Compact sub-nanosecond time-gated camera based on a new 64x64 Current-Assisted Photonic Sampler (CAPS) sensor with improved quantum efficiency

In this paper, we present the tauCAM, a compact sub-nanosecond time-gated video framerate imaging camera, with our new 64x64-pixel Current-Assisted Photonic Sampler (CAPS) sensor. It features gating widths of less than 1 ns with a jitter of less than 60 ps rms on the gating width and less than 50 ps rms on the position. It has a quantum efficiency (QE) of more than 40% for near-infrared wavelengths. It's peak QE is 61% at 675 nm. The sensor is fabricated in a conventional 350 nm CMOS process. We give an overview of the design of the new camera hardware, with characterization of the timing circuitry and gating signals. Furthermore, the new sensor is discussed in detail. The revised pixel design yields improvements in QE, with high QE even for very short gating windows. Additionally, the Instrument Response Function of the pixel is characterized. The capabilities of the tauCAM are demonstrated in an experimental setup where we image a scene that is sequentially illuminated with red, green and blue light, on a nanosecond time scale. Due to its fast-gating mechanism, our CAPS sensor can distinguish and image these colors separately, while the human eye merely sees white illumination.