Two-photon Imaging with Silicon Photomultipliers

Silicon photomultipliers (SiPMs) are a class of inexpensive and robust single-pixel detectors with applications similar to photomultiplier tubes (PMTs). We performed side-by-side comparisons of recently-developed SiPMs and a GaAsP PMT for two-photon fluorescence imaging of neural activity. Despite higher dark counts, which limit their performance at low photon rates (<1μs), SiPMs matched the signal-to-noise ratio of the GaAsP PMT at photon rates encountered in typical calcium imaging experiments due to their much lower pulse height variability. At higher photon rates and dynamic ranges encountered during high-speed two-photon voltage imaging, SiPMs significantly outperformed the GaAsP PMT.