Feedback-controlled transition-edge sensor bolometers in a far-infrared double-Fourier interferometer

The far-infrared Universe provides substantial insights into the formation of stars and planetary systems, the assembly history and evolution of galaxies, the origins of the Universe, and the search for life. Despite its great scientific potential, the far-infrared Universe remains relatively unexplored with the degree of spatial resolution that is available in observations at other wavelengths. Double-Fourier spatial-spectral interferometry provides a promising path to achieve transformative spatial resolution in far-infrared observations. To further study this technique and improve on its technology readiness, we have constructed a far-infrared double-Fourier interferometry testbed that is coupled to a unique detector array of feedback-controlled transition-edge sensor bolometers. To fully understand measurements made with the interferometry testbed and ensure that these are well-calibrated, the detector system must be understood and characterised at a technical level. The detector array itself is a bespoke system with a substantial parameter space that can be optimized for different use-cases which has made this a daunting task. This thesis centres on the experiments I have conducted to characterise, calibrate, and optimise the detector system both in a general sense and in the context of the double-Fourier instrument. Through this investigation of the detector system, I have reduced the spectral noise of the double-Fourier interferometry testbed by 70%. Throughout this work, I review the concepts and theory related to measurements made with Fourier transform spectrometers and double-Fourier interferometers (Chapter 2). Additionally, I discuss transition-edge sensor bolometers and introduce the feedback-controlled bolometer system (Chapter 3). I have included a detailed discussion of my experiments to chracterise the measurement process of the detector array, optimise its noise performance, and tune its response to optical modulation (Chapter 4). I also provide a