Parasitic effects in SQUID-based radiation comb generators

TL;DR

This paper analyzes parasitic effects such as inductance, capacitance, and fabrication imperfections on SQUID-based radiation comb generators, showing how these factors influence device performance and how to mitigate adverse effects.

Contribution

It provides a detailed assessment of parasitic effects in SQUID-based radiation generators and offers guidelines for optimizing fabrication parameters to improve performance.

Findings

Geometrical inductance enhances device performance.

Junction capacitance has negligible impact.

Fabrication errors can be mitigated with proper parameter choices.

Abstract

We study several parasitic effects on the implementation of a Josephson radiation comb generator (JRCG) based on a dc superconducting quantum interference device (SQUID) driven by an external magnetic field. This system can be used as a radiation generator similarly to what is done in optics and metrology, and allows one to generate up to several hundreds of harmonics of the driving frequency. First we take into account how assuming a finite loop geometrical inductance and junction capacitance in each SQUID may alter the operation of this device. Then, we estimate the effect of imperfections in the fabrication of an array of SQUIDs, which is an unavoidable source of errors in practical situations. We show that the role of the junction capacitance is in general negligible, whereas the geometrical inductance has a beneficial effect on the performance of the device. The errors on the areas and junction resistance asymmetries may deteriorate the performance, but their effect can be limited up to a large extent with a suitable choice of fabrication parameters.