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 a fast-gated single-photon counting module. The single-photon counting module is fabricated in the 0.35-μm HV CMOS technology and coupled to a silicon-photon avalanche diode (SPAD). The integrated 10-μm diameter SPAD has a photon detection efficiency of 5% at a wavelength of 850 nm and a very low dark count rate of 60 cps at room temperature. A compact and very high modulation rate top-emitting GaAs-based VCSEL chip is used to deliver pulsed picosecond 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.