The Silicon Photomultiplier (SiPM) addresses the challenge of detecting, timing and quantifying low-light signals down to the single-photon level.
Traditionally the province of the Photomultiplier Tube (PMT), Avalanche Photodiode (APD), or PIN photodiode with high-gain amplifier, the Silicon Photomultiplier now offers a highly attractive alternative that closely mimics the low light detection capabilities of the PMT while offering all the benefit of a solid-state device - low voltage operation, insensitivity to magnetic fields, mechanical robustness and excellent uniformity of response.
Due to these traits, the SiPM has rapidly gained a proven performance in the fields of medical imaging, hazard and threat detection, biophotonics, high energy physics and LiDAR.
The SiPM is a large parallel array of “microcells” - each comprising a Geiger Mode photon-counting diode and a passive quenching resistor. Incident photons are detected by individual microcells which avalanche and release a fixed quantity of charge whilst the quenching resistor stems the avalanche and resets the microcell. The output of the SiPM is therefore the sum of the charge contributions from all of the microcells and is easily measured above the noise floor of following preamplification circuits. This is one of the key advantages of the SiPM over APD-based technologies.
In October 2012 SensL introduced a revolutionary SiPM structure which combines the standard microcell readout described above with a third electrode providing extremely fast microcell rise & fall times of less than <100ps along with extremely low Capacitance. This "fast-mode" technology works by reading out a small portion of the charge from each Geiger Mode detector directly via a low capacitance electrode - bypassing the combined effects of the passive quenching resistor network. SensL's fast-mode technology is ideally suited to Time Of Flight (TOF) measurements in applications such as Medical Imaging (TOF-PET) and Advanced Driver Assistance Systems (ADAS) where is it used in 3D Imaging and Ranging (LiDAR, gesture recognition etc.).
Because the fast-mode output is proportional it is also being successfully used in Spectroscopic Radiation Detection applications in combination with fast, high light yield scintillators to take advantage of the low capacitance to simplify electronics.
All SensL SiPMs are manufactured in a Tier 1 200mm CMOS wafer foundry with real-time sharing of Process Control Monitoring (PCM) data with SensL's manufacturing engineers in Cork.
Packaging of the Surface Mount SiPMs takes place in high volume facilities typically used to package CMOS imaging sensors used by leading mobile phone and tablet manufacturers. In the case of SensL's J-series Through Silicon Via (TSV) SiPMs the wafer-scale packaging takes place within the Tier 1 CMOS foundry.
Over the years SensL's SiPMs have evolved dramatically - Dark Count Rates have been progressively reduced to just 30kHz/mm² at 2.5V overbias whilst the peak Photon Detection Efficiency can be as high as 51%. At the same time packaging and silicon improvements have broadened the spectral range.
SensL have produced a number of documents intended to introduce new users to SiPM technology and terminology; guidance on how to evaluate and compare SiPMs and an overview of their range of SiPMs intended to help users identify the correct solution for their application.
It is worth highlighting that whilst "Introduction" document provides a good starting point for understanding the basic operation of SiPMs it was produced in 2011 and so does not reflect the performance of the current SiPMs. Nor does it discuss SensL's patented fast-readout third electrode structure.
|Introduction to SiPM Technology|
|How to evaluate and compare SiPMs|
|SensL's product selection guide|