Microwave microscopy using a superconducting quantum interference device

摘要

We present results on a near-field scanning probe microwave microscope which is based on the nonlinear behavior of a YBa_2Cu_3O_7 direct-current superconducting quantum interference device (SQUID). Our system has a spatial resolution of about 30 μm and derives its probing field from circulating currents in the SQUID loop. The frequency is set by the Josephson relation and is continuously tunable up to about 200 GHz. By imaging small patterned normal metal thin-film samples of Cu and Nb at 77 K, we have confirmed the operating bandwidth of the system and investigated the nature of the imaging process.