Microwave electric-field imaging using a high-Tc scanning superconducting quantum interference device

Abstract

We have used a 77 K thin-film YBa2Cu3O7 superconducting quantum interference device (SQUID) in a scanning SQUID microscope to image room-temperature sources of high-frequency electric field. We find that time-varying electric fields capacitively induce currents in the SQUID, which in turn are rectified by the nonlinearity of the SQUID current-voltage characteristics, leading to changes in the quasistatic voltage across the SQUID. By observing changes in the voltage modulation depth ΔV of the SQUID as a sample is scanned past the SQUID, we obtain electric-field images in the 1-15 GHz frequency range with a SQUID-to-sample separation of about 80 μm. © 1998 American Institute of Physics.