Scalable Super-Localization Optical Probing of Individual Josephson Junctions in Superconducting Devices

Precise characterization of individual Josephson junctions (JJs) is essential for developing uniform superconducting JJ arrays, particularly in precision metrology, coherent THz sources, and quantum computing. Conventional electrical approaches are often limited by noise, averaging requirements, and the lack of single-junction resolution in large arrays. Here, we introduce a noninvasive optical modulation technique enabling efficient and selective probing of individual JJ characteristics. By modulating the intensity of a light source at high frequencies (50 kHz), we induce controlled changes in JJ properties and extract I_c with high precision using lock-in detection. This method achieves 1% accuracy with only 100 ms of integration, offering comparable precision with substantially reduced acquisition time. Importantly, it enables scalable, parallel superlocalized mapping of JJ arrays through beam steering or multiplexed illumination, allowing identification of local inhomogeneities and defects. Beyond JJs, this approach provides a general framework for spatially resolved probing of emerging quantum materials and devices.