Coupling broadband terahertz dipoles to microscale resonators

TL;DR

This paper demonstrates a method for spatially mapping the coupling between local terahertz sources on spintronic emitters and resonator modes, enabling tailored THz emission profiles through structured metallic environments.

Contribution

It introduces a technique for mapping local THz source coupling to resonator modes, providing insights into microscopic mechanisms and enabling custom spectral and angular emission control.

Findings

Experimental results match numerical models for bow-tie resonators.

The method reveals THz mode structures in split-ring metasurfaces.

Planar THz sources with tailored emission profiles are achievable.

Abstract

Spintronic emitters are a unique class of terahertz (THz) sources due to their quasi-two-dimensional geometry and thereby their capability to couple to resonator near fields. Global excitation of the emitters often obstructs the intricate details of the coupling mechanisms between local THz dipoles and the individual modes of resonator structures. Here, we demonstrate the spatial mapping of the coupling strength between a local terahertz source on a spintronic emitter and far-field light mediated by a structured metallic environment. For a bow-tie geometry, experimental results are reproduced by a numerical model providing insights into the microscopic coupling mechanisms. The broad applicability of the technique is showcased by extracting the THz mode structure in split-ring resonator metasurfaces and linear arrays. With these developments, planar THz sources with tailored spectral and angular emission profiles are accessible.