MICROWAVE ELECTRIC-FIELD IMAGING USING A HIGH-T-C SCANNING SUPERCONDUCTING QUANTUM INTERFERENCE DEVICE

We have used a 77 K thin-film YBa2Cu3O7 superconducting quantum interf erence device (SQUID) in a scanning SQUID microscope to image room-tem perature sources of high-frequency electric field. We find that time-v arying electric fields capacitively induce currents in the SQUID, whic h in turn are rectified by the nonlinearity of the SQUID current-volta ge characteristics, leading to changes in the quasistatic voltage acro ss the SQUID. By observing changes in the voltage modulation depth Del ta V of the SQUID as a sample is scanned past the SQUID, we obtain ele ctric-field images in the 1-15 GHz frequency range with a SQUID-to-sam ple separation of about 80 mu m. (C) 1998 American Institute of Physic s.