Exploring the challenges of a far-infrared post-dispersed polarising Fourier transform spectrometer

Abstract

Recent advances in superconducting far-infrared (FIR) bolometer detectors have resulted in increases to their sensitivity of at least two orders of magnitude over broadband detectors flown on previous far-infrared spaceborne astronomy instruments. Such sensitivity means that observations employing a Fourier transform spectrometer (FTS) will require techniques to reduce the spectral bandwidth of a detector to limit the photon noise. The proposed SPICA SAFARI instrument employs grating spectrometers to post-disperse the light that has been modulated by a polarizing FTS onto a detector array: a post-dispersed polarizing FTS (PDPFTS). This thesis presents the development of a FIR PDPFTS consisting of a FTS and grating spectrometer. The challenges of phase correction given the narrow bandwidth of the PDPFTS were explored and a technique was developed for reliable phase correction. The results show that the PDPFTS works as predicted, and allows one to recover a broadband spectrum at high resolution.