THz microscope for three-dimensional imaging with superconducting Josephson junctions

Abstract

Superconducting Josephson junctions have a wide range of applications ranging from quantum computing to voltage standards, and they may also be employed as versatile sensors for high-frequency radiation and magnetic fields. In this work, we present a unique measurement setup utilizing a single Josephson junction on a cantilever for high-resolution spatial measurements of spectroscopically resolved THz and microwave field distributions. This THz microscope can be utilized to measure power and frequency of electromagnetic radiation from ∼1 GHz to 5 THz. It may also be used to measure static magnetic fields and provide topological scans of samples. The samples can be both actively radiating or passively irradiated at either room temperature or cryogenic temperatures. We review the measurement setup of the THz microscope and describe the evaluation of its measurement data to achieve three-dimensional visualizations of the field distributions. The diverse capabilities of this unique tool are demonstrated by its different measurement modes with measurements of field distributions at 20 GHz and 1.4 THz, spectroscopically resolved THz measurements, and magnetic field measurements.