Colloidal Quantum Dot SWIR Image Sensing
In a series of blog posts, we are aiming to cast light on the benefits of high resolution imaging using short-wave infrared radiation (SWIR) and how colloidal quantum dots (CQDs) are poised to impact this market. Starting from the applications, we will explore advantages of imaging at different wavelengths, followed by a discussion of the current technology to address this market. Further, we will take a deep dive into CQD sensor technology discussing Nanoco’s current position in the market, as well as future materials developments. This first post explores some of the general principles of SWIR imaging and highlights its potentials with images we recently acquired from a collaboration with Emberion, using Nanoco’s HEATWAVE® QDs.
SWIR typically refers to radiation in the electromagnetic spectrum with wavelengths between 1.0 – 3.0 µm. While not visible to the human eye, SWIR shares more of the properties of visible light over its longer wavelength relatives, such as MWIR and LWIR (mid- and long-wavelength infrared, respectively), which are predominantly emitted by objects. Like visible light, SWIR interacts with matter based on reflection and absorption, facilitating its technological use for high resolution imaging applications with features, such as high contrasts and shadows.
Compared to shorter wavelength alternatives, SWIR light exhibits distinct advantages over visible light that can be leveraged in a variety of environmental imaging scenarios. For example, SWIR experiences less scattering from fine airborne particles, such as haze, smoke or fog, as demonstrated in the images below. Under normal visible light imaging, parts of the scene are obscured by smoke, particularly at the front of the image. In contrast, SWIR imaging – here 1000 – 2000 nm – provides a clear image of all features in the frame, and also allows the viewer to identify the source of the smoke, the active fire.
This scene demonstrates that using SWIR can provide improved imaging tools that enable better visibility through adverse environmental conditions. Another important property of SWIR is its strong and specific absorption by water, which can be targeted using SWIR sensors. This enables imaging-based water detection, opening up a wide range of interesting applications—some of which will be explored in more detail in the next post. Outside of environmental imaging, SWIR imaging is also relevant in more controlled industrial environments. Due to its varying interaction with different materials, as well as its non-invasive optical nature, SWIR imaging presents an ideal solution for a number of quality control applications. For example silicon – which is opaque in the visible – becomes transparent in the SWIR, enabling active imaging during semiconductor processing (see image below – silicon wafer recorded by visible and SWIR camera).
Images provided by Emberion, using Nanoco’s HEATWAVE® QDs
This series of posts will allow us to explore some of the use cases of SWIR imaging in more detail, as well as providing a better understanding of the technology and the unique capabilities that CQD image sensing has to offer.
In the meantime, if you’d like to find out more about Nanoco’s work in this area, please come and see us at the SPIE Defense & Commercial Sensing show in Orlando, starting on 13th April 2025. We have a contributed talk by Anish Priyadarshi, our Device Team Leader, in the Osceolla Ballroom B on the “Progress in the Development of Quantum Dots for SWIR Image Sensing Applications” on Monday 14th April at 11.40 am.