  This study investigates the characteristics of Silicon Photomultipliers
(SiPMs) with different pixel densities, focusing on their response across a
wide dynamic range. Using an experimental setup that combines laser source and
photomultiplier tubes (PMTs) for accurate light intensity calibration, we
evaluated SiPMs with pixel counts up to 244,719 and pixel sizes down to 6
micrometers. To complement the experimental findings, a "Toy Monte Carlo" was
developed to replicate the SiPMs' reponses under different lighting conditions,
incorporating essential parameters such as pixel density and photon detection
efficiency. The simulations aligned well with the experimental results for
laser light, demonstrating similar nonlinearity trends. For BGO scintillation
light, the simulations, which included multi-firing effect of pixels, showed
significantly higher photon counts compared to the laser simulations.
Furthermore, the simulated response derived in this research offer a method to
correct for SiPM saturation effect, enabling accurate measurements in
high-energy events even with SiPMs having a limited number of pixels.
