Sub-nanosecond time-gated camera based on a novel current-assisted CMOS image sensor

Time-gated image sensors with (sub-)nanosecond gating times have already found applications in multiple different domains such as 3D Time-of-Flight cameras, Fluorescence lifetime imaging (FLIM) and Tomography. Commercial timegated cameras are based on Image intensified CCDs (ICCD). The photomultiplier tubes used in these ICCDs have a limited quantum efficiency in visible and a fortiori in Near-Infrared (NIR). Furthermore, they are expensive, bulky, fragile and need high voltages to operate. We propose a time-gated camera based on the Current-Assisted Photonic Sampler (CAPS) which integrates the gating mechanism inside a silicon-based pixel without the need for photomultipliers. Due to particular pixel design, sub-nanosecond gating can be achieved while still attaining high quantum-efficiency even in NIR. A first proof-of-concept camera is demonstrated in this paper based on a 32x32-pixel CAPS array with specific timing circuitry to achieve precise and accurate high-resolution sensor gating. Quantitative results about the performance of the camera, such as gating speed and quantum efficiency will be presented and discussed. The cameras capabilities are demonstrated in two experimental setups. The first one: imaging a laser pulse traveling at the speed of light along the field of view. The second setup: making fluorescence lifetime images of two cuvettes containing fluorescent solutions with distinct lifetimes.