Dual-mode, in-pixel linear and single-photon avalanche diode readout for low-light dynamic range extension in photodetector arrays

This paper presents an approach for combining linear and single-photon avalanche diode operation in a single pixel to enhance low-light dynamic range of a photodetector array. Pulse frequency modulation and avalanche pulse counting provide in-pixel digitization for both operation modes, enabling full parallel measurement across the array. An 8×8 array architecture is fabricated in standard 180 nm CMOS and demonstrates 85 dB optical dynamic range and a maximum low-light frame rate of 130 Hz. This approach represents the first reported photodetector array architecture supporting both linear and single-photon diode operation in each pixel.