  Several types of Silicon Photomultipliers were exposed to short pulsed laser
light (~ 30 ps FWHM) with its intensity varying from single photon to well
above the number of microcells of the device. We observed a significant
deviation of the output of SiPMs from the expected behavior although such
response curve is considered to be rather trivial. We also noticed that the
output exceeds the maximum expected pulse height, which should be defined as
the total number of pixels times the single photon pulse height. At the highest
light intensity (~ 500 times the number of pixels) that we tested, the signal
output reached up to twice the maximum theoretical pulse height, and still did
not fully saturate.
