermal source. These values are in good agreement with expectations and either exceed or are within 10% of the values used in the LiteBIRD sensitivity forecast. Lastly, we report a measurement of loss in Nb/SiN_x/Nb microstrip at 100 mK and over the frequency range 200–350 GHz, which is comparable to values previously reported in the literature.

Authors: Hubmayr, J; Ade, PAR; Adler, A; Allys, E; Alonso, D

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Springer Nature
• Journal: Journal of Low Temperature Physics
• Volume: 209
• Issue: 3-4
• Pages: 396-408
• Publication date: 2022-09-05
• Acceptance date: 2022-07-24
• DOI: 10.1007/s10909-022-02808-7
• EISSN: 1573-7357
• ISSN: 0022-2291
• Language: English
• Keywords: low temperature detector; CMB; TES; OMT; bolometer