Silicon Photomultipliers Signal-to-Noise Ratio in the Continuous Wave Regime

We report on signal-to-noise ratio measurements carried out in the continuous wave regime, at different bias voltages, frequencies, and temperatures, on a class of silicon photomultipliers fabricated in planar technology on silicon p-type substrate. Signal-to-noise ratio has been measured as the ratio of the photogenerated current, filtered and averaged by a lock-in amplifier, and the root mean square deviation of the same current. The measured noise takes into account the shot noise, resulting from the photocurrent and the dark current. We have also performed a comparison between our SiPMs and a photomultiplier tube in terms of signal-to-noise ratio, as a function of the temperature of the SiPM package and at different bias voltages. Our results show the outstanding performance of this class of SiPMs even without the need of any cooling system.