Transition Edge Sensors for Far-Infrared Space Science

Superconducting Transition Edge Sensors (TESs) are an outstanding candidate detector technology for the next generation of far-infrared space observatories. Future missions will seek to achieve unprecedented background-limited sensitivities by combining large (>1 m) cold (<4 K) aperture telescopes with many thousands of detectors having Noise Equivalent Power (NEP) of only 10^{-19} WHz^{-1/2}. However, very few TES arrays have so far been developed for these wavelengths, ∼30-200 μm, characterised by an NEP two orders of magnitude lower than necessary in TESs for ground-based microwave astronomy, few-moded optical behaviour and saturation powers of only ∼10 fW. In this thesis, I seek to advance far-infrared TES technology first by demonstrating cryogenic characterisation techniques fundamental to understanding physical behaviour and performance, then by exploring promising innovations in device design. I first describe a cryogenic optical test facility in which TESs are cooled to <100 mK and illuminated with a few-mode infrared field. I implement techniques to shield detectors from stray light, stray magnetic fields and electromagnetic interference, critical to realising optimal performance both in ground-based test systems and ultimately in space, with a particular emphasis on thermal design to eliminate stray light. I demonstrate successful TES operation through the thermal, optical and electrical characterisation of the first TESs for 60-110μm wavelengths, integrated with reflective backshorts and few-mode lightpipes. I then present a new technique for generating a rapidly modulated optical field using a fast infrared source, allowing response rates to changes in illumination to be measured for the first time in these devices. Achieving NEP∼10^{-19} WHz^{-1/2} currently requires long (>600 μm), narrow (≤1.5 μm) TES support legs to limit thermal conductance by diffusive phonon scattering, preventing tight optical packing in arrays. Incorporating elastic filters into shorter legs offers an attractive means to reach low NEP in compact structures with increased performance uniformity. I present the first experimental study of TES supported by phononic interferometers and resonators, patterned into legs only 0.5 μm wide and up to 25 μm long, demonstrating NEPs as low as 5×10^{-19} WHz^{-1/2} suitable for a range of ultra-low-noise TES applications. I conclude by developing elastic travelling wave simulations of a new family of lattice support structures, exploring their potential for enhanced thermal isolation.

Name dc:type.qualificationname

Doctor of Philosophy (PhD)

Level dc:type.qualificationlevel

Doctoral

Grantor dc:publisher.institution

University of Cambridge

Year dc:date.issued

2021

Author dc:creator

• Williams, Emily

Advisor dc:contributor.advisor

• Withington, Stafford

• Transition Edge Sensors
• Superconducting detectors
• Infrared astronomy
• Superconductors
• Space telescopes

Licence

• https://www.rioxx.net/licenses/all-rights-reserved/

Language dc:language

eng

DOI dc:identifier.doi

https://doi.org/10.17863/CAM.89343

OAI identifier oai:identifier

oai:www.repository.cam.ac.uk:1810/341923