Optical characterization of OMT-coupled TES bolometers for LiteBIRD
Journal of Low Temperature Physics Springer Nature 209:3-4 (2022) 396-408
Authors:
J Hubmayr, Par Ade, A Adler, E Allys, D Alonso, K Arnold, D Auguste, J Aumont, R Aurlien, Je Austermann, S Azzoni, C Baccigalupi, Aj Banday, R Banerji, Rb Barreiro, N Bartolo, S Basak, E Battistelli, L Bautista, Ja Beall, D Beck, S Beckman, K Benabed, J Bermejo-Ballesteros, M Bersanelli, J Bonis, J Borrill, F Bouchet, F Boulanger, S Bounissou, M Brilenkov, Ml Brown, M Bucher, E Calabrese, M Calvo, P Campeti, A Carones, Fj Casas, A Catalano, A Challinor, V Chan, K Cheung, Y Chinone, C Chiocchetta, Se Clark, L Clermont, S Clesse, J Cliche, F Columbro, Ja Connors
Abstract:
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/SiNx/Nb microstrip at 100 mK and over the frequency range 200–350 GHz, which is comparable to values previously reported in the literature.
