High frequency parametric amplification based on the non-linear dynamics of superconductors

Abstract

Low noise amplifiers (LNAs) are critical components of the receivers that are used for radio and microwave astronomy. In a typical direct amplification system, the radiation that is collected by an antenna and focussed by a series of mirrors must be amplified by a chain of amplifiers within the receiver prior to any further processing. The noise and gain performance of the first LNA in this amplifier chain has the most significant impact on the total signal to noise ratio of the output signal, which can greatly influence the quality and speed at which the observatory can collect its data. Typically, high electron mobility transistor (HEMT) based LNAs have been used for this purpose but these are only suitable for applications below around 100 GHz since their gain and noise performance becomes inadequate at frequencies above this mark. For higher frequency applications, a receiver comprised of a superconducting mixer as the first component is employed to down covert the signal to a lower frequency at which an LNA with a significantly better gain and noise performance can be used. The best of these transistor based LNAs have gains of 20 dB and noise at around 5 to 10 times the quantum noise limit over up to an octave of bandwidth up to 20 GHz. In the last decade, significant development has been carried out on parametric amplifiers (paramps) that make use of nonlinear inductance of Josephson junctions or the kinetic inductance of thin superconducting films. These types of amplifiers have been demonstrated to show high gain over multiple octaves of bandwidth when engineered into travelling wave structures with noise performance nearing the quantum limit. Resonant paramps operate over a narrow bandwidth and routinely reach gains of over 20 dB with noise performance at the quantum limit. Most of this paramp development has been focussed on frequencies below 30 GHz where the dielectric loss of the substrate, and the losses of the necessary interconnects and transitions can be managed. However, if such paramps could be realised at frequencies of over 100 GHz with a gain of over 20 dB and noise performance near the quantum level over a similar bandwidth of operation as the best mixer and HEMT LNA pair (which are predominantly limited by the performance of the LNA) then these paramps could significantly improve the overall performance of the receiver. In addition when considering operation at 4 K there is potential of reducing power dissipated by these paramp at the coldest temperature stages of the receiver which may allow for an increase in the overall available cryogenic budget. This project aims to demonstrate parametric amplification using transmission lines that can be scaled to hundreds of GHz while maintaining low losses. Structures such as circular waveguide and ridge gap waveguide are used to demonstrate Josephson and kinetic inductance type paramps, respectively. Initially narrowband resonant amplifier at 30 GHz are demonstrated, followed by a description of the design of a wide band kinetic inductance variant with ridge gap waveguide operating at a bandwidth of 75 to 110 GHz. An additional goal of this project and thesis is to provide a practical guide for future paramp designers that includes the fundamental theory of superconductivity and parametric amplification, simulation methods of superconducting devices in 3D electromagnetic and 2D circuit solvers, as well as paramp fabrication and cryogenic testing techniques.

Date of Award	1 Aug 2023
Original language	English
Awarding Institution	The University of Manchester
Supervisor	Danielle George (Supervisor) & Lucio Piccirillo (Supervisor)