Monolithic superconducting emitter of tunable circularly polarized terahertz radiation

TL;DR

This paper presents a method to generate highly polarized, tunable circularly polarized terahertz radiation from high-temperature superconductor Josephson junctions by controlling surface currents in a monolithic device.

Contribution

It introduces a novel approach to modulate THz polarization using surface current control in a superconducting mesa structure, enabling high polarization and intensity.

Findings

Achieved over 99% circular polarization degree.

Demonstrated electrically controlled polarization modulation.

Consistent numerical and experimental results.

Abstract

We propose an approach to control the polarization of terahertz (THz) radiation from intrinsic Josephson-junction stacks in single crystalline high-temperature superconductor $Bi_2Sr_2CaCu_2O_{8+\delta}$. By monolithically controlling the surface current distributions in the truncated square mesa structure, we can modulate the polarization of the emitted THz wave as a result of two orthogonal fundamental modes excited inside the mesa. Highly polarized circular terahertz waves with a degree of circular polarization of more than 99% can be generated using an electrically controlled method. The emitted radiation has a high intensity and a low axial ratio (AR<1 dB). The intuitive results obtained from the numerical simulation based on the conventional antenna theory are consistent with the observed emission characteristics.