Operating principles | Main characteristics | Modules & implementation | Tradeoffs & considerations | Product comparison
Description of SiPM product
Silicon photomultipliers from Hamamatsu are called Multi-Pixel Photon Counters (MPPC). These devices are solid state photodetectors that can be used for photon counting and other ultra-low-light applications. The MPPC is comprised of a high-density matrix of avalanche photodiodes (microcells) which, when operated in Geiger mode, generate high internal gain (~106) that enables single photon detection. MPPCs also offer high photon detection efficiency and excellent timing resolution, and have some unique advantages such as low bias voltage operation, ruggedness, resistance to excess light, and immunity to magnetic fields.
Basic operation
The basic element of a silicon photomultiplier (SiPM) is a tiny microcell, which is a series combination of an avalanche photodiode and a resistor. A single channel SiPM device can contain a few hundred to tens of thousands of microcells. These microcells are all connected in parallel, so the SiPM is a two-prong device that produces a photocurrent (there is no 2D information). To operate a SiPM, the user typically applies a reverse bias voltage of 3 to 7 volts over the device's breakdown voltage. This puts the SiPM into Geiger mode. Photons striking a microcell while the SiPM is in Geiger mode will trigger an avalanche of charge carriers inside the microcell, resulting in an output pulse. One microcell fires one pulse at a time while it is avalanching, regardless of the number of incident photons. Two microcells firing at the same time will produce an output pulse with twice the amplitude. We use many microcells so the SiPM can detect many photons at a time.
Figure 1: Equivalent circuit
Key features
- High sensitivity (high gain, high photon detection efficiency)
- Low noise (low dark current, low crosstalk, low afterpulsing)
- Excellent photon counting capability
- Excellent timing resolution
- High resistance to mechanical shock and excess light
- Immunity to magnetic fields
- Low voltage operation and simple readout circuit
- Room temperature operation
- Various microcell sizes, active area sizes, and packaging
- Available as multi-channel arrays
- Available as modules (analog or digital output) or with a starter kit to expedite evaluation