High Frame-Rate Mid-Infrared SPAD Camera

Abstract: Single-photon avalanche diode (SPAD) arrays have transformed optical imaging by enabling photon-counting sensitivity, picosecond resolution, and high frame-rate operation. These capabilities, however, have remained confined to the visible and near-infrared, leaving the mid-infrared, the spectral region hosting the fundamental vibrational signatures of most molecules, largely inaccessible. Here, we demonstrate the first mid-IR SPAD camera by integrating broadband adiabatic frequency upconversion with a 512x512 Silicon SPAD array. This architecture transfers full SPAD functionality to the mid-IR, enabling room-temperature, low-noise, broadband photon-counting imaging. We achieve spectrally resolved mid-IR imaging at frame rates of up to 60,000 frames per second and capture nanosecond-scale laser-induced thermal dynamics via weak mid-IR blackbody emission, revealing spatial-temporal behavior inaccessible to existing technologies. These results establish a scalable platform for photon-resolved, ultrafast thermal and chemical imaging in a spectral range previously inaccessible to high-speed low-light detection.