Harmonic Mixing Using a HTS Step-Edge Josephson Junction at 0.6 THz Frequency

A high-temperature superconducting (HTS) terahertz (THz) heterodyne mixer based on a thin-film antenna-coupled YBa
₂
Cu
₃
O
_7−
x
step-edge Josephson junction is presented. The frequency down-conversion from 0.6 THz to an intermediate frequency (IF) of 2 GHz was achieved using high-order harmonic mixing of a local oscillator (LO), thus removing the need to use a second THz source as the LO pumping source. The DC and RF characteristics of the harmonic mixer as well as the relationship of the IF output power versus the harmonic number were experimentally studied and compared with simulated results. Most of our measurements were made at 40 K, but we also observed stable harmonic mixing at 77 K which we believe has not been reported previously in HTS junction mixers.