Radiation comb generation with extended Josephson junctions

TL;DR

This paper introduces a Josephson radiation comb generator using extended Josephson junctions driven by magnetic fields, capable of producing a broad spectrum of harmonics for applications in metrology and signal processing.

Contribution

It proposes a novel Josephson radiation comb generator based on extended junctions with magnetic flux control, enabling generation of multiple harmonics and different spectra.

Findings

Up to hundreds of harmonics generated at 50 GHz

Output power reaches 10 pW at 50 GHz

Multiple geometries allow spectrum customization

Abstract

We propose the implementation of a Josephson radiation comb generator (JRCG) based on an extended Josephson junction subject to a time dependent magnetic field. The junction critical current shows known diffraction patterns and determines the position of the critical nodes when it vanishes. When the magnetic flux passes through one of such critical nodes, the superconducting phase must undergo a $\pi$-jump to minimize the Josephson energy. Correspondingly a voltage pulse is generated at the extremes of the junction. Under periodic driving this allows us to produce a comb-like voltage pulses sequence. In the frequency domain it is possible to generate up to hundreds of harmonics of the fundamental driving frequency, thus mimicking the frequency comb used in optics and metrology. We discuss several implementations through a rectangular, cylindrical and annular junction geometries, allowing us to generate different radiation spectra and to produce an output power up to $10$~pW at $50$~GHz for a driving frequency of $100$~MHz.