THz harmonic mixing using YBa₂Cu₃O_7-δnanobridges

Josephson Junctions (JJs) are well-established as THz detectors and mixers, enabling applications from material analysis to space science. Replacing the active element with a simple superconducting constriction reduces fabrication complexity and avoids issues from barrier imperfections. When scaled below the Pearl length, they exhibit similar JJs photo response features, but their behavior is governed by vortex dynamics phase-locked to the applied frequency, providing an effective mechanism for THz detection and mixing.

We report harmonic frequency mixing in the THz regime using HTS nanobridges patterned from from 50 nm thick YBa₂Cu₃O_7−δ (YBCO) films grown on MgO(110). A single step lithography defines a planar spiral antenna with an integrated bridge of cross-section 70 x 50 nm² . Photoinduced current steps appear under single- or a two-source illumination at temperatures in range from 60 K to 77 K. Harmonic mixing is demonstrated using a local oscillator (LO) of 100 GHz and signal sources ranging from 201 GHz to 1.4 THz. In this pilot study, mixing with a 1.4 THz signal (×14) yields ~1 μW output and achieves 20 dB SNR at 1 Hz bandwidth.  These results highlight the potential of nanobridge-based detectors for high-frequency applications enabled by vortex dynamics.