Compact fast optode-based probe for single-photon counting applications

We present a compact standalone optode probe integrated with a pulsed Vertical Cavity Surface Emitting Laser (VCSEL) and fast-gated single-photon counting module. The single-photon counting module is fabricated in 0.35 mm HV CMOS technology and coupled to a silicon-photon avalanche diode (SPAD). The integrated 10-mm diameter SPAD has photon detection efficiency of 5 % at wavelength of 850nm and very low dark count rate of 60 counts per second (cps) at room temperature. A compact and very high modulation rate top-emitting GaAs-based VCSEL chip is used to deliver pulsed pico-second light. High intensity short-time reflections, occurring due to the close proximity of the light source and detector, are avoided by fast-gating of the detector which enables the detection of photons in some specified time-windows. A full characterization of the module is done without any cooling, testing both its electric and optical properties. The compactness of the module paves the way for its utilization in a wide variety of single-photon counting applications.