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.
Integrating an optical receiver in CMOS optimized for near infrared light (NIR) remains appealing but at the same time challenging due to the deep photon penetration depth. A novel implementation of a light detector is demonstrated in a 350 nm CMOS technology, whereby, through adding a majority current with associated electric field distribution in the silicon detection volume, photo-generated minority electrons get quickly guided to the center of this volume. In the center, a tiny PN junction collects the photo-electrons. The detection speed subsequently increases, NIR light is received with improved responsivity and the detector capacitance gets drastically reduced to femtofarad level. The latter improvement also increases signal-to-noise performance and can be used to trade-off with other design parameters to improve global performance of the opto-electronic system. An optical datacom receiver at 1 Gbps is demonstrated at NIR-wavelength for proving useful Current-Assisted Photodiode detector operation in an actual CMOS system