Evidence for a Dual-Source Mechanism of THz Radiation from Rectangular Mesas of Single Crystalline \bm{$\mathrm{Bi_2Sr_2CaCu_2O_{8+\delta}}$} Intrinsic Josephson Junctions

TL;DR

This study provides experimental evidence that THz radiation from Bi-2212 mesas involves dual sources: uniform and non-uniform ac-Josephson currents acting as electric and magnetic sources, synchronized with cavity modes.

Contribution

The paper demonstrates a dual-source mechanism for THz emission, contrasting recent theories, through angular and spectral measurements on single-crystal Bi-2212 mesas.

Findings

Strong evidence for dual-source THz emission mechanism.

Non-uniform ac-Josephson current acts as a magnetic source.

Synchronization with cavity modes at harmonic frequencies.

Abstract

The THz radiation emitted from rectangular mesas of single-crystal $\mathrm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ was studied using angular distribution measurements and Fourier transform infrared spectroscopy. Unlike the recent theoretical predictions, the results provide strong evidence for a dual-source mechanism in which the uniform and non-uniform parts of the $ac$-Josephson current act as electric and magnetic current sources, respectively. The latter synchronizes with cavity modes of the mesa with integral harmonics of the fundamental radiation.