Shortwave infrared (SWIR) imaging, which captures light that is invisible to the human eye, is transforming the effectiveness of systems in many fields, such as medical analysis and industrial inspection, by enabling high-contrast imaging beyond the capabilities of visible light-based methods. These innovations have been driven by upgrades and reduced cost of SWIR system components, including detectors, light sources, and interference-coated filters. A surgeon uses a portable fluorescence imaging device during breast removal. Courtesy of RomanZajets/Shutterstock. SWIR imaging uses a portion of the electromagnetic spectrum, covering wavelengths between approximately 900 and 2500 nm. These wavelengths of light penetrate more deeply into biological tissue, with reduced scattering, compared with shorter wavelengths in the visible range. This can lead to improved image resolution, particularly in dense or complex tissues, such as liver or breast tissue, and makes SWIR ideal for imaging biological structures clearly. Additionally, working in the SWIR range has the benefit of minimizing signal interference generated from autofluorescence — natural tissue light emissions due to light absorption by intrinsic molecules in the sample. Unlike in the ultraviolet, visible, and near-infrared regions, autofluorescence emission is significantly diminished in the SWIR range, and its absence results in sharper, higher-contrast images. These properties make exploiting the SWIR range viable for biological imaging that requires high contrast and minimal background noise. Advancements in components SWIR instrumentation relies on three essential components: light sources, detectors, and interference-coated filters. Light sources operating in the SWIR spectrum have undergone a significant transformation during the last 10 years. Historically, these sources, including lasers and LEDs, were bulky, inefficient, and prohibitively expensive, limiting their adoption and practicality for many laboratory or clinical settings. Now, modern SWIR light sources are smaller, more efficient, and cost-effective with longer lifetimes. Compact designs have enabled SWIR light sources to be integrated into portable and point-of-care devices, such as cameras and microscopes. At the same time, improvements in sensor efficiency with the introduction of new materials have reduced power consumption and heat generation. These advancements not only decrease operational costs but also make SWIR imaging practical for applications requiring precise and reliable illumination, such as surgical imaging and noninvasive diagnostics. The reduction in the cost of SWIR light sources has further enabled clinical and research facilities in limited resource areas to adopt the technology. Detectors, particularly indium gallium arsenide (InGaAs) arrays, are another critical component of SWIR imaging systems. These detectors capture light in the SWIR spectrum and convert it into electrical signals for analysis. Innovations in detector construction, such as Sony’s SenSWIR technology, have led to quantum efficiencies of >75% improving photon-to-electron conversion and reducing noise. This enhancement allows for clearer imaging, even in low-light conditions or high-speed applications. In addition to performance improvements, sensors used in InGaAs detectors have been significantly reduced in cost, making them more accessible in areas aside from high-budget research environments. As a result, portable SWIR devices are becoming more common, enabling their use in fieldwork and clinical settings. New detector technologies have the potential to create further performance improvements and drive cost reductions. For example, quantum dots can be integrated into integrated circuits, and organic photodiodes are not as brittle as their inorganic counterparts. Coated SWIR filters Optical filters are at the heart of high-performance SWIR imaging systems, selectively transmitting specific wavelengths while blocking out-of-band light that interferes with image clarity. Achieving both high transmission (Figure 1) and deep blocking (Figure 2) is critical for applications requiring exceptional precision, such as deep-tissue imaging and biomarker identification. These dual-performance requirements of high transmission and deep blocking define the utility of SWIR filters. Figure 1. The transmission performance of a dual-band SWIR filter. Courtesy of Chroma Technology Corp. Figure 2. The out-of-band blocking performance of a dual-band SWIR filter. Courtesy of Chroma Technology Corp. High transmission ensures that sufficient light reaches the detector, maximizing the signal capture in applications such as fluorescence imaging. Advanced coatings applied to filters reduce internal reflection and absorption, allowing more photons to reach the detector. In addition to maximizing photon delivery, high transmission helps improve the speed and accuracy of imaging systems. When light transmission is efficient, imaging systems can operate effectively even in low-light conditions, such as live-cell imaging or surgery, reducing the need for intense illumination sources that may damage biological tissues. While high transmission is vital for capturing the desired signal, blocking out-of-band light is equally important for reducing noise and enhancing contrast. SWIR filters achieve deep blocking, often at optical density levels of six or higher, which corresponds to reducing out-of-band light by a factor of 1 million. Blocking is critical in biomedical imaging systems that must isolate weak signals, such as fluorescence, from strong sources of noise. In fluorescence imaging, the excitation light used to activate fluorescent markers is always orders-of-magnitude more intense than the emitted fluorescence signal. Without effective blocking, this excitation light would overwhelm the detector, making it impossible to isolate the signal of interest, such as that of trace molecules. The steepness of the spectral transition between transmission and blocking is a key factor in achieving effective noise reduction. Filters with steep transitions can isolate signals more precisely, making them invaluable in applications where even minor leakage of unwanted light could compromise imaging quality. Transmission and blocking are two of the most important characteristics of an optical filter designed to operate in the SWIR, but other performance considerations must be accounted for as well for integration into a system. For example, in real-world applications, light rarely enters a filter at an exact perpendicular angle. Many systems, including surgical imaging setups and drone-mounted cameras, operate with wide cone angles where light approaches the filter at various inclinations. Designing the filters for angular stability under high cone-angle circumstances ensures their spectral performance regardless of the angle of light incidence. Designing filters to meet these needs while maintaining steep transitions and high blocking is a significant technical challenge. Achieving this balance requires advanced deposition techniques, such as sputtered deposition of thin-film coatings and innovative material combinations, which ensure that filters meet the demands of various biomedical and industrial applications. SWIR in biomedicine The adoption of SWIR imaging in biomedical imaging has accelerated during the past decade, due to the advancements in component technology. As SWIR technology has become more accessible, its use in areas including surgical imaging, diagnostics, and even environmental monitoring have expanded. One of the most transformative uses of SWIR imaging is fluorescence-guided surgery (opening image). In complex procedures, such as neuroblastoma removal, fluorescent markers that emit in the SWIR range enable surgeons to clearly distinguish tumor margins from healthy tissue1. Unlike visible light, SWIR penetrates deeper into tissue layers and avoids interference from scattered light, offering high-contrast imaging that allows for precise identification and removal of malignant cells. This capability reduces the risk of leaving behind residual tumor tissue and minimizes damage to healthy structures. Similarly, SWIR imaging has proved to be invaluable in other challenging surgical contexts, such as pancreatic and cardiovascular procedures, in which precise visualization of tumor boundaries and critical anatomical features is essential. In cancer therapy, SWIR imaging has emerged as a powerful tool for ensuring the precise delivery of therapeutic agents. By visualizing how drugs interact with tissues in real time, clinicians can assess the efficiency of delivery and make necessary adjustments to treatment plans. This level of precision reduces side effects and maximizes therapeutic efficacy. For example, SWIR imaging systems can detect the accumulation of therapeutic agents within a tumor, allowing clinicians to monitor the progression of treatment and make evidence-based decisions to improve outcomes2. Beyond the lab and operating room, SWIR imaging is driving innovation in noninvasive diagnostic tools, offering enhanced contrast and sensitivity for real-time medical assessments. One compelling example is the use of SWIR imaging for vascular monitoring, where it enables high-contrast visualization of blood flow through microvasculature. This capability, demonstrated with FDA-approved indocyanine green (ICG), allows for noninvasive imaging of brain and limb vasculature with superior contrast compared with traditional near-infrared (NIR) imaging. Another significant application is in hepatobiliary diagnostics, where SWIR imaging facilitates real-time tracking of ICG clearance through the liver and into the small intestine. This provides valuable insights into liver function and metabolic processes, enhancing diagnostic accuracy and patient monitoring3. The portability of modern SWIR imaging devices makes these applications particularly valuable in remote or resource-limited settings, where access to advanced diagnostic technologies is often limited. By leveraging the deep tissue penetration and low background noise of SWIR wavelengths, these emerging applications are expanding the capabilities of noninvasive diagnostics and enhancing patient care. Beyond biomedicine While biomedicine serves as a cornerstone for SWIR imaging, the versatility of SWIR-based imaging systems extends into several other fields that intersect with medical and life sciences applications. These complementary applications illustrate the broader relevance of the technology while reinforcing its importance in advancing scientific understanding. In remote sensing and environmental monitoring, SWIR imaging acts as a powerful tool for assessing the health of ecosystems and agricultural environments. For example, the ability to differentiate between subtle spectral features in the SWIR range allows researchers to monitor crop health, detect water contamination, and analyze atmospheric conditions. These applications provide crucial insights that inform public health, food safety, and environmental sustainability. The emergence of low-cost platforms such as PiMICS — a multispectral camera operating on a Raspberry Pi developed by a collaboration bridging continents with the International Commission for Optics — demonstrates how accessible multispectral imaging technology can advance sustainable development goals (Figure 3). Such innovations are particularly effective in resource-constrained settings, where traditional SWIR imaging systems have been prohibitively expensive for local researchers. Figure 3. Front and rear views of PiMICS zero. It has 14 3-W LEDs for active illumination and 15 narrowband filters for passive illumination of objects. Courtesy of John C. Howell. Additionally, SWIR technologies are being implemented in space-based applications, including satellite communication systems. Satellites equipped with SWIR filters play a pivotal role in imaging and communication systems, offering insights into planetary geology, atmospheric conditions, and extraterrestrial biology. The extreme conditions of space demand filters that maintain performance despite radiation, vacuum exposure, and temperature fluctuations. Although this application may seem removed from biophotonics, the technological advancements driven by aerospace research often inform medical and scientific innovations. Emerging trends One of the most significant trends in SWIR imaging is the continued reduction in costs for SWIR imaging system components. Early systems were prohibitively expensive due to the fabrication costs of sensors, limiting their use to well-funded research institutions. Currently, advancements in manufacturing and materials science have made SWIR technology more affordable, enabling adoption by smaller labs, clinical institutions, and field-based applications. Looking ahead, the integration of SWIR with other spectral imaging modalities will likely unlock even greater potential in biomedical diagnostics, precision surgery, and pharmaceutical research. As filter designs continue to evolve to accommodate wider cone angles and more demanding application requirements, SWIR imaging will become an even more powerful tool for researchers and clinicians. Additionally, new developments in quantum dot and organic photodiode sensors could further decrease costs while enhancing performance, making high-contrast, deep-tissue imaging even more accessible. Such research is underway in Belgium, where a research collaboration called Q-COMIRSE, including imec, Ghent University, QustomDot BV, ChemStream BV, and ams OSRAM, announced a prototype of a SWIR image sensor made with indium arsenide quantum dots last year. This prototype demonstrated that it is possible to make such sensors without toxic metals, and the prototype produced quality 1390-nm imaging results. By overcoming traditional imaging limitations, such as light scattering, autofluorescence, and signal interference, SWIR is providing researchers and medical professionals with deeper, clearer, and more precise insights than ever before. As innovation continues, SWIR imaging will play an increasingly vital role in improving patient outcomes, advancing scientific discovery, and solving real-world challenges in medicine, environmental science, and industry. Meet the authors Brian Manning, Ph.D., is senior application scientist at Chroma Technology Corp. After receiving a Ph.D. in anatomy and neurobiology at the University of Vermont and a postdoctoral fellowship at Massachusetts Eye and Ear Infirmary, Manning developed an expertise in numerous methodologies in his 19 years at Chroma, including, but not limited to, fluorescence microscopy, Raman spectroscopy, and flow cytometry; email: bmanning@chroma.com. Brandon Fowler is a marketing specialist at Chroma Technology Corp., where he brings more than 20 years of experience in optical fabrication, manufacturing, and quality management to translate complex photonics concepts into clear, accessible communication; email: bfowler@chroma.com. References 1. L. Privitera et al. (2023). Shortwave Infrared Imaging Enables High-Contrast Fluorescence-Guided Surgery in Neuroblastoma. Cancer Res, Vol. 83, No. 12, pp. 2077-2089. 2. J. Shah et al. (2020). Shortwave Infrared-Emitting Theranostics for Breast Cancer Therapy Response Monitoring. Front Mol Biosci, Vol. 7, p. 569415. 3. J. Carr et al. (2018). Shortwave infrared fluorescence imaging with the clinically approved near-infrared dye indocyanine green. Proc Natl Acad Sci USA, Vol. 115, No. 17, pp. 4465-4470.
