Demonstration of an optical microwave rectification by a superconducting diode with near 100% efficiency

Abstract: Superconducting electronics offer significant advantages in speed and power efficiency for next-generation computing and communication systems. However, their practical deployment is limited by the absence of simple, efficient, and scalable superconducting counterparts to key semiconductor components. In this work, we investigate diodes based on planar Josephson junctions fabricated from a conventional niobium superconductor. The nonreciprocity in these diodes arises from the self-field effect induced by the geometrical asymmetry of the junction. By deliberate tuning of the junction parameters, we achieved effectively infinite nonreciprocity (within experimental resolution), characterized by a complete suppression of the superconducting critical current in one direction while maintaining a significant current in the opposite direction. The key novelty of this work lies in the demonstration of the optical diode effect. We observed threshold-free rectification of 75 GHz microwave radiation, indicating that these diodes exhibit near-ideal optical nonreciprocity. Our results open new avenues for ultrafast superconducting electronics and lay the groundwork for wireless sub-THz signal processing.