Silicon Photomultiplier (SiPM)
Silicon Photomultipliers (SiPM) are arrays of Single-Photon-Avalanche-Diodes (SPAD) operated in Geiger mode, enabling the detection of single photons. Depending on the light source and application, several hundred to thousands of SPADs are connected in parallel into pixels. The summed electrical output of such a pixel is proportional to the number of photons hitting its surface.
The SPAD signals rise very quickly. In order to rapidly reset the diode for the next incoming photon, integrated resistors quench the avalanches. The summed signal is transferred via e.g. through silicon vias (TSV) to the processing electronics that shapes, amplifies and digitizes the signals. Time-to-digital converters (TDC) allow the determination of the arrival time of photons.
Based on this technology principle, various SiPM designs are possible and offer a high technology potential for application specific adaptations.