Cutting-Edge Photon Detection with Broadcom Sensors

Photon detection allows devices to perceive what is normally invisible, enabling breakthrough applications in automotive safety, medical imaging, robotics, and industrial automation. Detecting individual photons allows for real-time detection of tiny signals, unlocking capabilities from precise distance measurements to early disease detection.

Invented in the 1930s, photomultiplier tubes (PMTs) were the gold standard for detecting photons, but their fragile glass vacuum tubes were too large and difficult to integrate into key applications such as cars, drones, handheld equipment, or consumer devices.  Solid-state avalanche photodiodes (APDs) are more practical but don't have the sensitivity of PMTs.

When product designers need a chip-scale alternative that matches the sensitivity of a PMT and the practicality of an APD, they can turn to silicon photomultipliers (SiPMs), the next generation in photon detection. Broadcom's AFBR‑S4 SiPM family provides cutting-edge photon detection in a form that designers can readily integrate into LiDAR, medical scanners, industrial sensors, or other in-demand applications.

Lighting up innovation

Light can convey crucial information like distance, motion, chemistry, and radiation through each photon. Detecting these photons, especially when they’re scarce or arrive instantaneously, is what enables technologies such as LiDAR in self-driving cars, advanced medical scanners, and ultra-precise industrial sensors.

The challenge is that photons are incredibly small and fleeting, so specialized detectors are needed to capture and amplify them into a usable signal. PMTs convert a single photon into an electron, amplifying it through electrodes in a vacuum tube to produce a measurable electrical pulse. While sensitive and low noise, they don’t fit easily into modern compact systems.

APDs provide a more practical, solid-state alternative that amplifies photons through an internal avalanche process in a silicon diode for a smaller, faster solution. However, they struggle to reliably detect single photons in very low-light conditions, so weak light produces a proportionally weak signal.

SiPMs detect single photons like a PMT, but in a compact, low-voltage, and rugged chip that makes even the faintest light instantly measurable. They are built from arrays of tiny microcells, each operating in Geiger mode so that a single photon produces a full, uniform electrical pulse.

Each microcell essentially functions like a digital switch that flips on the moment it catches a photon. After firing, the cell resets and is ready for the next photon, allowing a sensor with thousands of cells working together to count individual photons and handle brighter light signals.

Compact, high-performance photon detection

Broadcom’s AFBR‑S4 SiPM family combines single-photon sensitivity, fast timing, and robust performance in a compact, practical package to simplify the challenge of integrating advanced light detection into market-ready products.

Broadcom's AFBR‑S4E001 evaluation kit (Figure 1) can help product designers quickly bring SiPM-based applications to market. It provides a ready-to-use platform for testing, prototyping, and integrating AFBR‑S4 sensors without the need to design custom circuitry. This reduces development risk, allowing iteration on both hardware and software before committing to custom PCB layouts or production designs.

Figure 1: The AFBR‑S4E001 evaluation kit includes a mid-range SiPM component and a preamplifier board with two 50 Ω outputs. (Image source: Broadcom Limited)

The evaluation kit includes supporting software and reference designs, so engineers can explore system-level behavior, validate optical coupling strategies, and experiment with array configurations. Designers can connect the SiPM array to standard interfaces, experiment with bias voltage, and measure key performance parameters like photon detection efficiency, timing, and noise under real-world conditions.

Designers can also take advantage of flexible formats in the AFBR‑S4 series, including:

The AFBR-S4N22P014M (Figure 2) is a very compact option with 2,464 microcells per output element in an active array area of 2 mm² for space-constrained applications such as handheld scanners or car bumper modules.

Figure 2: The AFBR-S4N22P014M provides a compact SiPM option for space-constrained applications and can be tiled to cover larger areas. (Image source: Broadcom Limited)

The AFBR-S4N44P014M (Figure 3) increases the number of microcells to 8334 in an active array area of 13.47 mm² for higher photon-counting capacity and improved sensitivity. It's a versatile option for applications such as small-footprint LiDAR, medical imaging, and industrial sensors.

Figure 3: The AFBR-S4N44PP014M SiPM sits in the midrange of the Broadcom family. One of these sensors is included in the AFBR‑S4E001 evaluation kit. (Image source: Broadcom Limited)

The AFBR-S4N66P014M (Figure 4) scales further, with 22,428 microcells in a 36 mm² active array that maximizes photon detection efficiency and signal-to-noise performance. It's suitable for applications that demand both high sensitivity and a larger sensing surface, such as advanced medical imaging and long-range automotive or 3D mapping LiDAR.

Figure 4: The AFBR-S4N66P014M is the largest member of the Broadcom family and provides long-range, high-resolution photon capture. (Image source: Broadcom Limited)

Broadcom engineered these devices to minimize dark counts, crosstalk, and afterpulsing, ensuring that signals remain clean even in challenging environments.

Conclusion

Broadcom’s AFBR‑S4 SiPMs enable designers to integrate high-performance light sensing into various applications, such as automotive LiDAR and medical imaging. The AFBR‑S4 series offers small, midrange, and large variants, along with the AFBR‑S4E001 evaluation kit for rapid prototyping. As such, designers can optimize sensitivity, speed, and footprint to innovate in markets where precise light detection is crucial.