Third harmonic-mediated amplification in TWPA

TL;DR

This paper demonstrates that the third harmonic in Josephson Traveling-Wave Parametric Amplifiers can be harnessed to enhance performance, doubling bandwidth and increasing gain, contrary to traditional views of harmonics as parasitic.

Contribution

It extends coupled-mode theory to show how the third harmonic can be used to improve amplifier gain and bandwidth, especially in plasma oscillation-based designs.

Findings

Doubling of amplifier bandwidth.

Increase in gain due to third harmonic.

Validation through transient numerical simulations.

Abstract

In Josephson Traveling-Wave Parametric Amplifiers, higher-order harmonics of the pump tone and its sidebands are commonly present and typically regarded as parasitic. Consequently, most design efforts have focused on suppressing these harmonics. In spite of that, motivated by transient simulations, we extend the coupled-mode theory and demonstrate that, contrary to conventional belief, the third harmonic can enhance amplifier performance, improving both gain and bandwidth. We show that the recently developed plasma oscillation-based amplifier is particularly well-suited for exploiting this effect. Their dispersion relation enables us to observe the phenomenon in transient numerical simulations using JoSIM and WRspice. These simulations reveal improvement of the amplifier's performance, specifically the doubling of the bandwidth and an increase in the gain.