Application of a high-temperature superconducting detector to terahertz imaging

The performance of a high temperature superconducting junction detector is evaluated. The detector has been built to explore applications of terahertz imaging. The detector device is a high-temperature superconductor (HTS) Josephson junction, which is integrated with a thin-film ring-slot antenna. The ring-slot antenna is patterned on a magnesium oxide (MgO) substrate which is compatible with the detector's YBCO superconducting material lattice. A hyper-hemispherical lens made from high resistivity float zone silicon (HRFZ-Si) is mounted on the rear side of the substrate. The lens couples energy from an imaging system onto the antenna which couples the energy into the device. An existing terahertz imaging system is used in conjunction with the detector to allow for the exploration of relevant applications. The imaging system is based on a conventional quasi-optical design with a backward-wave oscillator as the source and raster scans samples for image acquisition. The imaging capability of the system has been assessed by trialing a range of applications in both transmission and reflection modes. Applications explored include imaging concealed weapons in packaging, non-destructive testing of materials, and imaging devices through plastic structures. The results generated by the imaging system demonstrate its capability for these applications.