Various applications require optical sensors with extremely high sensitivity in order to detect weak light down to the single photon. If the spatial resolution does not have the highest priority, silicon photomultipliers (SiPM) optimally meet this requirement. Silicon photomultipliers are extremely sensitive optical detectors for the measurement of the smallest amounts of light and for the detection of single photons. They are used in various applications and are ideally suited for medical diagnostics or in high-energy physics, they are indispensable for the detection of single particles.
One interesting area is high-energy physics in which the detection of individual particles is indispensable. Another widespread application field of Silicon photomultipliers is in nuclear medicine in the field of positron emission tomography (PET). Here, a radioactive substance is supplied to the body as a marker (tracer) for metabolic activity. With the decay of the substance positrons (positively loaded elementary particles) are formed that destroy themselves in combination with the electrons as their counterparts and release energy in the form of photons. During this process two photons with 180° difference in impulse direction form. These opposite propagating photons hit inside a tube and, by their arrival time, provide information about the place of origin, or positron emission. The differences of the decay rate in the body are of particular interest, because the chosen substances accumulate, for example, on tumor cells, marking areas with high intensities suspected tumor areas.