Quantum Dots 101: SWIR Image Sensor 101

Quantum Dots 101: SWIR Image Sensor 101

November 4, 2026

Digital cameras have become so inexpensive and capable that they are built into almost everything, from smartphones to cars to doorbells. Yet conventional cameras primarily capture what our eyes can see. Short-wave infrared (SWIR) imaging can reveal information beyond the visible, from detecting moisture to telling apart materials that look identical. Today it remains expensive and largely limited to specialist markets. Quantum dot (QD) sensor technology could change that by directly integrating QDs with conventional CMOS, thus bringing SWIR imaging onto the same low-cost manufacturing platform used for everyday camera chips.

What is SWIR?

We see the world through visible light ‒ the part of the electromagnetic spectrum the human eye can detect, ranging from about 400 to 700 nanometres (nm). But light extends beyond what we can see. Beyond the red end of the visible spectrum lies the infrared. It begins with the near-infrared (NIR, around 700 to 1000 nm), followed by the SWIR (roughly 1,000 to 3,000 nm), and extends further into mid-wave infrared (MWIR, 3,000 to 5,000 nm) and long-wave infrared (>5,000 nm).

Although SWIR light is invisible to us, it reveals information that ordinary cameras miss. Two types of black plastic that look identical to the eye may appear distinctly different in a SWIR image. Moisture in grain or bruising beneath an apple's skin can also become easier to detect. Unlike thermal imaging, which detects infrared radiation emitted by objects because of their temperature, SWIR imaging typically works more like a conventional camera: it captures light reflected from objects, whether that light comes from the sun or a dedicated SWIR light source. The difference lies in the wavelengths being captured, which reveal a different set of features and material properties.

Unlike thermal imaging, which detects infrared radiation emitted by objects because of their temperature, SWIR imaging typically works more like a conventional camera: it captures light reflected from objects, whether that light comes from the sun or a dedicated SWIR light source. The difference lies in the wavelengths being captured, which reveal a different set of features and material properties.

CMOS Image Sensors: How Cameras Capture Light

At the heart of every digital camera is an image sensor: a chip containing millions of tiny light-sensitive elements called pixels. Each pixel converts incoming light into an electrical signal, and together these signals form the image.

Today, most image sensors use CMOS technology, built on silicon using the same manufacturing processes as computer chips. This allows light detection and processing electronics to be integrated on a single compact chip, making cameras small, fast and energy-efficient. Just as importantly, it makes them economical to manufacture at scale. Since the 1990s, CMOS sensors have largely replaced earlier technologies and are now found in phones, cars, laptops and medical devices, with billions manufactured every year. However, silicon has a fundamental limitation. While it responds to visible and near-infrared wavelengths, its sensitivity drops sharply beyond approximately 1,000 - 1,100 nm. At longer wavelengths, SWIR light generally passes through silicon without being absorbed. Capturing SWIR images therefore requires SWIR-sensitive materials.

However, silicon has a fundamental limitation. While it responds to visible and near-infrared wavelengths, its sensitivity drops sharply beyond approximately 1,000 - 1,100 nm. At longer wavelengths, SWIR light generally passes through silicon without being absorbed. Capturing SWIR images therefore requires SWIR-sensitive materials.

SWIR Image Sensor Technologies

Today, indium gallium arsenide (InGaAs) is the incumbent technology for SWIR imaging. This semiconductor material is sensitive to SWIR light and delivers high sensitivity and excellent image quality. It is well established in demanding industrial, scientific and defence applications.

However, InGaAs sensors are expensive to produce. The light-sensitive InGaAs material is grown on indium phosphide (InP) wafers, which are smaller and considerably more expensive than the silicon wafers used for standard CMOS chips. It is manufactured separately from the silicon chip that reads the image. The two are then connected using hundreds of thousands to millions of tiny electrical connections, adding complexity and cost to the manufacturing process. These connections also limit how small each pixel can be, which restricts image resolution. As a result, InGaAs cameras can cost thousands of dollars - far more than visible-light cameras with similar resolution.

In addition to these cost limitations, standard InGaAs detectors are only sensitive to light up to around 1,700 nm and therefore cover only part of the SWIR. While extended InGaAs detectors can achieve sensitivity beyond this wavelength (up to about 2,500 nm), they come with significant performance and cost trade-offs, due to the increased challenges of manufacturing the material. Researchers have explored alternatives, including germanium-based materials and organic semiconductors. The goal is to develop SWIR sensors that combine good image quality with lower production costs and can be manufactured using scalable semiconductor processes. This is where QD technology has significant advantages.

Researchers have explored alternatives, including germanium-based materials and organic semiconductors. The goal is to develop SWIR sensors that combine good image quality with lower production costs and can be manufactured using scalable semiconductor processes. This is where QD technology has significant advantages.

Quantum Dot CMOS Image Sensor Technology

QDs are tiny semiconductor crystals, only a few nanometres in size. Their exact size determines which wavelengths of light they absorb, allowing their sensitivity to be tuned across the visible and the entire SWIR, including wavelengths beyond the limits of InGaAs. QD CMOS image sensors aim to combine this SWIR sensitivity with the manufacturing advantages of standard CMOS technology.

In a QD CMOS sensor, a thin layer of QDs is integrated as part of a device stack on top of a CMOS chip. The QDs capture SWIR light and convert it into electrical signals, while the CMOS chip reads those signals to create an image. Because this stack can be deposited directly onto a CMOS wafer, it avoids the complex bonding process used in conventional InGaAs sensors and promises to make SWIR cameras simpler and cheaper to manufacture.

Beyond lower manufacturing costs, the technology enables smaller pixels than InGaAs, and therefore higher-resolution images, as well as the ability to capture both visible and SWIR light with a single sensor. While first generation QD CMOS sensors are available today, improving their sensitivity, image quality and long-term stability remain active areas of development and will advance with continued progress in materials optimisation and device integration.

Applications: Where Can Low-cost SWIR Imaging Make a Difference?

As sensors become smaller and more affordable, SWIR technology could reach a wider range of applications and markets.

• Consumer electronics: Compact SWIR sensors could enable new features in smartphones, smart devices and wearables, from advanced biometric sensing to emerging optical health-monitoring applications.
• Automotive: SWIR can complement conventional cameras in pedestrian detection in challenging environmental conditions. Inside the vehicle, it also offers opportunities for improved driver and occupant monitoring under varying lighting conditions.
• Surveillance and defence: SWIR cameras can provide additional visibility in low-light conditions and certain types of haze, supporting long-range surveillance, situational awareness and security applications.
• Machine vision and industrial inspection: SWIR cameras can identify defects, distinguish visually similar materials and assess moisture content. Applications include semiconductor manufacturing, food sorting and plastic recycling.

With advances in QD CMOS technology, the potential for lower-cost manufacturing, tunable wavelength sensitivity and compact sensor designs could make SWIR imaging accessible to a much broader range of products and applications, particularly in markets where the high cost of conventional SWIR cameras has historically limited adoption.

For a deeper look at the technology, download our white paper, or explore our QD materials in our online shop, where we offer a wide variety of SWIR sensitive lead sulphide (PbS) and indium arsenide (InAs) QD materials.