Fully Integrated Time-Gated 3D Fluorescence Imager for Deep Neural Imaging

Integrated Neurophotonics: Toward Dense Volumetric Interrogation of Brain Circuit Activity—at Depth and in Real Time

“…Concurrent with our development of integrated photonics for E-pixel arrays, we have also designed and fabricated CMOS photon-counting imaging arrays with the form factor of an implantable shank. These permit fluorescence imaging deep within brain tissue (Figure 9) (Choi et al, 2020;Choi et al, 2019;Lee et al, 2019). In one of our recent prototypes, a Dpixel array consists of 512 single photon avalanche diodes (SPAD) aligned in a linear configuration spanning the length of the shank.…”

“…The 512-pixel SPAD array is fabricated with a 6.3% fill factor, and a pixel pitch of 25.3 um along the length of the shank (Choi et al, 2020;Choi et al, 2019;Lee et al, 2019). Each Dpixel provides a photon detection probability (PDP) larger than 10% in the visible fluorescent spectral band of most biomarkers (500-600 nm), with a median dark count rate of 40 counts per second (cps) at room temperature.…”

“…. Detector-pixel array (D-pixels) based upon visible spectrum angle-selective single-photon avalanche diode (SPAD) detectors: Firstgeneration, minimally invasive photonic neural probes for lens-less functional imaging(Choi et al, 2019;Choi et al, 2020. (c) Images of a SPAD-based D-pixel array in clockwise order: scanning electron micrograph (SEM) of a rectangular CMOS die postprocessed into shanks, waterproof flat flexible cable (FFC) assembly used for in vivo insertion, and shank with an epoxy-based 10um-thick absorption filter coating.…”