Cavity mode identification for coherent terahertz emission from a nearly square stack of intrinsic Josephson junctions

TL;DR

This paper identifies the electromagnetic cavity mode responsible for coherent terahertz emission in nearly square stacks of intrinsic Josephson junctions, combining experimental measurements and simulations.

Contribution

It introduces a method to identify the transverse magnetic mode in Josephson junction stacks through emission analysis and scattering spectrum simulation.

Findings

Broadly tunable terahertz emissions observed from nearly square stacks.

Simulation results agree well with measured resonance behaviors.

Wedge-type interferometer effectively measures emitted power independently.

Abstract

Stacks of intrinsic Josephson junctions in Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta }$ emit intense and coherent terahertz waves determined by the internal electromagnetic cavity resonance. We identify the excited transverse magnetic mode by observing the broadly tunable emissions from an identical nearly square stack and simulating the scattering spectrum. We employ a wedge-type interferometer to measure emitted integral power independently of the far-field pattern. The simulation results are in good agreement with observed resonance behaviors as a function of frequency.