Passive terahertz imaging with lumped element kinetic inductance detectors

Abstract

Progress towards large format, background limited detector arrays in and around the terahertz or sub-millimetre region of the electromagnetic spectrum has – until recently – been hampered by the complexities in fabrication and cryogenic electronic readout associated with increasing pixel counts. Kinetic inductance detectors or KIDs are a superconducting pair breaking detector technology designed to overcome these complexities. Traditionally, KID arrays have been developed for imaging in astronomy. However, the high sensitivities, broadband responses, fast time constants and high detector counts that are achievable – along with the simplicity of fabrication and readout compared to other contemporary technologies – make them suitable (and in fact desirable) for a variety of applications. This thesis documents the development of a concept instrument to demonstrate KID technology for general purpose imaging applications. Specifically, I present the design, construction and performance of a near background limited, quasi-video rate, passive imaging system based on arrays of Aluminium lumped-element KIDs. The camera operates in two atmospheric windows at 150 GHz (2 mm) and 350GHz (850 μm) with 60 and 152 pixels, respectively. Array fabrication was achieved with a single photolithographic cycle of thin film deposition, patterning and etching. Full array readout is with a single cryogenic amplifier and room temperature FPGA based frequency domain multiplexing electronics. The camera is the first of its kind in applying KID arrays to imaging systems outside of pure astrophysics research and is the result of efforts from the staff and students of the Astronomy Instrumentation Group (AIG) in the School of Physics and Astronomy with support from QMC Instruments Ltd. The system exemplifies the AIG’s world-leading expertise in the development of far-infrared/sub-mm instrumentation as well as QMCI’s vision to provide the highest quality terahertz optical components and detector systems to the global marketplace