Effective and efficient low-light detection and measurement is critical to many commercial and scientific applications. What differentiates fast, low-light, detection solutions however, is the extent to which individual photons are converted to a detectable signal with low dark current and low excess noise. When the capture minute light signals is critical, it makes sense to rely on the most accurate and most dependable technology. This is where silicon photomultipliers (SiPMs) come in.
SiPMs are solid-state photodetectors that form the basis of many commercial and scientific low-level light detection systems. Composed of arrays of avalanche photodiodes with integrated passive quenching resistors operating in Geiger mode (known as single photon avalanche diodes, SPADs), SiPMs provide high gain, excellent photon detection efficiency, and fast timing in a compact, robust, surface mount package. Their low operating voltage and insensitivity to magnetic fields make them a preferred alternative to traditional photomultiplier tubes (PMTs). SiPM’s compact size and low weight is also advantageous. The combination of these factors means the detectors meet the criteria of many system design engineers seeking to reduce system size, weight and power (SWaP).
The single photon sensitivity, high gain with low excess noise and high photon detection efficiency of SiPMs means they compare favourably with traditional options such as vacuum photomultiplier tubes (PMTs), avalanche photodiodes (APDs), or PIN photodiodes with high-gain amplifiers. SiPMs offer strong performance when it comes to low dark rate count (with DCR being the average count rate recorded without incident light) and crosstalk probability.
Medical Imaging: PET Scanners
In positron emission tomography (PET), the rapid detection of photons generated by gamma interactions with scintillator crystals is critical for image quality and diagnostic accuracy. SiPMs have been widely adopted into PET and Time-of-Flight PET system design enabling improved imaging, with superior timing resolution, enhanced spatial resolution and image noise reduction.
Unlike PMTs, SiPMs are both unaffected by magnetic fields and have no distorting effect on the field. This combination means that SiPMs can be used in combination with MRI systems, making possible combined MR-PET instruments. The compact size of SiPMs also allows for denser detector packing and so more flexible scanner designs.
Key advantages in PET imaging
- High photon detection efficiency for scintillation crystals
- Excellent timing resolution supporting TOF PET
- Magnetic field immunity enabling PET/MRI integration
- Compact size allowing higher detector density and flexible designs
Radiation Detection: Portable Monitors
The low form factor of SiPMs has enabled smaller, more rugged and reliable spectroscopic radiation detection devices. Traditional PMT-based detectors are bulky and fragile with high voltage supplies and short battery life, constraining their use in field applications. The solid-state characteristics of SiPMs means radiation detection systems can be made both more robust and more compact whilst providing stable performance over a wide temperature range.
Their compatibility with various scintillator materials allows efficient detection of gamma rays and neutrons.
The low power requirement of SiPMs extends battery life and simplifies power management in portable devices.
These features have made SiPMs the logical sensing option in personal dosimeters, survey meters, and security screening tools used by first responders, safety inspectors, and border security personnel.
Benefits for portable radiation detection
- Compact, rugged, and field-ready design
- Stable operation across diverse environmental conditions
- Efficient detection of gamma and neutron radiation
- Low power consumption suitable for battery operation
Biophotonics and Life Sciences: Fluorescence and Flow Cytometry
SiPMs are well suited for detecting weak fluorescence signals in applications such as flow cytometry and fluorescence microscopy. These techniques require sensitive, low-noise detectors capable of resolving faint light emitted by labelled cells or biomolecules.
In environments with high event rates, SiPMs offer high gain and fast recovery times. Their compact footprint facilitates integration into benchtop and portable instruments as well as micro-fluidic platforms, aligning with the trend in many areas of instrumentation design towards miniaturisation. Additionally, SiPMs can provide improved linearity and dynamic range compared to PMTs in certain configurations, enhancing quantitative and qualitative accuracy in biological measurements.
Advantages in life sciences applications
- High sensitivity and low noise for weak fluorescence detection
- Fast response supporting high-throughput cell analysis
- Compact size enabling integration into diverse instruments
- Improved linearity and dynamic range for quantitative measurements
The Broadcom Solution
AP Technologies partners with Broadcom in the supply of silicon photomultipliers to OEM system integrators and research laboratories. Broadcom’s SiPMs ensure minimal optical crosstalk and afterpulsing due to a proprietary technology, based on a narrow metal-filled trench (branded NUV-MT), and provide dependable and highly sensitive photon detection. Broadcom SiPMs consistently capture and accurately quantify even minimal photon events – effectively setting the standard for accurate low light detection.
Summary
Silicon photomultipliers offer a unique combination of high sensitivity, compactness, and robustness that addresses the challenges of low-light detection in demanding environments. The advantages they offer is reflected in their growing adoption in medical imaging, radiation monitoring, and life science instrumentation, areas where the need for improved performance, reliability, and ease of integration drive innovation.
Adopting and integrating SiPMs into the development of new systems can allow technical constraints of other, more traditional low-level light detection technologies to be overcome and the establishment of new performance benchmarks.
Further technical information is available in the Introduction to SiPM Technology and other pages in the Support section. You can browse the range of SiPM detectors in the product section.
| To understand the potential of SiPMs for your application, contact Martin at AP Technologies |
