Silicon photomultiplier(SIPM) | SIMTRUM Photonics Store

The silicon photomultiplier (SiPM) detector with amplification is composed of a large number of avalanche photodiodes (APDs) operating in Geiger mode. It has high photon detection efficiency in the ultraviolet to visible light range. Each pixel can be biased above the breakdown voltage, and higher PDE and gain can be achieved at high bias voltages, making it suitable for low-light detection. Under low bias voltage, lower dark counts and crosstalk probabilities can be obtained.

Unlike photomultiplier tubes (PMT), SiPM detectors are not affected by magnetic fields and will not be damaged by ambient light. Both detectors can amplify very weak signals and have similar gain levels, but PMT usually covers a larger active region, while SiPM is more compact in size. Although the two detectors have comparable detection efficiency, the working voltage of SiPM is much lower, which can provide a larger dynamic range.

Applying an external bias voltage to the SiPM detector can make the APD pixels operate at a voltage higher than their breakdown voltage, thereby generating a strong electric field. When a single photon is absorbed, electron-hole pairs are produced. The electric field accelerates the electrons, and secondary electrons are generated through collision ionization. The resulting avalanche constitutes the gain of the SiPM detector, and the avalanche varies according to the applied bias voltage.

 The SiPM detector can improve the gain and photon detection efficiency (PDE) of the detector by adjusting its bias level. However, increasing the bias level will also increase crosstalk behavior and amplify the dark current, thereby increasing the dark count. Increasing the bias level will also improve the transit time extension and reduce the time required for the output signal after the light is incident. Generally speaking, for applications with high gain or PDE, a higher bias level can be set, while for applications requiring low noise, a lower bias voltage can be set.

For different models of SiPM, the pixel size, active area and sensitivity are all different. Generally, SIPMs with large pixel sizes can offer higher gain and PDE, while those with small pixel sizes can provide faster response speeds and a wider dynamic range. Sipms with larger active regions are more suitable for applications that require a wider dynamic range, while smaller active regions offer higher response speeds and lower dark counts. The PDE of the SiPM detector is comparable to the quantum efficiency (QE) of the photomultiplier tube (PMT). However, the SiPM detector can provide a larger dynamic range.

• Geiger mode: In this mode, the operating voltage of the diode is slightly higher than the breakdown threshold voltage. Therefore, a single electron-hole pair (generated by absorbing photons or thermal fluctuations) can trigger a strong avalanche. Each pixel in the SiPM detector contains the APD in Geiger mode.
• Dark count rate: The average rate at which counts are recorded in the absence of any incident light, and it determines the minimum count rate caused by real photons. It can be suppressed by using a cooling detector.
• Dead time: It is the time interval that the detector spends in the recovery state. During this period, the detector is insensitive to incident photons. The simultaneous dead time of multiple pixels in the SiPM detector will affect the dynamic range of the detector. 
• Post-pulse: During an avalanche, some charges can be trapped in the high-field region of the pixel. When these charges are released, they will trigger an avalanche. The lifetime of these trapped charges is only a few tenths of a microsecond. Therefore, it is very likely that a post-pulse will occur directly after the signal pulse.
• Crosstalk: Crosstalk occurs when an avalanche generated by one pixel triggers a secondary avalanche of adjacent pixels.

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Performance

Components

Visible Single Photon Detector(SPD)

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