Phase-resolved visualization of radio-frequency standing waves in superconducting spiral resonator for metamaterial applications

TL;DR

This paper introduces a phase-sensitive laser scanning microscopy method for visualizing microwave standing waves in superconducting spiral resonators, enabling detailed study of metamaterial properties at cryogenic temperatures.

Contribution

A novel phase-resolved microwave imaging technique using laser scanning microscopy that surpasses previous methods in resolution and phase sensitivity for superconducting resonators.

Findings

Visualized standing wave patterns up to the 38th eigenmode

Demonstrated phase-sensitive contrast in microwave imaging

Enhanced understanding of electromagnetic field distribution in superconducting metamaterials

Abstract

Superconducting microcircuits and metamaterials are promising candidates for use in new generation cryogenic electronics. Their functionality is largely justified by the macroscopic distribution of electromagnetic fields in arranged unit cells, rather than by the microscopic properties of composite materials. We present a new method for visualizing the spatial structure of penetrating microwaves with microscopic resolution in planar superconducting macroscopic resonators as the most important circuit-forming elements of modern microelectronics. This method uses a low-temperature laser scanning microscope that examines the phase (i.e., direction) and amplitude of local radio-frequency currents versus the two-dimensional coordinates of the superconducting resonant structure under test. Phase-sensitive contrast is achieved by synchronizing the intensity-modulated laser radiation with the resonant harmonics of the microwave signal passing through the sample. In this case, the laser-beam-induced loss in the illuminated area will strongly depend on the local phase difference between the RF carrier signal and the spatially temporal structure of the focused laser oscillation. This approach eliminates the hardware limitations of the existing technique of radio-frequency microscopy and brings the phase-sensitive demodulation mode to the level necessary for studying the physics of superconducting metamaterials. The advantage of the presented method over the previous method of RF laser scanning microscopy is demonstrated by the example of the formation of standing waves in a spiral superconducting Archimedean resonator up to the 38th eigenmode resonance.