Enhanced Filterbanks for THz On-Chip Spectrometers

Abstract

Terahertz astronomy has been exceptionally unexplored until the last decades due to a technological gap, but exactly at these wavelengths the most distant galaxies appear very bright. Efficient instruments that are capable of spectrometry are essential in understanding the physics of these distant objects. Within the framework of this thesis, an efficient, moderate spectral resolution, on-chip filterbank spectrometer is presented. Several band-pass filter units were investigated and compared, being the directional band-pass filter the most robust and performing. A circuit model is constructed for each of these units and arrayed into a filterbank configuration resorting to microwave techniques. The performance of the filterbank with the circuit model, both with and without realistic losses and tolerances is modeled. A microstrip directional band-pass filter unit has been designed and arrayed into a filterbank chip design. A test filterbank chip based on this design has been fabricated. Due to fabrication issues the detector yield was too poor to allow in-depth and statistically significant measurements. Despite this, the filterbank design is expected to outperform state-of-the-art superconducting filterbanks in terms of coupling efficiency.